Is it .27 or .30 when figuring out a focal length - Which one do you use?

[Ig Nacio]

Hi,

When I see a LF focal length, I usually multiply
that focal length by .30 in order to get its
equivalent in 35mm.

For example, a LF lens with a 150mm focal length
will be multiplied by the .30 factor to get the 35mm.
equivalent, that is 45mm.

However, I was reading a conversation on the
internet and a guy mentioned that it is not .30
the right factor to multiply by, but .27.

That would give a LF lens of 150mm. a focal length
of 40.5mm.

Which of the two factors is right? Which one have
you be using?

Thank you, kind regards!

[Gary Beasley]

That would depend on whether you are using the vertical or horizontal measure to compare by. 35mm is closer in aspect ratio to 5x7, 4x5 ratio would be clipping the sides. However I think the .27 may be close as a 150 is just slightly wide.

[Dan Fromm]

Nacho, whatever you do will be wrong. Welcome to the club.

[Two23]

Not wanting to have a headache I just multiply the 35mm x3, or divide by 3. Since I shoot 4x5, 5x7, 8x10 I've quite trying to think in terms of numbers anyway. I have a wide lens, a normal lens, and a portrait lens.


Kent in SD

[Mark Sawyer]

A six-inch lens on a 4x5 is equivalent to a 150mm lens on a 4x5.

Best not to think in terms of equivalents and just let large format be its own thing. Asking "what lens would I use on a 35mm?" to figure out what lens to use on a 4x5 is like deciding where to take your girlfriend for Valentine's Day dinner based on your ex-girlfriend's favorite restaurant...

[ic-racer]

...a guy mentioned...
He would need to know how much of your 35mm negative you print and the diagonal of your 35mm camera's film gate to give correct advice.

[Joseph Kashi]

I shoot multiple formats, including 4x5, 5x7, Micro 4/3 (gasp ! ) and full-frame. The varying aspect ratios of these several formats make a single angle of view ( usually the diagonal) multiplier not very useful, at least for me. Trying to compare the normal diagonal field of view across several formats with different aspect ratios, such as 4x5 to 35mm equivalent, is apples and oranges.

So, I personally calculate the equivalence for my own use by comparing the long axis of different formats so that there's an equivalent horizontal angle of view that's actually equivalent and comparable. The same can be done using the short axis if that's your taste.

35mm full-frame has a 36mm long axis while the image area of the long axis of 4x5 is roughly 120mm and 5x7's long axis image area is roughly 172 mm. I know that the image area of sheet film is slightly different but a percent or two difference is basically irrelevant to a focal length equivalence calculation - if those few percent are important in a particular circumstance, then just use the practical approach of checking the ground glass edges for certainty.

Dividing 36mm/120mm = .3 long-axis multiplier going from 35mm to 4x5, or a long-axis divisor going from 4x5 to 35mm of roughly 3.3

For 5x7, it's very nearly the 35mm aspect ratio, so it's a bit more intuitive. 36mm divided by 172mm is just about a .21 multiplier or a focal length divisor of roughly 4.8

A 150mm lens on 4x5 thus gives a 35mm long axis equivalent of roughly a 45mm lens, whether you use a multiplier or a divisor.

A 43mm lens on 35mm is its "normal" lens as classically defined using the diagonal angle of view calculation.

So, 150mm is pretty close to classic normal on 4x5 whether calculating by the long axis method or the diagonal angle of view approach.

[abruzzi]

When you first learn a foriegn language, you are translating what you hear in your head to your native language, after you get better and do it long enough you learn to think in that language (to an extent.) Focal lengths is kind of the same thing. When you start in a new format you have to translate to a format you know, but after a while, you don't translate 135mm, you just know what it will look like (approximately) in the format you're shooting.

For some reason the 35mm focal lengths have become so ingrained that it is even a standard entry in digital camera EXIF data--"FocalLengthIn35mmFormat". So my reccomendation is not to get too hung up on the specifics--when you're just moving to the format, use the multiply/divide by 3 rule. Its not really accurate but it give you a ballpark number. Then learn to think in the new focal lengths.

[lassethomas]

I'm using 3.5 as the devisor which is approximately equal to 0.29.
But since the ratios are different there is no right or wrong.
Don't waste to much time...

And then try to equivalent 4x10 to 35mm :)

[maltfalc]

multiply or divide by 3.5 for 4x5 and 35mm. that's 4x5 with the rails cropped out and based on equivalent normal lenses (152mm and 43mm).

[Graham Patterson]

And eventually one notices that numbers like 90, 210, or 300 crop up often - because they are the 'standard' for some format or another. If you are into numerology it will mess with your head 8-)

After a lot of years I pretty much know where I need to stand to use a particular lens on the format I am using. I am waiting for the time when the 35mm equivalent goes away because consumer digital cameras are split between full frame 35mm and 4/3 format, and the majority of consumer use is probably a phone using a sensor about the size of a baby's finger nail. I guess I'm feeling old and grumpy tonight.

[xkaes]

For me, it depends on what the format of the final print will be -- and I don't mean the size of the paper. No matter what size film I am using, the actual final print might be anything from square to panorama (horizontal OR vertical. And much of the time, I have no idea what that will be when I take the picture. Just one of the many problems of living in canyon country.

For 4x5" lenses, I usually start out by dividing the focal length by 4 -- pretty easy. That gets me in the ballpark, but after seeing the subject on the ground glass, I often end up with a different lens -- sometimes wider, sometimes shorter.

I have a 2x2.5" cut-out in an 8x10" gray card that I use the compose the scene first. The distance between the card and my eye tells me what lens to start with. I have a tape-ruler connecting my mouth and the card.

[Alan Klein]

I shoot multiple formats, including 4x5, 5x7, Micro 4/3 (gasp ! ) and full-frame. The varying aspect ratios of these several formats make a single angle of view ( usually the diagonal) multiplier not very useful, at least for me. Trying to compare the normal diagonal field of view across several formats with different aspect ratios, such as 4x5 to 35mm equivalent, is apples and oranges.

So, I personally calculate the equivalence for my own use by comparing the long axis of different formats so that there's an equivalent horizontal angle of view that's actually equivalent and comparable. The same can be done using the short axis if that's your taste.

35mm full-frame has a 36mm long axis while the image area of the long axis of 4x5 is roughly 120mm and 5x7's long axis image area is roughly 172 mm. I know that the image area of sheet film is slightly different but a percent or two difference is basically irrelevant to a focal length equivalence calculation - if those few percent are important in a particular circumstance, then just use the practical approach of checking the ground glass edges for certainty.

Dividing 36mm/120mm = .3 long-axis multiplier going from 35mm to 4x5, or a long-axis divisor going from 4x5 to 35mm of roughly 3.3

For 5x7, it's very nearly the 35mm aspect ratio, so it's a bit more intuitive. 36mm divided by 172mm is just about a .21 multiplier or a focal length divisor of roughly 4.8

A 150mm lens on 4x5 thus gives a 35mm long axis equivalent of roughly a 45mm lens, whether you use a multiplier or a divisor.

A 43mm lens on 35mm is its "normal" lens as classically defined using the diagonal angle of view calculation.

So, 150mm is pretty close to classic normal on 4x5 whether calculating by the long axis method or the diagonal angle of view approach.

That's how I look at it. What is the horizontal angle of view, not the oblique view since you're dealing with different formats. If you use this app below, you will see that a 150mm lens of a 4x5 has an angle of view of 45.9 degrees. Full frame equivalent of 43mm lens in full format would give you 45.4 degree horizontally. So your 3.3 divisor is good. Probably closer to 3.5.
https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{%22c%22:[{%22f%22:19,%22av%22:%2216%22,%22fl%22:150,%22d%22:30480,%22cm%22:%220%22}],%22m%22:0}

[Alan Klein]

For me, it depends on what the format of the final print will be -- and I don't mean the size of the paper. No matter what size film I am using, the actual final print might be anything from square to panorama (horizontal OR vertical. And much of the time, I have no idea what that will be when I take the picture. Just one of the many problems of living in canyon country.

For 4x5" lenses, I usually start out by dividing the focal length by 4 -- pretty easy. That gets me in the ballpark, but after seeing the subject on the ground glass, I often end up with a different lens -- sometimes wider, sometimes shorter.

I have a 2x2.5" cut-out in an 8x10" gray card that I use the compose the scene first. The distance between the card and my eye tells me what lens to start with. I have a tape-ruler connecting my mouth and the card.

I have one of those F64 viewfinders with the special BW filter for previewing scenes. Stopped using it. Now I use my micro 4/3 digital camera with a zoom lens to scout out the picture location, crop, and lens I need to shoot 4x5. I've already measured out the zoom setting on the digital to measure up against the angle of view for the 4x5 lenses I have. So I know immediately, which 4x5 lens matches the view I want and where to set up the tripod. (I drop something on the ground where I'm standing.) Another advantage is I can switch the digital to BW from color when shooting BW film to "see" the picture in BW. I also use the digital as a light meter, but that's another story.

[jnantz]

I gave up searching for and striving perfection decades ago I just multiply or divide by three,
being off by a few millimeters I don't think matters much.
of course it might matter to someone else, LF and photography in general seems to attract people
who obsess about minute details instead of making photographs .. to each their own.

[Joseph Kashi]

I have one of those F64 viewfinders with the special BW filter for previewing scenes. Stopped using it. Now I use my micro 4/3 digital camera with a zoom lens to scout out the picture location, crop, and lens I need to shoot 4x5. I've already measured out the zoom setting on the digital to measure up against the angle of view for the 4x5 lenses I have. So I know immediately, which 4x5 lens matches the view I want and where to set up the tripod. (I drop something on the ground where I'm standing.) Another advantage is I can switch the digital to BW from color when shooting BW film to "see" the picture in BW. I also use the digital as a light meter, but that's another story.

Hi, Allen - I agree, and do much the same with my M4/3 Pen-F and there's the further advantage of having a good-quality digital RAW image as a backup. It also can give very precise spot-metering to check against the hand-held meter reading. I seem to recall that Dr. Luong, this site's founder, does similarly.

[EBJohnson]

I divide my 4x5 lens by 3.75... That gets me to a place where things "feel" right, regardless of the exact comparison... So my 150 is just wider than "Normal", my 65 feels pretty dang close to a 17mm ultra wide... and my 210 is out in the weeds as a focal length that's not really comparable to anything I've shot with at 55ish... not quite "normal" not quite like my Nikkor Micro 60/2.8... and then my Graflex 162 squeaks in at JUST wider than I expect at a "truer normal" (based on the diagonal). I've been looking at a 180, which should feel pretty dang close to a 50mm (135 format), just haven't found the one I want to pay for yet...

[Tobias Key]

I don't think it's worth obsessing about really. Most people would agree that 150mm is the defacto 'standard' lens for 4x5 90mm is the most commonly used wide, and 210mm the favourite portrait lens. 90mm is the widest you can go without losing a lot of movements and will work with most cameras (75mm often needs a recessed board). 210mm is as long as you can go while retaining a copal 1 shutter, copal 3's having a low top shutter speed and adding a lot of weight/bulk. These types of considerations are very important in large format, probably more important than finding an equivalent to some arbitrary 35mm focal length.

[EBJohnson]

Unless you are accustomed to working with 35mm to the point where you want to have a reference for eyeballing, which was the point for me... For instance when I first shot with the 162mm that came on the Crown Graphic I had, I knew that 150 was the 4x5 "standard, so I expected the 162 to be a touch longer than normal... So I set up in a spot that I'd shot a scene before with a 60mm, and was shocked to see that it was wider, much wider, than I expected to see... I was still able to take a decent shot and there are other issues at hand such a different aspect ratio, but still... and now when I shoot with a 150, I think in advance that it's going to be closer to a 35 than a 50... and I have a better time setting up in the right spot... It's especially helpful when you consider with a 35 you can walk around until you find the "right spot" to take a shot, but with 4x5 you need to set up a bit every time so the walking around part of that situation has a lot more to it...

All that said, it's not a practice that I expect to maintain as I get more accostomed to the 4x5 format, but it has been helpful at the onset of the process of learning the format.

[maltfalc]

I divide my 4x5 lens by 3.75... That gets me to a place where things "feel" right, regardless of the exact comparison... So my 150 is just wider than "Normal", my 65 feels pretty dang close to a 17mm ultra wide... and my 210 is out in the weeds as a focal length that's not really comparable to anything I've shot with at 55ish... not quite "normal" not quite like my Nikkor Micro 60/2.8... and then my Graflex 162 squeaks in at JUST wider than I expect at a "truer normal" (based on the diagonal). I've been looking at a 180, which should feel pretty dang close to a 50mm (135 format), just haven't found the one I want to pay for yet...

Unless you are accustomed to working with 35mm to the point where you want to have a reference for eyeballing, which was the point for me... For instance when I first shot with the 162mm that came on the Crown Graphic I had, I knew that 150 was the 4x5 "standard, so I expected the 162 to be a touch longer than normal... So I set up in a spot that I'd shot a scene before with a 60mm, and was shocked to see that it was wider, much wider, than I expected to see... I was still able to take a decent shot and there are other issues at hand such a different aspect ratio, but still... and now when I shoot with a 150, I think in advance that it's going to be closer to a 35 than a 50... and I have a better time setting up in the right spot... It's especially helpful when you consider with a 35 you can walk around until you find the "right spot" to take a shot, but with 4x5 you need to set up a bit every time so the walking around part of that situation has a lot more to it...

All that said, it's not a practice that I expect to maintain as I get more accostomed to the 4x5 format, but it has been helpful at the onset of the process of learning the format.sounds like your issue is that you think 50mm is the normal lens for 35mm film. it's not, 43mm is. 152mm=43mm, 175mm=50mm.

[jnantz]

sounds like your issue is that you think 50mm is the normal lens for 35mm film. it's not, 43mm is. 152mm=43mm, 175mm=50mm.


hi maltfalc

sorry to be a contrarian or seemingly problematic but while some folks go by the diagonal measurement to determine the "normal" lens, others just suggest whatever lens they use "normally" to give them the look they want. I have an uncle ( really he's my 2nd cousin once removed ) who did professional photography ( catalog work ) and his "normal" was something like a 210 shorter than that was too wide longer than that too narrow. maybe that's what's going on with EB ... ?

[maltfalc]

hi maltfalc

sorry to be a contrarian or seemingly problematic but while some folks go by the diagonal measurement to determine the "normal" lens, others just suggest whatever lens they use "normally" to give them the look they want. I have an uncle ( really he's my 2nd cousin once removed ) who did professional photography ( catalog work ) and his "normal" was something like a 210 shorter than that was too wide longer than that too narrow. maybe that's what's going on with EB ... ? we're talking about equivalent focal lengths here. it's super common for people to mistakenly think 50mm is the normal for 35mm film. he specifically mentions normal lenses based on diagonals, the 4x5 normal lens being 150mm and being surprised that a 150mm lens looks wider than 50mm and that a 162mm lens doesn't look a touch longer than "normal"...

[EBJohnson]

sounds like your issue is that you think 50mm is the normal lens for 35mm film. it's not, 43mm is. 152mm=43mm, 175mm=50mm.

In fairness, I'm falling victim to the thing I'm calling out in the 150mm as "normal" argument for 4x5 and working off of those assumptions because that is what I've shot for over 20yrs... either way, per the numbers both "normals" are wrong, but are still used as.

Regardless, when I mount my 150 on my 4x5 it "feels" more like a 35mm than a 50mm... though it is closer to 40mm (per my arithmetic and judgement).

[Bernice Loui]

35mm being a 3:2 image ratio and 4x5 or 8x10 being a 5:4 image ratio does not direct translate to what is defined as a "normal lens".

Normal lens being defined as size of objects front to rear of the image perceived. Lens choice should be decided on image perspective then focal length needed to achieve this perspective in the print/image.

Typical "normal lens" for 4x5 would be 150mm to 210mm. Typical "normal lens" for 35mm still film would be 40mm to 60mm, but the aspect ratios are different.

Normal lens example, 40mm full frame digital (35mm, 3:2 aspect ratio), aprox diagonal Angle of view 57º. Note size of items in this image.
224840

224841

Wide angle lens example, 14mm full frame digital (35mm, 3:2 aspect ratio), aprox diagonal Angle of View 114°. Note size of items in this image (expansion).
224842

Tele lens example, 300mm full frame digital (35mm, 3:2 aspect ratio), diagonal Angle of View aprox 8°. Note size of items in this image (compression).
224844


Lens focal length should be driven by image perspective/size of objects "front to back" relative to how the "human eye" might see them in real time. Absolute focal length is not as important as lens/camera placement (height, distance to subject and LOTs more) which has a HUGE effect on the image being made.


Bernice

[Alan Klein]

If you're using a zoom lens, you wouldn't concern yourself with wide, normal or tele but what framing looks best. Then pick the lens that it works best with.

[Bernice Loui]

Zoom lenses can develop un-healthy habits due to their "lazy_ness" factor. Focal length alone should NOT be used framing-composition-perspective and what is and is not in focus, it is more a combo of lens/camera position + lens focal length + image recording lens aperture.

The overly common zoom lens on digital and 35mm film and lesser degree 120 roll film tends to develop the habit of being in one position then "zooming" as needed to "frame" the image. What should be done is know what the image needs to be, then figuring out lens/camera position + the lens focal length needed to achieve what was in mind. This begins to dip into personality types and how any given individual works the image making process. Essentially, not everyone can or have the ability to pre-visualize the image then apply the tools needed to make the image in mind.


Tends to favor fixed focal length lenses over zooms for digital and roll film cameras.
Bernice




If you're using a zoom lens, you wouldn't concern yourself with wide, normal or tele but what framing looks best. Then pick the lens that it works best with.

[EBJohnson]

If you're using a zoom lens, you wouldn't concern yourself with wide, normal or tele but what framing looks best. Then pick the lens that it works best with.

I mean... when I do use a Zoom lens, I 100% choose the lens based on where it's range falls within those guidelines...

[Oren Grad]

I learned from experience that the focal length that corresponds most closely to the way I see, and which serves best as a standard lens for me, is whatever I can get that's closest to 7/8 of the format diagonal. The exception is panoramic formats beyond a 3:2 aspect ratio, where I'm more comfortable with a focal length about 3/2 times the vertical dimension of the format. Operational definitions of "long" and "short" follow from that.

Of course, this isn't a universal rule. The point is to let your own pictures tell you what is right for you - pay attention to how you see and how your pictures come out.

[jnantz]

we're talking about equivalent focal lengths here. it's super common for people to mistakenly think 50mm is the normal for 35mm film. he specifically mentions normal lenses based on diagonals, the 4x5 normal lens being 150mm and being surprised that a 150mm lens looks wider than 50mm and that a 162mm lens doesn't look a touch longer than "normal"...

thanks !

like I said photography attracts all types of people. ... personally I don't even think I'd notice the difference between a 15O and 162 mm lens. but that's just me I'm oblivious... and im more interested in other things...

that said, good luck OP, EB and whoever else might be distressed
gotta do what makes you happy!
John

[maltfalc]

35mm being a 3:2 image ratio and 4x5 or 8x10 being a 5:4 image ratio does not direct translate to what is defined as a "normal lens".

Normal lens being defined as size of objects front to rear of the image perceived. Lens choice should be decided on image perspective then focal length needed to achieve this perspective in the print/image.

Typical "normal lens" for 4x5 would be 150mm to 210mm. Typical "normal lens" for 35mm still film would be 40mm to 60mm, but the aspect ratios are different.

Normal lens example, 40mm full frame digital (35mm, 3:2 aspect ratio), aprox diagonal Angle of view 57º. Note size of items in this image.
224840

224841

Wide angle lens example, 14mm full frame digital (35mm, 3:2 aspect ratio), aprox diagonal Angle of View 114°. Note size of items in this image (expansion).
224842

Tele lens example, 300mm full frame digital (35mm, 3:2 aspect ratio), diagonal Angle of View aprox 8°. Note size of items in this image (compression).
224844


Lens focal length should be driven by image perspective/size of objects "front to back" relative to how the "human eye" might see them in real time. Absolute focal length is not as important as lens/camera placement (height, distance to subject and LOTs more) which has a HUGE effect on the image being made.


Bernice

"normal" focal length equals image diagonal, regardless of ratio, period. that's what a normal lens is, that's what the term means. 152mm for 4x5 with a modern holder, give or take a mm depending on film holder variations. 43mm for standard 35mm cameras. crop factor is also based on diagonals, at least according to every camera manufacturer on earth.

[Alan Klein]

I remember reading somewhere that normal lens is the diagonal length of the sensor or film size. So in the case of a 24mm by 36mm full format, that's equal to around 43mm. In the case of a 4" by 5" that would be 6.4" or 163mm . Other definition for normal is just what you think is normal to you.

[xkaes]

In the case of a 4" by 5" that would be 6.4" or 163mm .

4x5" film is 4x5" -- but not the image size, due to the film holder. Large format, and medium format film always has image sizes smaller than the film size -- so does "35mm", which really isn't 35mm. With 35mm we get it right by using the image size, and we need to do the same with all other formats.

[abruzzi]

4x5" film is 4x5" -- but not the image size, due to the film holder. Large format, and medium format film always has image sizes smaller than the film size -- so does "35mm", which really isn't 35mm. With 35mm we get it right by using the image size, and we need to do the same with all other formats.

35mm actually doesn't refer to the image size at all but the entire width of the film, including the sprocket holes--technically 34.974mm, but yeah all the sizes out there are nominal and the actual size is different (and frequently varies from once device to the next).

As for the definition of "normal" I'd point out that the diagonal is technically a secondary characteristic, not the definition of normal. Normal is usually defined as as a lens that gives a view on a particular format that approximates the field of view of human vision. That can be approximated using the diagonal, but the definition itself is more subjective than objective. The reality is our vision is actually close to a fisheye lens, but the way we see is very very different than a camera and film because we have focus on what is in front of us with very little attention to the periphery, but since that focus/periphery is perceptual, there is some range of what might be considered "normal." For me, a 50mm on 135 is close, but I find a 60mm is closer to my normal angle of focus.

[drew.saunders]

I guess I'm old enough to remember how to do math with fractions, so I compare along the approximate diagonal (43.3mm vs 154mm) by multiplying by 2/7 or 7/2, depending on which direction I'm converting. Yes, I have a calculator app on the phone in my pocket, but I like to keep my remaining brain cells (thanks chemo brain!) functioning well by doing mental math.

[Bernice Loui]

Absolute lens focal length of what is considered theoretically en all "normal" is FAR less significant than how any lens is used. Lens focal length marked on any lens is completely never precisely as marked due to production tolerances and variations. These variations are often small, point being there is zero to be gained by focusing on irrelevant minutiae.

Adding to this "normal lens issue" humanoids have two eyes resulting in stereo vision with depth perception (and a LOT "wider field of view than a "normal lens) that can translate to relative distance. Ya take this innate way of humanoid ways of vision then flatten it to a 2D or non stereoscopic rendering. Now, how does a 2D begin to try conveying or try fooling human vision into believing this flat 2D image has spatial content in the ways humanoid vision sees or views in essentially 3D _?_


Bernice

[Ig Nacio]

Hi,

Thank you for all your messages : )!!!

Very kind regards!

[pdmoylan]

Alan is right on this, the diagonal of 35mm is 43mm while 4x5 is 163mm, so factor 43/163 = .263. I extracted from this that for every 4mm of 35mm format, you get 15mm in the 4x5 format. Taking this further, a 150mm in 4x5 is 40mm in 35mm format, 120mm = 32mm, 90mm =24mm, 75mm is 21mm in 35mm format.


However, if you shave off 6mm on the long side of 35mm format to get 24x30 to maintain the same aspect ratio as 4x5, the modified format has a diagonal of 38.4mm vs 43mm as above. 0.236 is the resulting factor.

Not sure where .30 comes from though some have discussed the usable portion of 4x5 film being less, perhaps this is the source.

The purpose of all of this is to approximate the angle of view between the formats. One frequently defaults to the 150mm as it is among the least expensive, lightest etc, but who uses 40mm in 35mm format?

Seems to me that the AOV you favor in 35mm is a starting point for choosing LF focal lengths. Given my penchant for 24-28mm lenses in 35mm format, lenses in the 90mm-110mm range would be desirable.

On the other hand I found the 210mm unnatural AOV; yet, with movements, it opened up doors that forced me to change perspective. Keep an open mind, particularly in using longer lenses for closeups and intimate landscapes.

One can say, "love the one your with". Meaning choose reasonably and learn to see with the associated AOV with movements.

[maltfalc]

Alan is right on this, the diagonal of 35mm is 43mm while 4x5 is 163mm, so factor 43/163 = .263. I extracted from this that for every 4mm of 35mm format, you get 15mm in the 4x5 format. Taking this further, a 150mm in 4x5 is 40mm in 35mm format, 120mm = 32mm, 90mm =24mm, 75mm is 21mm in 35mm format.


However, if you shave off 6mm on the long side of 35mm format to get 24x30 to maintain the same aspect ratio as 4x5, the modified format has a diagonal of 38.4mm vs 43mm as above. 0.236 is the resulting factor.

Not sure where .30 comes from though some have discussed the usable portion of 4x5 film being less, perhaps this is the source.

The purpose of all of this is to approximate the angle of view between the formats. One frequently defaults to the 150mm as it is among the least expensive, lightest etc, but who uses 40mm in 35mm format?

Seems to me that the AOV you favor in 35mm is a starting point for choosing LF focal lengths. Given my penchant for 24-28mm lenses in 35mm format, lenses in the 90mm-110mm range would be desirable.

On the other hand I found the 210mm unnatural AOV; yet, with movements, it opened up doors that forced me to change perspective. Keep an open mind, particularly in using longer lenses for closeups and intimate landscapes.

One can say, "love the one your with". Meaning choose reasonably and learn to see with the associated AOV with movements.

the IMAGE diagonal of 4x5 is 152mm/6", not 163mm. crop factor is 3.5 or 0.28. 150mm=43mm, 120mm=34mm, 90mm=26mm, 75mm=21mm.

[pdmoylan]

4x5 diagonal in millimeters is 163mm

4 inches = 101.6 MM
5 inches = 127mm

to obtain diagonal calculate using pythagorean theorum. a squared = 10,302.56, b squared = 16,129. Addition = 26,451.50. Square root of sum is 163mm.

[maltfalc]

4x5 diagonal in millimeters is 163mm

4 inches = 101.6 MM
5 inches = 127mm

to obtain diagonal calculate using pythagorean theorum. a squared = 10,302.56, b squared = 16,129. Addition = 26,451.50. Square root of sum is 163mm.

IMAGE diagonal is what matters. IMAGE. the edges of the film that are hidden by the film holder don't matter, just like the perforated edges of 35mm film or the outer edges of a sensor don't matter. it's 152mm. go get a film holder or negative and measure it yourself, ffs. literally every camera manufacturer in the world measures the diagonal and determines crop factor this way.

[Alan Klein]

Just an aside. I shoot an RB67 which uses 120 roll film and shoots 6x7cm. However, since the back rotates so you can shoot either portrait or landscape mode without the need of turning the camera 90 degrees, the lens has to handle an image that's at least 7x7cm. So I don't know how that fits into our discussion.

[pdmoylan]

So you know all of the scientists at each camera manufacturer and how they perform calculations. Impressive.

This comes across as trolling as I already mentioned above that others may choose an alternate factor based upon usable image. You also did not respond to my suggestion that perhaps one should be considering the same aspect ratio to determine the “proper” factor.

In the end quell difference? Will it make you a better image maker if you choose one over another?

Many years of dealing with those who insist they are right to win an argument, all I can say is there is never any justice realized in being “right” on any subject.

And for anyone obsessed with winning an argument I would direct to the last debate between Gore Vidal and William F. Buckley. It’s interesting that even the most seemingly refined of individuals will resort to epithets when he finds he is unable to leverage an advantage in the debate. No justice.

[maltfalc]

So you know all of the scientists at each camera manufacturer and how they perform calculations. Impressive.

This comes across as trolling as I already mentioned above that others may choose an alternate factor based upon usable image. You also did not respond to my suggestion that perhaps one should be considering the same aspect ratio to determine the “proper” factor.

In the end quell difference? Will it make you a better image maker if you choose one over another?

Many years of dealing with those who insist they are right to win an argument, all I can say is there is never any justice realized in being “right” on any subject.

And for anyone obsessed with winning an argument I would direct to the last debate between Gore Vidal and William F. Buckley. It’s interesting that even the most seemingly refined of individuals will resort to epithets when he finds he is unable to leverage an advantage in the debate. No justice. it's a universal, industry standard measurement. NOBODY includes the edges of the film when measuring a format's dimensions. it's literally the exact same method used to calculate the 43mm diagonal for 35mm film, WHICH YOU ACCEPT. i'm done wasting my time on someone who can't have an honest conversation. welcome to my ignore list.

[jnantz]

wow, I never knew calculating and knowing the so called "normal" lens size actually mattered in the grande scheme of things. one would think if it really was so important every lens manufacturer going back to 1839 ( or before that if you count the obscures people used to draw with ) would have sold (or would still sell) a LF lens that is "normal" focal length and regarding smaller format cameras, same thing one if it really mattered the companies would have made it a priority to sell that focal length lens. obviously I have been wasting my time thinking about other things .

[ic-racer]

Just an aside. I shoot an RB67 which uses 120 roll film and shoots 6x7cm. However, since the back rotates so you can shoot either portrait or landscape mode without the need of turning the camera 90 degrees, the lens has to handle an image that's at least 7x7cm. So I don't know how that fits into our discussion.
I know you know the answer here. No the lenses only need to cover 6x7, think about it.

[Alan Klein]

I know you know the answer here. No the lenses only need to cover 6x7, think about it.

You're right for 6x7. What confused me is that the RB67 lens has an image circle that covers larger than 6x7 because there are film backs for 6x8 and I believe 6x9. So the lens focal length shouldn't follow the formula used normally. Maybe someone else has a better description of what's going on with the RB67 lenses.

[neil poulsen]

In doing these kinds of calculations, I like to take into account aspect ratio.

So in finding a 4x5 focal length equivalent in 35mm, I would assume that I would be framing the same image on a 35mm camera with a 4x5 aspect ratio. So, I would multiply the focal length of the 4x5 lens by 25% to obtain it's 35mm equivalent.

In finding a 35mm focal length equivalent in 4x5, I would assume that I would be framing the same image on a 4x5 camera with a 2/3 aspect ratio. So, I would multiply the focal length of the 35mm lens by 3.4 to obtain its 4x5 equivalent.

Sometimes the ratio of the diagonals is used as an approximation. The ratio of a 35mm diagonal to a 4x5 diagonal is 27.8%

These conversions are based on actual image dimensions that I measured using a caliper on a 35mm camera, and on a 4x5 sheet film holder. These vary I imagine from company to company. But, the above conversions are probably accurate enough.

[r.e.]

I figure that these conversions, which do indeed differ depending on approach, are just rough approximations. As a practical matter, I sidestep the whole question and use a Director's Viewfinder; in particular, Artist's Viewfinder (https://www.artistsviewfinder.com). Saves me a lot of time.

Artist's Viewfinder is one of the apps discussed in the thread What Scouting/Planning Apps Are You Using in 2021? (https://www.largeformatphotography.info/forum/showthread.php?164815-What-Scouting-Planning-Apps-Are-You-Using-in-2021)

Screen Capture, Artist's Viewfinder

225095

[Alan Klein]

I figure that these conversions, which do indeed differ depending on approach, are just rough approximations. As a practical matter, I sidestep the whole question and use a Director's Viewfinder; in particular, Artist's Viewfinder (https://www.artistsviewfinder.com). Saves me a lot of time.

Artist's Viewfinder is one of the apps discussed in the thread What Scouting/Planning Apps Are You Using in 2021? (https://www.largeformatphotography.info/forum/showthread.php?164815-What-Scouting-Planning-Apps-Are-You-Using-in-2021)

Screen Capture, Artist's Viewfinder

225095

I use my micro 4/3 camera as a Director's Viewfinder with its 4:3 aspect ratio to determine the shot and lens on my 4x5 camera. 4:3 is the same as 20:15 and 5:4 is the same as 20:16. So it's very close, only off 1/20th on the vertical.

[ic-racer]

Just a comment out of curiosity that people use the 35mm frame as a reference, seeing as so few 35mm cameras are being made or sold these days. Even more curious as 40-45mm lenses are so uncommon in that format. I believe there are many more 4x5 camera manufacturers than 35mm cameras today.
In fact I frequently need to go the other way. For example, find which lens on my 6x9cm camera, shooting Instax format, would be closest to my 90mm/4x5in.

[r.e.]

Just a comment out of curiosity that people use the 35mm frame as a reference, seeing as so few 35mm cameras are being made or sold these days. Even more curious as 40-45mm lenses are so uncommon in that format. I believe there are many more 4x5 camera manufacturers than 35mm cameras today.
In fact I frequently need to go the other way. For example, find which lens on my 6x9cm camera, shooting Instax format, would be closest to my 90mm/4x5in.

There's a decent market for full frame 35mm digital. Users of cameras with smaller sensors all use a crop factor, and work out calculations, based on full frame 35mm. I think that it's still the standard reference in the digital world.