lens perspective question?

[stradibarrius]

If I had a 135 format lens of a given focal length, say 50mm, and had the equivalent focal length in medium format and in 4x5, would there be a difference in the overall perspective or "the way the print looks"???
This is assuming of course that the subject, the shooting position, the time of day, f/stop, the film, the paper and everything else were the same.
I am not asking if one print would be "better" or not only if there would be a difference in how the final print looked comparing the 3 formats.
If there is a difference can you try to explain what the difference would be?

Again, I am not asking if one format is superior to another, only if they would look different?

[Jim Jones]

The perspective would be about the same.

[timparkin]

The perspective would be about the same.

s/about/exactly/

[Brian Ellis]

I'm not sure how you're using the term "perspective" but without cropping I don't know how you'd make a print from 35mm film look like a print from 4x5 considering the different aspect ratios. Ditto for "medium format" depending on exactly what medium format you mean (e.g. 645, 6x6, 6x7, etc.). But perhaps I don't understand your question.

[BetterSense]

Lenses do not 'have perspective'. Perspective has nothing to do with lenses, only with where you stand compared to where the subject is.

We can't really address your question until everyone agrees what we are talking about.

[E. von Hoegh]

Lenses do not 'have perspective'. Perspective has nothing to do with lenses, only with where you stand compared to where the subject is.

We can't really address your question until everyone agrees what we are talking about.

+1.To continue, a 90mm lens and a 300mm lens will give the same perspetive, if used on the same format and at the same location. If the negative from the 90 is cropped, the prints will be identical.

[Steve Smith]

Lenses do not 'have perspective'. Perspective has nothing to do with lenses, only with where you stand compared to where the subject is.

+2

Perspective is dependent on your position relative to the subject. Your choice of lens and format controls which rectangle of reality gets recorded on the film.


Steve.

[E. von Hoegh]

If I had a 135 format lens of a given focal length, say 50mm, and had the equivalent focal length in medium format and in 4x5, would there be a difference in the overall perspective or "the way the print looks"???
This is assuming of course that the subject, the shooting position, the time of day, f/stop, the film, the paper and everything else were the same.
I am not asking if one print would be "better" or not only if there would be a difference in how the final print looked comparing the 3 formats.
If there is a difference can you try to explain what the difference would be?

Why don't you take a 35mm with a 50mm lens, and your 5x4 with a 150mm lens, and find out for yourself?

Again, I am not asking if one format is superior to another, only if they would look different?

[Ken Lee]

As others have pointed out, perspective depends on distance only - but that's an over-simplification of sorts.

Lets say we make a photo of an automobile, and we want to fill the frame with the car. We put a 50mm lens on our 135 camera, and we stand 12 feet from the car. With a 4x5 camera and a 150mm lens, we can also stand 12 feet from the car, and fill the frame.

Because we are standing 12 feet from the car in both cases, the perspective will be the same in both shots.

Now let's put a "wide angle" lens on the 135 camera: a 25mm lens. To fill the frame now, we need to stand 5 feet away. With the 4x5 camera, we change to a 75mm lens, and to fill the frame, we stand 5 feet away.

Because we are standing 5 feet away in both cases, the perspective will be the same in both shots.

As a rule of thumb, lenses for 4x5 are 3x the length of lenses for 135.

[Ken Lee]

Subjects appear "flat" when we view them from far away. Subjects appear "foreshortened" when we view them close.

Consider a portrait: From 6 inches away, the 2-inch distance from the nose to the eyes is considerable. From 60 feet away, that same 2-inch distance is negligible.

[jb7]

If I had a 135 format lens of a given focal length, say 50mm, and had the equivalent focal length in medium format and in 4x5, would there be a difference in the overall perspective or "the way the print looks"???

Equivalent focal lengths are usually calculated at infinity. Larger formats produce larger magnifications, so the equivalence breaks down at around portrait distance, where the lens is substantially racked out. If a 300mm on 4x5 is roughly the equivalent of an 85mm on 35 at infinity, the same lens at portrait distance might behave more like a 110mm, depending on the magnification used.

Perspective is wholly dependent on where you place the lens, rules for equivalence between formats break down as soon as you focus closer than mid distance. Angle of view will get narrower-

[Jeffrey Sipress]

I have a feeling the OP meant to say 'angle of view' or 'coverage' instead of perspective. I agree with the numerous posters who defined the term perspective.

[Bob Salomon]

We were taught perspective differently. We were taught that it changes with the angle of the camera to the subject. So:

Take a shot on any format with any lens at any distance. Move closer or further away, change lenses or change formats and the perspective remains the same.

Now take that first shot standing upu. Take a second one while kneeling from exactly the same spot with the same lens and camera of the same subject area. Now you have changed the perspective.

[stradibarrius]

Obviously I used the wrong word "perspective". I know better and I muddied up the question by using it in that way.
By taking the shot from exactly the same place at the same height etc. the "perspective" on all three shots would be the same.

The reason I asked the question was because I read a comment on a photo that had been taken with a 4x5 camera on one of the photo posting sites. The commenter said something to the effect that the 4x5 format has such a beautiful DOF???
I don't know what that means relative to other formats and was trying to find out if the statement had any basis in fact or if the poster just "felt" there was a difference?

[E. von Hoegh]

Obviously I used the wrong word "perspective". I know better and I muddied up the question by using it in that way.
By taking the shot from exactly the same place at the same height etc. the "perspective" on all three shots would be the same.

The reason I asked the question was because I read a comment on a photo that had been taken with a 4x5 camera on one of the photo posting sites. The commenter said something to the effect that the 4x5 format has such a beautiful DOF???
I don't know what that means relative to other formats and was trying to find out if the statement had any basis in fact or if the poster just "felt" there was a difference?

The poster might not know what he's talking about. DOF is a function of focal length, reproduction ratio, and aperture, and is readily quantified.

[Steve Smith]

The poster might not know what he's talking about.

Not quite. If you take two photographs from the same place, one with a 35mm camera and one with 5x4 and each was fitted with a lens which gives the same angle of view and the same aperture setting was used on both, the 35mm shot would have much more depth of field than that of the 5x4.


Steve.

[E. von Hoegh]

Not quite. If you take two photographs from the same place, one with a 35mm camera and one with 5x4 and each was fitted with a lens which gives the same angle of view and the same aperture setting was used on both, the 35mm shot would have much more depth of field than that of the 5x4.


Steve.

I'm very well aware of that; I stated it in my post. "Focal length" and "Reproduction ratio".

[Heroique]

...The reason I asked the question was because I read a comment on a photo that had been taken with a 4x5 camera on one of the photo posting sites. The commenter said something to the effect that the 4x5 format has such a beautiful DOF. I don’t know what that means relative to other formats...

I agree w/ most of the posts above about perspective (and strenuously disagree with a few of them!), but maybe I can give one more example – an oversimplified one – to help explain the “beautiful DOF” remark by the commentator you’ve quoted:

The DOF w/ a 180mm lens on a 35mm camera will be the same as the DOF w/ a 180mm lens on a 4x5 camera at the same position.

However, if you want the two compositions to fill the frame in a similar way (which might be more difficult than one thinks, since the two aspect ratios are different), the 35mm camera is going to have to be further away.

Let’s say you do this – move the 35mm camera further away, to make its composition look somewhat similar to the 4x5 camera’s composition.

Doing this, of course, gives the 35mm composition “more” DOF because you’ve moved further away.

I suspect the commentator you’ve quoted thought the 4x5 composition had “such a beautiful DOF” simply because it was shallower, throwing the background into greater blur, which was found to be more subjectively pleasing.

[Jeffrey Sipress]

We were taught perspective differently. We were taught that it changes with the angle of the camera to the subject. So:

Take a shot on any format with any lens at any distance. Move closer or further away, change lenses or change formats and the perspective remains the same.

Now take that first shot standing upu. Take a second one while kneeling from exactly the same spot with the same lens and camera of the same subject area. Now you have changed the perspective.


Sorry, Bob, that is a misconception that many very knowledgeable photography instructors spend their lives trying to correct. With so many photographers at differing levels of experience these days, the term perspective is used to mean whatever any person is trying to say. What YOU are doing is changing the composition. True perspective, the relationship among elements within a scene, is a factor of camera to subject distance.

[Dan Fromm]

Not quite. If you take two photographs from the same place, one with a 35mm camera and one with 5x4 and each was fitted with a lens which gives the same angle of view and the same aperture setting was used on both, the 35mm shot would have much more depth of field than that of the 5x4.


Steve.Not true if the final prints are the same size.

[Bob Salomon]

Sorry, Bob, that is a misconception that many very knowledgeable photography instructors spend their lives trying to correct. With so many photographers at differing levels of experience these days, the term perspective is used to mean whatever any person is trying to say. What YOU are doing is changing the composition. True perspective, the relationship among elements within a scene, is a factor of camera to subject distance.

And in photo school in the early 60's that was the explanation of perspective at that time. We were not only explained it, we were assigned to illustrate it.

But that was in the dark ages compared to most experiences today. Like the definition of Pluto not being a planet. Anything can change over time! In sixth grade Mrs. Vetter took the better part of a morning one spring day in 1954 to make sure that we all understood why man could never go to the moon!

[Ken Lee]

Bigger film/sensor requires longer lenses. Longer lenses - at the same aperture - have less depth of field than shorter lenses.

How much less ? When we double the focal length, we have to stop the lens down by 2 f-stops, to get the same depth of field.

For a 100mm lens to match the depth of field of a 50mm lens at f/16, we need to shoot the 100mm lens at f/32.

[SergeiR]

And in photo school in the early 60's that was the explanation of perspective at that time. We were not only explained it, we were assigned to illustrate it.

But that was in the dark ages compared to most experiences today.

Meh. This is exactly how i still illustrate it to me students any time i see them shooting full body or 3/4 portrait from the shoulder level.
That said - i cant for the life of me remember how we been taught perspective in art school and later in school. Merciful nature wiped most of that stuff out.

[rdenney]

Bob, I learned perspective as a draftsman, not as a photographer. Perspective is the relationship in size between near objects and far objects. That is affected only by the distance between the observer and those objects.

Perspective exists in all three spatial dimensions, of course. When you raise your position, you have changed your observation point in at least one of those dimensions, and that will change perspective.

Now, when we project that three-dimensional space onto two-dimensional film, what we interpret as perspectives shows up as converging parallel lines.

We can distort those converging lines by tilting the film with respect to the scene, and if we are clever, our distortion can cancel out the convergence. When we turn the camera, we are tilting the film with respect to the scene, and it alters the way those lines appear to converge. We call that a change in perspective, but it is really just a trick that has the appearance of a change in perspective.

Convergence happens only when three-dimensional space is projected onto a surface. It does not affect the apparent size of near and far objects from an observer's location.

Now, on the depth-of-field thing.

If we take a 300mm lens and put it on an 8x10 camera, and make a photo of a person's face such that it nearly fills the frame, we have a full-face portrait with a given depth of field. If we take that same lens (along with the same aperture setting) and put it on a 35mm camera (using, say, a bellows), we will get exactly the same depth of field and perspective, if both are printed to the same magnification.

But the picture from the 35mm camera will only include the subject's nose, not the whole face. And if we print to the same magnification, the print from the 8x10 camera will be over 8 times bigger in width and height than the print from the 35mm camera. If we enlarge the 35mm picture to the same print size, the depth of field will actually be less. But that nose will be a lot bigger.

When we change the lens on the 35mm camera to provide a similar view as we got using the 300 on the 8x10 camera, we might end up using something like a 45mm lens. That will give us that full-face framing. Since we put the camera in the same location, the perspective will be the same. But the 45mm lens has greater depth of field than the 300mm lens, when both are printed to the same size.

Since we usually base comparisons on similar subject framing shot from similar locations, the focal lengths will be different. Thus, for convenience, I approximate equivalent apertures (for general depth-of-field effects) as being two stops per major format change. Going from 35mm to 6x9 requires two stops smaller to achieve the same depth of field. Going to 4x5 requires two more, and going from there to 8x10 requires two more. Like all such approximations, it's not precise. But it provides a starting point.

Rick "noting that a 300mm f/5.6 lens on 8x10 can produce an effect when used wide open not possible on 35mm with any available lens" Denney

[rdenney]

Meh. This is exactly how i still illustrate it to me students any time i see them shooting full body or 3/4 portrait from the shoulder level.
That said - i cant for the life of me remember how we been taught perspective in art school and later in school. Merciful nature wiped most of that stuff out.

You are actually changing the camera position with respect to the vertical dimension when you go from sitting to standing. So, you are changing the perspective relationships, but only in the vertical dimension.

This is one of the key changes in event photography between 50 years ago, when Rolleiflexes and Hasselblads--used at waist-level--ruled such photography, and 25 years before that, when press cameras were mostly used at eye level, and now, when DSLR's are used at eye level.

Rick "everyone is right" Denney

[Heroique]

...Now, when we project that three-dimensional space onto two-dimensional film, what we interpret as perspectives shows up as converging parallel lines. We can distort those converging lines by tilting the film with respect to the scene, and if we are clever, our distortion can cancel out the convergence. When we turn the camera, we are tilting the film with respect to the scene, and it alters the way those lines appear to converge. We call that a change in perspective, but it is really just a trick that has the appearance of a change in perspective...

Can everybody please note this important point – it will eliminate a lot of pain in future discussions.

Rick is describing a “change in perspective” that really isn’t a change in perspective – that is, rendering converging lines straight, as one does w/ back tilt (for vertical lines) or back swing (for horizontal lines).

I think one of our longest-ever threads – about perspective, of course – suggested that we call this type of perspective “geometric perspective,” to distinguish it from “viewpoint perspective,” the other kind that changes with camera/lens position.

I think Doremus came up w/ those terms, a good idea.

[Steve Smith]

Not true if the final prints are the same size.

I disagree with that statement.


Steve.

[SergeiR]

You are actually changing the camera position with respect to the vertical dimension when you go from sitting to standing. So, you are changing the perspective relationships, but only in the vertical dimension.


Projection control. Nowdays people like to call it "perspective's distortion"

[Mark Sawyer]

Not true if the final prints are the same size.

I think you're off on this one, Dan. One can't change the depth of field in a negative by printing it larger/smaller.

[rdenney]

I think you're off on this one, Dan. One can't change the depth of field in a negative by printing it larger/smaller.

You don't change what's on the negative, but you sure do change the size of the maximum circle of confusion that defines what is acceptable depth of field.

Rick "but more concerned about gross effects than fine effects when comparing aperture effects across formats" Denney

[rdenney]

Projection control. Nowdays people like to call it "perspective's distortion"

Projection control is when you tilt the back to either minimize or exaggerate convergence.

But when you raise the camera, your camera is now closer to the top of the subject's head, and farther from the subject's feet. That's a real change in position that will change the vertical perspective. And if the head is in the same position within the frame, then you have to change the up and down aiming of the camera, and that will also change projection.

I do like the use of the term "projection effects" to describe what we do with how we angle the image plane, versus "perspective" to describe what we do with lens (i.e. observation) position.

Rick "who grew up wanting to be an architect, and learned to draft mechanical perspectives at age 10" Denney

[Steve Smith]

Depth of field is defined by the magnification at the film plane. The size you print the image will not have an effect. If an image has the subject in sharp focus and the background blurred, the background will not come into focus by printing smaller (or larger) in the same way that a projected, slightly out of focus slide can not be brought into focus by adjusting the projector's lens.

For a similar field of view taken at the same aperture, the intermediary negative step to go from scene to print has an effect. If the film (or sensor) is tiny, it will have huge depth of field, even at small f No.s. If it is a large piece of film, it will have much less.


Steve.

[Mark Barendt]

The reason I asked the question was because I read a comment on a photo that had been taken with a 4x5 camera on one of the photo posting sites. The commenter said something to the effect that the 4x5 format has such a beautiful DOF???
I don't know what that means relative to other formats and was trying to find out if the statement had any basis in fact or if the poster just "felt" there was a difference?

The perceived DOF is a product of focal length and aperture.

Lenses simply don't care what film is behind them; a 150mm lens, at a given aperture, provides the same DOF on either 35mm or 4x5 or any other format.

The film or sensor simply defines one particular crop out of what the lens actually projects. Larger formats "see" more (crop out less) of what the lens projects.

In typical use a short lens (say a 50mm) will have a longer DOF than a long lens (a 150 for example); you could theoretically match DOF using aperture but that isn't normally practical, preferable, or even possible in the real world.

In practical terms your question is trying to get the same crop (photo) from a given scene using different format cameras; to match the "crops" the focal length has to change. Smaller formats must use shorter lenses than larger formats to get the "same" photo so smaller formats typically provide more DOF.

[SergeiR]

Projection control is when you tilt the back to either minimize or exaggerate convergence.

Exactly what you do with simple camera (that doesn't have rear standard tilt) when you shooting from above/below.
You tilt you front and read standard at same time (aka - just tilting camera).

People know how to level horizon. They now even have electronic horizons built in cameras.
But when they recompose and go higher/lower - they point camera upwards/downwards a bit. Not much, but its getting more pronounced wider the lens go.

In fact that do it with cameras that do have movements too ;) I know, i do use that, when legs extended towards camera a bit.

--

Anyway - this has drifted waaay away from DOF that apparently whole thing was about originally.

[Steve Smith]

Lenses simply don't care what film is behind them; a 150mm lens, at a given aperture, provides the same DOF on either 35mm or 4x5 or any other format.

Indeed. But to get the same field of view on a larger format, a longer lens is needed and this leads to smaller depth of field.


Steve.

[Mark Barendt]

Indeed. But to get the same field of view on a larger format, a longer lens is needed and this leads to smaller depth of field.

Steve.

I thought I said that.

;)

Have some more coffee Steve and I'll work on my English while you do.

[Steve Smith]

I thought I said that.

Yes, you did. Sorry. I was using the information in your post to back up something I wrote yesterday which was disputed rather than argue with you!


Have some more coffee Steve and I'll work on my English while you do.

Coffee? I'm English and have therefore just made myself some tea.


Steve.

[SergeiR]

Coffee? I'm English and have therefore just made myself some tea.

yes, but very modern, apparently

[Jim Jones]

Depth of field is defined by the magnification at the film plane. The size you print the image will not have an effect. If an image has the subject in sharp focus and the background blurred, the background will not come into focus by printing smaller (or larger) in the same way that a projected, slightly out of focus slide can not be brought into focus by adjusting the projector's lens.

For a similar field of view taken at the same aperture, the intermediary negative step to go from scene to print has an effect. If the film (or sensor) is tiny, it will have huge depth of field, even at small f No.s. If it is a large piece of film, it will have much less.


Steve.

Depth of field calculations are usually based on a specified circle of confusion at the film plane rather than on the COF in the print. The degree of enlargement certainly has an effect on both the COF the apparent DOF unless the print is always viewed at a distance to ensure consistant persepctive. This is rarely the case.

[Brian Ellis]

I disagree with that statement.


Steve.

And IMHO you're right to disagree because there are only three factors that affect depth of field - aperture, focal length, and camera-to-subject distance. In the situation you described the focal length of the lens for the 35mm camera would have to be considerably shorter than the 4x5 lens in order to present the same angle of view when both photographs are made from the same distance. Shorter focal length = greater depth of field, all other things affecting depth of field (i.e. aperture and subject distance) being equal.

Depth of field is a function of the size of the circles of confusion in the negative. Reproduction ratio affects the perception of "sharpness" in a print (along with other variables such as print viewing distance). But it doesn't affect depth of field as such. Maybe it's just a question of semantics but to me it's more accurate to relate depth of field to size of the circles of confusion in the negative since that's fixed once lens, aperture, and subject distance are chosen, not to how sharp a print appears since that depends on a number of variables of which size of circles of confusion in the print (i.e. reproduction ratio) is one but not the only one.

[rdenney]

Maybe it's just a question of semantics...

Let's say it this way: degree of enlargement does not change the size of the fuzzy spots on the film, but it does affect the point at which their size becomes intolerable. It's the difference between "depth of field" and "acceptable depth of field".

Rick "observing that many visual artists are concerned with semantics to an ironic degree" Denney

[Leonard Evens]

As others have pointed out, "perspective" usually refers to the position of the lens with respect to the subject. If you place the lens in the same position, and take a picture of the same subject, you will get the same perspective whatever the film format or the focal length of the lens. But the print you make will depends on other things, e.g., the format used, the focal length, and how the picture is cropped, as well as other factors such a depth of field, which will also depend on the format and lens focal length as well as the f-stop used.

[Jeff Keller]

The end result is that if you use a different format to cover the same angle of view, you will use a different focal length. A different focal length will require a different aperture to get close to the same DOF. Even if you pick the appropriate aperture to give the equivalent DOF, it is likely that near/far edges of DOF will be slightly different (DOF calculations assume simple lens geometry generally far from macro). A different aperture will require a different shutter speed. Aperture blades are different for different lenses. Leaf shutters are different from focal plane shutters.

The image will be different perhaps not just a subtle difference.

Jeff Keller

[Bob Salomon]

The end result is that if you use a different format to cover the same angle of view, you will use a different focal length. A different focal length will require a different aperture to get close to the same DOF. Even if you pick the appropriate aperture to give the equivalent DOF, it is likely that near/far edges of DOF will be slightly different (DOF calculations assume simple lens geometry generally far from macro). A different aperture will require a different shutter speed. Aperture blades are different for different lenses. Leaf shutters are different from focal plane shutters.

The image will be different perhaps not just a subtle difference.

Jeff Keller

Let's assume that you have an Apo Sironar S 210mm in Copal 1 shutter.

Let's also assume that you have a TechniKardan 69 and a TechniKardan 45 as well as a Super Technika V 57 and a Kardan Standard 810.

That 210 Apo Sironar-S covers each of those formats so there is no reason why a photographer could not use that one lens and have a long focal length on 69, a short telephoto on 45, a normal on 57 and a wide on 810 and shoot the same scene with all at the same exposure. That means the same aperture and since it is one shutter, all the blades are the same.

[Mark Sawyer]

You don't change what's on the negative, but you sure do change the size of the maximum circle of confusion that defines what is acceptable depth of field.

Rick "but more concerned about gross effects than fine effects when comparing aperture effects across formats" Denney

Technically correct, but only on the scale of "if you make it small enough, no one can tell it's out of focus."

[rdenney]

Depth of field is not about what is in focus. It is about what appears, at some given magnification (including the magnification resulting from enlargement), sharp enough to look as though it is in focus.

Only what's in the actual focus plane is "in focus."

Rick "depth of field is all about apparent sharpness" Denney

[Heroique]

Only what's in the actual focus plane is "in focus."

How can anything be “in” the focus plane when it’s two dimensional?

;^)

[E. von Hoegh]

How can anything be “in” the focus plane when it’s two dimensional?

;^)

I think "plane" is, by definition, a two dimensional surface....

[Mark Barendt]

So "at" the plane of focus instead of "in".

I think Heroique was poking a bit of fun at the conversation. :rolleyes:

[E. von Hoegh]

So "at" the plane of focus instead of "in".

I think Heroique was poking a bit of fun at the conversation. :rolleyes:
Or "on". But "in" works perfectly well.

[Steve Smith]

In... On... I prefer in the neighbourhood of.


Steve

[E. von Hoegh]

In... On... I prefer in the neighbourhood of.


Steve

That works, too. We're talking photography, not Euclid.

[BetterSense]

Depth of field is defined by the magnification at the film plane.

Well you can define it however you want, but defining it that way is pretty useless unless the unenlarged negative is your final output. The only sensible definition is based on the print. Have you ever noticed that published tables for 'film CoC' are different for different formats? That's because the print CoC is the SAME. Despite your assertion, depth of field is defined by magnification of the FINAL PRINT. The fact that 'film CoC' tables have different values for different formats is a direct result of this.


Maybe it's just a question of semantics but to me it's more accurate to relate depth of field to size of the circles of confusion in the negative
Well if you are going to use a nonstandard and un-useful definition of depth-of-field, make sure everyone knows. The only person in the world who might care about DOF of the negative is the printer...and I don't even know why he would care.

In terms of thin-lens optics, format size is irrelevant to DOF. In real life, the results can be affected by diffraction, since the apertures used in enlarging/processing small formats may introduce more diffraction than larger ones used for larger formats.



The size you print the image will not have an effect.
See above. The print CoC (a terrible unit, IMO) is defined at a certain viewing distance. Since depth of field in photography is defined off of print CoC, print size has a direct, drastic effect on depth-of-field. I wish that we defined depth-of-field in terms of arc-seconds (because small prints are commonly viewed from a closer distance) but if wishes were horses, we'd all be eating steak.


there are only three factors that affect depth of field - aperture, focal length, and camera-to-subject distance.
Actually there are only two, besides print CoC, which is the same for all camera formats--magnification (that means final print magnification) and aperture . Different focal lengths give the same DOF at the same magnification.

[Steve Smith]

but defining it that way is pretty useless unless the unenlarged negative is your final output. The only sensible definition is based on the print.

I don't agree. If you set the camera up so you get a depth of field which starts at 15' in front of the camera and ends at about 20' then the prints will look similar whatever size you print them be it postcard size or a giant advertising sign.

Changing the print size won't expand or contract the depth of field as captured on the film.


Steve.

[rdenney]

In... On... I prefer in the neighbourhood of.

If we are going to match the pedanticism that is common on this forum, then one needs depth of field to handle the neighborhood.

Rick "responding in kind" Denney

[BetterSense]

If you set the camera up so you get a depth of field which starts at 15' in front of the camera and ends at about 20' then the prints will look similar whatever size you print them be it postcard size or a giant advertising sign.

There's no other way to put this, except that it's wrong. Very wrong. Not just slightly wrong, but wrong by definition.

It's not even possible to
set the camera up so you get a depth of field which starts at 15' in front of the camera and ends at about 20 without making an assumption about the final print size ahead of time. Otherwise, you cannot define what it means to have a certain depth of field.

[rdenney]

I don't agree. If you set the camera up so you get a depth of field which starts at 15' in front of the camera and ends at about 20' then the prints will look similar whatever size you print them be it postcard size or a giant advertising sign.

How do you propose to do that?

Tilting the lens with respect to the film has no effect on depth of field. It does tilt the focus plane, but the focus plane is still a plane and nothing more (assuming the lens has a flat field, of course, but even without that assumption the focus surface is a surface and not a volume). Depth of field is a wedge-shaped zone around that tilted focus plane, and the thin end of the wedge is the part of it closest to the camera. But away from the focus plane, things are not "in focus" and depend on depth of field--and on the standard by which depth of field is judged adequate--to appear sharp. And that standard is absolutely based on total magnification, including the magnification of enlargement.

Rick "whose neck hair stands on end when people talk about using camera movements to increase depth of field" Denney

[E. von Hoegh]

If we are going to match the pedanticism that is common on this forum, then one needs depth of field to handle the neighborhood.

Rick "responding in kind" Denney

I use Reimannian depth of field. Solves all these problems.

[Steve Smith]

O.K. Ignore the figures I used.

If you have a photograph with narrow depth of field such that foreground and distant objects are out of focus and the middle area is in focus, changing the print size will not expand or contract the apparent depth of field in the print.

Your hair need not stand on end as I was not referring to the use of camera movements.


Steve.

[cowanw]

This has puzzled me all my life. I will look with interest at the concensus. Although I expect we do need to define how close we stand to view the variously sized prints. I suspect the fact that COC is not a constant is the source of consternation.

"A different maximum circle of confusion also applies for each print size and viewing distance combination": Cambridge in colour.

[BetterSense]

If you have a photograph with narrow depth of field such that foreground and distant objects are out of focus and the middle area is in focus, changing the print size will not expand or contract the apparent depth of field in the print.

You are wrong. Changing the print size WILL expand or contract the apparent depth of field in the print. Magnification is, in fact, part of how depth-of-field is defined. It's physics and geometry. You cannot simply wish the magnification term out of the thin-lens depth-of-field equation.

Honestly, I'm surprised this is not obvious. Who among us has not printed an apparently-sharp 35mm contact print, only to find out that it looks OOF at 8x10? Why do we use loupes on our ground glass? According to your statement, if it looks sharp at 4x5 it should be sharp at any size.


"A different maximum circle of confusion also applies for each print size and viewing distance combination": Cambridge in colour.

Absolutely! Depth of field has no meaning outside the context of VIEWING. That is why it is defined, from the beginning, using magnification, which is obviously important when it comes to perception of details (else we would have never invented the microscope). When it comes to viewing reflective media, the circle of confusion has to be CHOSEN based on visual perception. It could be .5mm or it could be 4 inches. Once you have chosen a circle of confusion for the print, THEN you can meaningfully talk about depth of field when taking photographs. Circles of confusion at any intermediate stage (such as on the camera film) is basically irrelevant. You could shoot to a small format and enlarge 10x or shoot to a format twice as big and enlarge 5x. The 'film CoC' will be different in each case but the depth of field will be the same.

At at agreed-upon print CoC, all photographs taken at the same aperture (as distinct from f-stop) and enlarged to the same magnification will have the same depth of field characteristics, completely regardless of lens focal length, film format, or whether you are using 8mm or 20x24 film.

[E. von Hoegh]

This has puzzled me all my life. I will look with interest at the concensus. Although I expect we do need to define how close we stand to view the variously sized prints. I suspect the fact that COC is not a constant is the source of consternation.

"A different maximum circle of confusion also applies for each print size and viewing distance combination": Cambridge in colour.

Be sure to apply your tetrapyloctomy filter. (winking smiley)

[Steve Smith]

I think this comment on Luminous Landscape gets it right!


Circle of Confusion (COF)
Definition: "A group of photographers sitting around trying to understand Depth of Field"


Steve.

[E. von Hoegh]

I think this comment on Luminous Landscape gets it right!




Steve.
Perfect!

[RichardSperry]

At at agreed-upon print CoC, all photographs taken at the same aperture (as distinct from f-stop) and enlarged to the same magnification will have the same depth of field characteristics, completely regardless of lens focal length, film format, or whether you are using 8mm or 20x24 film.

This may be true(and what Bob Solomon wrote a out the 210 lens) is true. It's not really useful in a practical sense.

If you take a photo of a person(or subject) that fits in the small format, he/it will be entirely so small on the large format that he/itwill be lost. People don't photograph in such a vacuum, they will move the camera or the subject to fill the frame(they usually change the lens though).

And when that happens, that changes the whole picture.

In Bob's experiment, the only believably realistic people who would photograph this way are going to be people experimenting with depth of field, depth of focus, and perspective.

And that is only useful for people, the kind of people who take photos of test patterns, to prove that a lens does what it does. Which leaves the rest of us changing where the lens(or focal length of it) is to compose our photos normally, which will change the amount of out of focus regions of our photos.

The background blur of a 210 lens taking a head and shoulders photo of a person is going to look different when taken with a 35mm camera than it will with a 4x5 camera. Because the distance from the lens to the subject will change, if that doesn't change it's a completely different photo isn't it. One will be a head and shoulders portrait the other will be head to toe with a bunch of extra sky and grass included, but the background will be blurred equally then of course.

[RichardSperry]

And I don't know how much time I should put into reading and understanding BetterSense's post.

Maybe someone can translate it.

The apparent depth of field in a photo changes depending on how large it's printed?

Counterintuitive.

[Steve Smith]

And I don't know how much time I should put into reading and understanding BetterSense's post.


The apparent depth of field in a photo changes depending on how large it's printed?

I think that's what he is claiming and I am suggesting otherwise.

I think depth of field is dependent upon the magnification at the film plane, not including the final print size.



Try this test (don't actually try it, just think about it).

Take two cameras, one 35mm and the other, 5" x 4"
Put a 'normal' focal length lens on each of them such that the subject is framed equally by both.
Set the aperture to f8 on both lenses.
Focus on the same place with both (e.g. a subject's eyes).
Take a photograph with both.
Print both up to 8" x 10"

Which one has the least depth of field?

Why?


Steve.

[Helen Bach]

And I don't know how much time I should put into reading and understanding BetterSense's post.

Maybe someone can translate it.

The apparent depth of field in a photo changes depending on how large it's printed?

Counterintuitive.

Strange, because I find it completely intuitive and, as BetterSense points out, quite obvious in practice. It's not necessarily 'how large it's printed', but more like 'how large it is on your retina' of course - this allows for both print size and viewing distance.

Have you never had the experience of seeing the difference in apparent sharpness (which is what DoF is all about) between a contact print and an 8x enlargement, for example? Or something that looks pin sharp all over at 8x10 but shows a limited DoF at 32x40?

If you disagree with BetterSense's post, doesn't that make it all the more worthwhile to try to read and understand it?

Best,
Helen

[Jim Jones]

At constant subject distance and print size, the only thing that affects the hyperfocal distance and DOF is the entrance pupil of the lens. Perhaps this will simplify the subject for those like me who don't handle formulae with the facility we did many decades ago.

[Brian Ellis]

Well you can define it however you want, but defining it that way is pretty useless unless the unenlarged negative is your final output. The only sensible definition is based on the print. Have you ever noticed that published tables for 'film CoC' are different for different formats? That's because the print CoC is the SAME. Despite your assertion, depth of field is defined by magnification of the FINAL PRINT. The fact that 'film CoC' tables have different values for different formats is a direct result of this.


Well if you are going to use a nonstandard and un-useful definition of depth-of-field, make sure everyone knows. The only person in the world who might care about DOF of the negative is the printer...and I don't even know why he would care.

In terms of thin-lens optics, format size is irrelevant to DOF. In real life, the results can be affected by diffraction, since the apertures used in enlarging/processing small formats may introduce more diffraction than larger ones used for larger formats. . .

I would think that anyone who makes a print would care about the negative. That's what you make the print from.

The size of the circles of confusion in the negative is one factor that determines how large the print can be made and still appear acceptably sharp (recognizing that different people have different standards of what's "acceptably sharp"). So for anyone who plans to print from a negative the size of the circles of confusion in the negative is important. Other things also affect "acceptable sharpness" such as the print magnification factor as you point out, viewing distance, the viewer's visual acuity, lighting in the display area, etc. etc. But that doesn't mean we lump them all together under the rubric "depth of field."

Diffraction has nothing to do with depth of field, nor does the aperture chosen for the enlarger lens (I guess that's the aperture you're talking about when you refer to "aperture used in enlarging/processing"). Both relate to the overall "sharpness" of the print, not to depth of field as such. See above paragraph.

With respect to your novel idea that only magnification and "aperture" affect depth of field, I'd suggest that you do some reading. Ansel Adams book "The Camera," at pp. 48-50, would be a good place to start. He discusses the three factors that affect depth of field (camera lens focal length, aperture, and distance from subject) and then discusses other things such as your favorite, i.e. print magnification, that all together determine how "sharp" a print is perceived to be.

[RichardSperry]

Or something that looks pin sharp all over at 8x10 but shows a limited DoF at 32x40?

Helen,

There are so many variables in his post, I don't understand his point.

One could take a photo. Blow it up to billboard size. When I view that image under a loupe, what I look at may appear sharp. It may only be the edge of a (6"x6")pixel or the edge of a grain but it should be sharp.

When I look at it from the freeway, the leaves behind the subject will appear out of focus as it was shot by the photographer. I can't imagine the apparent depth of field changing just because it is bigger.

The subject which is in focus does not go out of focus, or become sharper, because it is larger.

I will admit that it is all an optical illusion anyway, because at loupe distance or say 3 feet away it will all appear as incomprehensible circles or squares. I am too close to see what the whole photo looks like at that distance. But that is something entirely than the depth of field caught in the original photo.

I can't see that changing. If the subject is in focus, and something right behind him is just barely out of focus, and the leaves 12 feet behind him are blurred, out of focus, in the original small negative or contact print. Blowing it up would not change that. When we blow it up to billboard size the subject will remain in focus, the chair back behind him slightly blurred does not now "zoom" into more focus or less focus, and the leaves in the trees behind him remain blurred, they won't become less blurred or more in focus on our billboard.

That said, I have negatives that when looked at normally, with the eye, appear to have the subject in focus, but enlarged it becomes obvious that the focus plane, it was taken out of focus, is really in front of the subject. And the subject is really out of focus, and it's out of focus because it was taken that way, and would remain out of focus at any enlargement. The depth of field did not change, it's just a matter of the resolving power and limitations of the eye.

I could just as easily put my eye a millimeter away from your 8x10 or your 32x40 enlargements and they will both be equally visually incomprehensible.

[rdenney]

Try this test (don't actually try it, just think about it).

Take two cameras, one 35mm and the other, 5" x 4"
Put a 'normal' focal length lens on each of them such that the subject is framed equally by both.
Set the aperture to f8 on both lenses.
Focus on the same place with both (e.g. a subject's eyes).
Take a photograph with both.
Print both up to 8" x 10"

Which one has the least depth of field?

Why?


This is mixing two effects, which promotes confusion between the two, not clarity.

Small format has greater depth of field, because one uses a shorter lens compared to large format to make the same photo from the same camera position.

But a print of given size from small format has less depth of field because it is enlarged to a greater degree to make the same size print.

Try this experiment:

Take that 4x5 image, and make one contact print and one 16x20. View both from 10 inches. Things that seemed sharp in the contact print may not seem sharp in the 16x20, even if items in the focus plane seem sharp enough in both. That's because the fuzziness of some items not being quite in focus is smaller than one can detect in the contact print, but big enough to detect in the 16x20. It's not diffraction, or lens aberrations, or morning mist causing that difference. It's that the boundary between what is acceptable fuzziness caused by not being in the focus plane and what is unacceptable moves as you increase the size of the print.

Now, if the viewer adjusts his distance to both prints such that they present the same viewing angle, which will require the viewer to be four times the distance from the 16x20 as from the contact print, then enlargement size won't matter. But this notion of "proper viewing distance" only exists in two cases: 1.) when the viewer's position is physically enforced (as with the billboard example), and 2.) when the assumption of proper viewing distance is needed to win an argument.

Now, if the target of one's efforts is a given enlargement ratio, then there will be a maximum one of those for a given circle of confusion on the negative. We are coming at this question from opposite application philosophies. Many use large format to permit a larger print at a given enlargement ratio, but many others use it to create a particular effect of endless detail and tonality even in smaller prints. So, in some situations, it's relevant to compare at the same print size, and in other situations, it's relevant to compare at the same enlargement ratio. If one knows those two situations are different, the assumptions they make based on one situation won't set for them a trap when they find themselves in the other situation.

Rick "keeping separate effects separate" Denney

[Helen Bach]

...

The subject which is in focus does not go out of focus, or become sharper, because it is larger.

...

That's true, but DoF is not about things that are actually in focus, it's about things that only appear to be in focus: Things that are out of the focused plane, but the degree of blur is so slight that we can't resolve it as blur until it is enlarged sufficiently. The more we enlarge the blur circle the more chance there is that it appears to us as a blur circle and not a focused point.

Best,
Helen

[Steve Smith]

I think we are forgetting the question the OP asked (I'm sure he abondonned this thread ages ago!). After initially getting confused and asking about perspective, he realised that he actually meant depth of field and posted this:



The reason I asked the question was because I read a comment on a photo that had been taken with a 4x5 camera on one of the photo posting sites. The commenter said something to the effect that the 4x5 format has such a beautiful DOF???
I don't know what that means relative to other formats and was trying to find out if the statement had any basis in fact or if the poster just "felt" there was a difference?

With all other variables being equal (aperture, angle of view) then depth of field decreases with an increase in format size.


Steve.

[RichardSperry]

Helen,

Well, if that's what BetterSense meant then it's pretty useless. He's just entering viewing distance, and resolving power of the eye into the mix. That's all.

Just like if you put both of your enlargements up to your eye a millimeter away, you're not going to be able to make any sense out of what you see. Or drive 10 miles away from the billboard sized enlarged photo.

None of that practically, or usefully, changes the depth of focus or depth of field of the original photo.

I find that so intuitive to not even mention, and not counterintuitive like I stated previously.

I use a 25 power grain focusing scope to focus my negatives when I enlarge. I don't use it to tell if the "scene" is in focus. I use it to focus on the grain in the negative. Using that device, looking at the negative this way, many many times enlarged from the original size does nothing to change the depth of focus or depth of field captured on the negative.


That's true, but DoF is not about things that are actually in focus, it's about things that only appear to be in focus:

Then nothing is EVER really in focus anyway, it just appears in Focus. And focus does not then even exist. Which then negates any discussion of things are ever in focus, they can never really be in focus because focus does not exist really. I find this practically useless.

[rdenney]

Okay folks, I tried a formula by which all could maintain their point of view and be correct. I give up.

On the tuba forum, when a pedantic argument turns into repeated assertions that the other person is wrong, and perhaps even stupid, often including putting words in their mouth, someone will show a photo of beer, preferably served by persons who have earned the adjective "buxom", and that, shall we say, refocuses the average tuba player's priorities to more important things. What would that be here? A Deardorff so modeled?

Rick "whose beer-and-server photo choices are limited by the large format requirement" Denney

[Brian Ellis]

. . . Then nothing is EVER really in focus anyway, it just appears in Focus. And focus does not then even exist. Which then negates any discussion of things are ever in focus, they can never really be in focus because focus does not exist really. I find this practically useless.

In layman's terms - if the lens is properly focused there will be one plane along which all objects will be in focus. The things on that plane will appear as points on the film. Everything on either side of that plane will appear as circles. The farther from the plane, the larger the circles. Those things won't actually be in focus but if the circles are small enough they can be made to appear to be in focus. It's this total area of "adequate focus" that represents "depth of field." Which is what I think Helen meant when she said that depth of field isn't about things that are actually in focus, it's about things that only appear to be in focus. And of course she is, as usual, correct.

[RichardSperry]

RDenny,

I'm not trying to be pedantic.

I'm trying to figure out the writer's meaning, and then trying to find a use for it if it's true. That's all. Helen's posts are helping with that.

[RichardSperry]

In layman's terms - if the lens is properly focused there will be one plane along which all objects will be in focus. The things on that plane will appear as points on the film. Everything on either side of that plane will appear as circles. The farther from the plane, the larger the circles. Those things won't actually be in focus but if the circles are small enough they can be made to appear to be in focus. It's this total area of "adequate focus" that represents "depth of field." Which is what I think Helen meant when she said that depth of field isn't about things that are actually in focus, it's about things that only appear to be in focus. And of course she is, as usual, correct.

1) Real focus only exists on one plane. That plane has no depth dimension. Focus then is one plane thick, of no dimension.
2) Everything else is just varying degrees of blurriness.
3) The degree of blurriness is dependent upon the distance from the focus plane and the circles produced on the film or sensor.
4) Larger circles means further distance and more blur.
5) The circles can be so small they appear to be points.
6) Small circles appear in focus.
7) Small circles can become large circles when enlarged, and this become blurry. They are no longer small enough to be confused as points on an enlargement.


Question is does point 7 remain true if viewing distance changes proportionately to the enlargement?

[Mark Sawyer]

Viewed through eyeglasses smeared with vaseline, from more than one hundred yards away, or in complete darkness, all 8x10 prints look equally in focus. (Since there seems to be a brainstorming session going on for new variables to add to the DOF equation...)

[Steve Smith]

What about variations in drunken state of the viewer?


Steve.

[Mark Sawyer]

What about variations in drunken state of the viewer?


That too. I also find that a sharp blow to the back of the viewer's head can improve depth of field and appreciation of the artistic aesthetic...

Sooooo many variables...

( I imagine Peter Lik's stuff looks great on acid... )

[E. von Hoegh]

That too. I also find that a sharp blow to the back of the viewer's head can improve depth of field and appreciation of the artistic aesthetic...

Sooooo many variables...

( I imagine Peter Lik's stuff looks great on acid... )

Unfortunately, it's hard to find really pure acid around here. How about Gursky? Psilocybin?

[cowanw]

1) Real focus only exists on one plane. That plane has no depth dimension. Focus then is one plane thick, of no dimension.
2) Everything else is just varying degrees of blurriness.
3) The degree of blurriness is dependent upon the distance from the focus plane and the circles produced on the film or sensor.
4) Larger circles means further distance and more blur.
5) The circles can be so small they appear to be points.
6) Small circles appear in focus.
7) Small circles can become large circles when enlarged, and this become blurry. They are no longer small enough to be confused as points on an enlargement.


Question is does point 7 remain true if viewing distance changes proportionately to the enlargement?

I suppose that is the root of discussion, Either the comparative assessment of DOF is made at a constant defined distance and size of print eg 8x10 arms length away.
Or the comparative assessment is made at a distance proportional to the enlargement size of the print.

But comparing different sized prints at arms length is less revealing.