DOF on 8x10 vs. 4x5?

[LFLarry]

I am trying to better understand the reasons why there is less depth of field (DOF) with 8x10 vs. 4x5 at the same aperture.

I think I understand the basic principles of light and that larger film at the same aperture as a smaller format like 4x5 has less DOF.

Can someone help me better understand the "why" and the science behind this a little better?

Thanks

[Dan Fromm]

Short answer, if the image size on 8x10 is the same size relative to the format's size as on 4x5 it will be twice as big. Magnification will 8x10 will be twice magnification on 4x5. Since DoF is controlled by, and only by, magnification and relative aperture (f/stop) at the same magnification and f/stop 8x10 will have less DoF than 4x5. 4x5 will have less DoF than 24x36. And so on.

[LFLarry]

Makes total sense Dan. Thank you.


Short answer, if the image size on 8x10 is the same size relative to the format's size as on 4x5 it will be twice as big. Magnification will 8x10 will be twice magnification on 4x5. Since DoF is controlled by, and only by, magnification and relative aperture (f/stop) at the same magnification and f/stop 8x10 will have less DoF than 4x5. 4x5 will have less DoF than 24x36. And so on.

[Eric Woodbury]

It's all very confusing. Thing to remember is longer lenses reduce apparent DOF and there is no winning.

Same f/# and same lens gives same DOF. Lens doesn't know how big your image is. However, if you compare "normal" lens for different formats, this will change the circumstances.

DOF approximately equals

2 * (D ^ 2) * N * c /(f^2),

where D is subject distance, N is f/#, c is chosen circle of confusion diameter, and f is focal length. [I know, I'm not fond of the math either.] This shows what changes DOF. If you hold the focal length constant, the f/# constant, the confusion constant, and the distance to subject constant, then DOF doesn't change. If you switch from 4x5 to 8x10 AND twice the lens, then you can see that there is a change. Change just the lens by twice and DOF changes by 4X since focal length (on the bottom) is squared. Chances are you'd change your distance twice, too, and it is squared on top, cancelling the focal change. However, with a longer lens, there is "compression", that means a given distance looks shorter, but measured it's the same.

(Usually with 8x10, it is assumed that the enlargement is less, too, and that the circle of confusion need not be so small.)

[Eric Woodbury]

Yeah, what he said.

[William Whitaker]

Format does not affect depth of field.

[Jim Jones]

When the same images captured on various formats are presented at the same size, the only factor that affects DOF is the diameter of the lens aperture. That is the most practical explanation I know. It also leads to a simple way of determining the hyperfocal distance, which is typically 2000 times the aperture diameter as seen through the front of the lens, regardless of the focal length or the camera format. However, that figure of 2000 can vary widely, depending on the degree to which the image is enlarged and the preferences of the photographer.

[LFLarry]

Eric, this is very helpful and interesting. Thank you for sharing this.

This all opens up another question that I have recently started thinking about.

Long story short, because of health reasons, I am not able to get out and do landscapes with my 4x5 right now so I have been looking at options to keep me photographing. So I decided to explore doing still life in a little make-shift studio in a spare bedroom. This is a new area for me and I quickly have realized that I need to get my mind around reproduction ratios, exposure compensation based on bellows extension, and depth of field.

I am just starting to think about this, but maybe you already know this off the top of your head.

I was thinking for any given exposure, that I need to follow a process or a checklist. This is just how my mind works.

Do you have any recommendations on an approach? For example, let's say that I am photographing some donuts using my 240mm lens and it turns out that I am using 260mm of bellows extension. And just to be clear, do I measure from front standard to rear standard to determine this or do I have this wrong?

I would like an easy way to document the magnification/reproduction ratio for the exposure and determine how much exposure compensation I need based on my bellows extension.

Based on what I have read in a variety of large format textbooks, most tend to indicate that I probably don't want to use an aperture greater than f/16 or so as a general rule.

Possibly I am forgetting something else?

Hopefully, I am explaining this correctly and it makes sense.

Any insights on doing the "math" correctly would be appreciated.

-Larry




It's all very confusing. Thing to remember is longer lenses reduce apparent DOF and there is no winning.

Same f/# and same lens gives same DOF. Lens doesn't know how big your image is. However, if you compare "normal" lens for different formats, this will change the circumstances.

DOF approximately equals

2 * (D ^ 2) * N * c /(f^2),

where D is subject distance, N is f/#, c is chosen circle of confusion diameter, and f is focal length. [I know, I'm not fond of the math either.] This shows what changes DOF. If you hold the focal length constant, the f/# constant, the confusion constant, and the distance to subject constant, then DOF doesn't change. If you switch from 4x5 to 8x10 AND twice the lens, then you can see that there is a change. Change just the lens by twice and DOF changes by 4X since focal length (on the bottom) is squared. Chances are you'd change your distance twice, too, and it is squared on top, cancelling the focal change. However, with a longer lens, there is "compression", that means a given distance looks shorter, but measured it's the same.

(Usually with 8x10, it is assumed that the enlargement is less, too, and that the circle of confusion need not be so small.)

[Jody_S]

It's pretty easy to understand that if you take an image with a 240mm lens at f22 on your 4x5, then mount the lens on your 8x10 and re-take the image still at f22, the resulting images will have the same depth of field.


If, on the other hand, you use a 'normal' 135mm lens at f22 on your 4x5, and compare the image to one taken with a 'normal' 300mm lens at f22 on your 8x10, the depth of field will differ.

[LFLarry]

Very interesting Jim. I was reading in the Simmons "Using the View Camera" book today, and I think he mentions a value of 1500 vs. 2000, but I could be remembering that wrong? Do you think hyperfocal is useful or relevant when doing product/studio work? I am just starting to explore photographing small objects in my little makeshift studio which range from less than 1:1 up to 1:1 and I have been thinking more about depth of field and how to best manage it.


When the same images captured on various formats are presented at the same size, the only factor that affects DOF is the diameter of the lens aperture. That is the most practical explanation I know. It also leads to a simple way of determining the hyperfocal distance, which is typically 2000 times the aperture diameter as seen through the front of the lens, regardless of the focal length or the camera format. However, that figure of 2000 can vary widely, depending on the degree to which the image is enlarged and the preferences of the photographer.

[Drew Wiley]

Relative to comparable ANGLE OF VIEW, lets say you do use a 240 lens at f/22 on 4x5. But to get the same angle of view on 8x10, you'd need a 480mm lens - twice the focal length. So to obtain the same depth of field, you'd need to stop down to f/45 instead, if you use the same shutter speed and same film ASA. That's my level of math - 2X this or that ! Actual compositional issues regarding depth of field is something I judge with my eyes and a loupe on the ground glass itself. Hyperfocal theory and "circle of confusion" is a bunch of nonsensical confusion for sure, as far as I'm concerned. By the time you finish fussing with the math, the lighting has changed! I do sometimes employ hyperfocal theory in Med Format usage. But composition with a view camera needs to become a lot more intuitive and second-nature unless you want to risk unnecessary hurdles. Desired degree of magnification in the end use is also a determining factor. It always amused me when someone fussed around all day long trying to nitpick this topic in some studio application, and then had their 4x5 chrome published even smaller in some magazine than their original 4x5 film!

[Vaughn]

It's pretty easy to understand that if you take an image with a 240mm lens at f22 on your 4x5, then mount the lens on your 8x10 and re-take the image still at f22, the resulting images will have the same depth of field...
But in practice, to "re-take" the same 4x5 image with the same lens, one would have to move the 8x10 camera closer to frame it the same. This would give you less DoF even at the same f/stop...and a change in perspective.

The young Thomas Joshua Cooper approached his Holiness, Saint Adams with this question. Should he continue to chase the light with his old trusty 5x7, or should he move up to an 11x14? St. Adams in his wisdom spoke for the 5x7, for DoF issues arise when using normal to long lenses on 11x14. So it has been recorded.

[Bernice Loui]

More than just Depth of Field _ Depth of Focus, larger the film format on table top or similar non-infinity images, the larger the problems will be.. To believe larger film format always yields better image quality is simply not true. The overall image making system is a LOT more complex than that.

Bellows factor becomes an issue as image size on the GG or magnification increase. At life-size or 1 to 1, loss of two f-stops must be added to the taking lens aperture.

Image circle of the lens increases with magnification or images made at less than infinity focus grows the lens image circle. This often adds stray flare light inside the camera bellows that often reduces image contrast and alters film exposure. Cure is to use a lens shade that can be adjusted to cut off the excessive lens image circle. This demands carefully setting of the adjustable lens shade to achieve good results.

Highly recommend staying with 4x5 for table top work for a host of reasons from DOF, film cost, lighting needs, optics involved, camera movements needed and a whole lot more. Having done 5x7 and 8x10 table top stuff in the past, IMO 4x5 is a good format (specially color film, which is not the same as B&W film in many ways) if done properly. Know as the lens is stopped down to gain apparent focus, diffraction will negatively affect the image. Idea is to hold the taking aperture to no smaller than f22_ish if at all possible using camera movements and image size on film. If DOF become difficult to achieve, back up the camera-make the GG to film image smaller. Lenses achieve true focus at essentially a small flat plane to point, stopping down only provides the illusion of focus not actual focus. Other problems with sheet film sizes larger than 4x5, film flatness. Film flatness IMO is a very serious problem as film sizes grow. Problem is not as acute with contact prints from film formats 8x10 and lager. If the film is projection enlarged to make a print, that is when film flatness and more can become a very serious issue.. Don't think or believe scanning the big sheet of film then working with it in the digital domain will solve all image difficulties, it will not.


Bernice

[LFLarry]

Hi Bernice, you make some very solid points and I appreciate you sharing your knowledge and experience.

I absolutely will be staying with 4x5 for all tabletop work. I can't think of any possible reason to do anything else. I am very happy with my Linhof Technikardan and the reality is that I do this for my love of it. I will never be someone that generates an income from this and I am okay with that, but that doesn't mean I don't take this seriously. It is about me exploring, enjoying, learning, and creating images that I am proud of.

It would be good to hear your thoughts about the pros and cons of E-6 vs. C-41 for tabletop work?

I develop both at home in my Jobo, so either one is a non-issue from a development standpoint. I feel that I have a good post-production workflow for both as well. I know a lot of people struggle with getting colors right in post-production with color negative film, but I don't feel that I do.


Thanks

Larry




More than just Depth of Field _ Depth of Focus, larger the film format on table top or similar non-infinity images, the larger the problems will be.. To believe larger film format always yields better image quality is simply not true. The overall image making system is a LOT more complex than that.

Highly recommend staying with 4x5 for table top work for a host of reasons from DOF, film cost, lighting needs, optics involved, camera movements needed and a whole lot more. Having done 5x7 and 8x10 table top stuff in the past, IMO 4x5 is a good format (specially color film, which is not the same as B&W film in many ways) if done properly. Know as the lens is stopped down to gain apparent focus, diffraction will negatively affect the image. Idea is to hold the taking aperture to no smaller than f22_ish if at all possible using camera movements and image size on film. If DOF become difficult to achieve, back up the camera-make the GG to film image smaller. Lenses achieve true focus at essentially a small flat plane to point, stopping down only provides the illusion of focus not actual focus. Other problems with sheet film sizes larger than 4x5, film flatness. Film flatness IMO is a very serious problem as film sizes grow. Problem is not as acute with contact prints from film formats 8x10 and lager. If the film is projection enlarged to make a print, that is when film flatness and more can become a very serious issue.. Don't think or believe scanning the big sheet of film then working with it in the digital domain will solve all image difficulties, it will not.


Bernice

[Drew Wiley]

Film flatness is a non-issue if you use an adhesive or vacuum holder for 8x10 film. The film plane will be even more precise than using a conventional 4x5 sheet film holder. I really like the advantage of 8x10 film for prints 30x40 inch or larger. 4x5 will do the job; but 8x10 adds something special. Of course, very little commercial work demand this level of quality. But personal applications might deserve it. I only print optically, so there's no loss like in digital printing.
But it is interesting just how different compositional logistics can be between 4x5 and 8x10 depth-of-field strategy. Maybe flip a coin with 5x7 on each side.

[LFLarry]

Drew, when my health gets better, I hope to return to doing landscapes in the field again with my 8x10. I never thought about using adhesive before. Are you talking about adhesive in the film holders? If so, can you elaborate and share what you use? I would be interested in knowing more. I also print my 8x10 optically in addition to contact printing too.



Film flatness is a non-issue if you use an adhesive or vacuum holder for 8x10 film. The film plane will be even more precise than using a conventional 4x5 sheet film holder. I really like the advantage of 8x10 film for prints 30x40 inch or larger. 4x5 will do the job; but
8x10 adds something special. Of course, very little commercial work demand this level of quality. But personal applications might deserve it. I only print optically, so there's no loss like in digital printing.

[Drew Wiley]

The most easy kind of adhesive holder to make involves removing the film slide-in fins from a regular plastic Lisco or Fidelity holder, using a utility knife and straightedge, then carefully applying a sheet of reusable Post-It style adhesive film with permanent acrylic adhesive on one side, but low-tack repositionable adhesive on the front side. This is most commonly available as a particular 3M ATG tape. I can't remember the exact product number at the moment. I haven't tried European equivalent products. The thickness of the adhesive film itself is almost nil with respect to 8x10 focus. The amount of film bowing in a regular unmodified holder is a much greater factor. This type of adhesive seems to last many years if you don't get dirt or dust inside the holder. Mine are still working properly after 25 yrs of continuous use. Of course, you could eventually solvent-remove the old adhesive film and replace it if necessary. I reserve these holders mostly for color work, since I never enlarge black and white shots larger than 20x24, whereas I sometimes print color 8x10 shots larger. And having a history of Cibachrome printing, and now similar Fujiflex polyester medium, which holds extreme detail equally well, the precision of the adhesive holders has been a real advantage.

[joem]

Or you can cheat as I do and use a Quick Disk by Philipp Salzgeber for exposure compensation seems to work pretty well. Though I haven't gotten around to figuring out how to extend the range to use it for head and shoulder shots on 11X14.
For depth of field I look at the image and see what's there.

[Pere Casals]

Do you think hyperfocal is useful or relevant when doing product/studio work?

No...

Hyperfocal is for distant subjets in the scene, example, you want the mountains in the background in focus... then hyperfocal tells at what close distance other objects will be in also focus with the right settings. Using hyperfocal in the studio may lead to suboptimal results.

_____

Be aware that DOF formulas and calculators are only aproximate, specially in close distances and, depending on lens design, focus roll-off in the front and in the rear from the focused plane have their own nature and particular progressions.

In fact, there is a chart that plots that for a lens, "Through Focus MTF". This chart is often evaluated by Pro cinematographers, but amazingly it is pretty unknown in still photography.

197433
http://cinematechnic.com/optics/super-baltar


In cinematography a production may cost $200 million, so they have resources :)

The "Deep Focus" nature, for example, is a particular behaviour of a lens that is not explained by general DOF calculators, because those calculations are based in an ideal simple lens, while a real commercial lens is a complex artifact, compared.


So DOF calculators are very useful, but one also needs to understand how owned glasses work.

[ic-racer]

I am trying to better understand the reasons why there is less depth of field (DOF) with 8x10 vs. 4x5 at the same aperture.

I think I understand the basic principles of light and that larger film at the same aperture as a smaller format like 4x5 has less DOF.

Can someone help me better understand the "why" and the science behind this a little better?

Thanks
Magnification. This is important, because many DOF tables and equations leave OUT magnification!

[LFLarry]

hi. What app are you using in your phone that is pictured below?

Thanks




No...

Hyperfocal is for distant subjets in the scene, example, you want the mountains in the background in focus... then hyperfocal tells at what close distance other objects will be in also focus with the right settings. Using hyperfocal in the studio may lead to suboptimal results.

_____

Be aware that DOF formulas and calculators are only aproximate, specially in close distances and, depending on lens design, focus roll-off in the front and in the rear from the focused plane have their own nature and particular progressions.

In fact, there is a chart that plots that for a lens, "Through Focus MTF". This chart is often evaluated by Pro cinematographers, but amazingly it is pretty unknown in still photography.

197433
http://cinematechnic.com/optics/super-baltar


In cinematography a production may cost $200 million, so they have resources :)

The "Deep Focus" nature, for example, is a particular behaviour of a lens that is not explained by general DOF calculators, because those calculations are based in an ideal simple lens, while a real commercial lens is a complex artifact, compared.


So DOF calculators are very useful, but one also needs to understand how owned glasses work.




Sent from my iPhone using Tapatalk

[Pere Casals]

hi. What app are you using in your phone that is pictured below?


http://www.dl-c.com/DoF/

By Jonathan Sachs, for android (google play) and for windows

[Bernice Loui]

No amount of Depth of Field _ Depth of Focus calculations can equal direct viewing of the ground glass image with the camera set up, lighting set up and the lens stopped down to the taking aperture. While the mental masterbation of trying to calculate what Depth of Field _ Depth of Focus will appear like on the film image could be Academically curious and in ways secure and satisfying, the actual results on film might be quite different from what was intellectually expected.

Lesson is, learn to view the ground glass image with the lens stopped down to the taking aperture, there is NO substitute for this skill. No set of numbers can ever equal visual acuity coupled with experience based on what the finished print needs to look like.


Berice

[Drew Wiley]

There's the science of this, which might be fun to study and pontificate about in an armchair style, and devise all kinds of fancy charts, formulas, and programs about, and then there's the actual DOING of it, which requires intuitive knowledge devoid of all the complicated cobwebs.

[LFLarry]

Well said Bernice, and I particularly like the line "mental masturbation"... totally made my day.

I am heeding your advice and going to try to stay in the f/16 to f/22 range with my next round of photos. I went to the deli this morning and picked up some treats to photograph and then of course enjoy this weekend...





No amount of Depth of Field _ Depth of Focus calculations can equal direct viewing of the ground glass image with the camera set up, lighting set up and the lens stopped down to the taking aperture. While the mental masterbation of trying to calculate what Depth of Field _ Depth of Focus will appear like on the film image could be Academically curious and in ways secure and satisfying, the actual results on film might be quite different from what was intellectually expected.

Lesson is, learn to view the ground glass image with the lens stopped down to the taking aperture, there is NO substitute for this skill. No set of numbers can ever equal visual acuity coupled with experience based on what the finished print needs to look like.


Berice

[LFLarry]

I agree with that Drew. For me, I need to "understand it" so I can then make an intuitive process. If I have no basis for understanding then I struggle. Thanks for sharing your knowledge.




There's the science of this, which might be fun to study and pontificate about in an armchair style, and devise all kinds of fancy charts, formulas, and programs about, and then there's the actual DOING of it, which requires intuitive knowledge devoid of all the complicated cobwebs.

[Doremus Scudder]

I think this is fun.

We've got statements that range from, "format has nothing to do with depth of field," and, "the larger the film, the less depth-of-field for a given angle of view."

The interesting thing is, both are correct. The real players here are aperture and magnification.

I like to think about it this way: If we take a lens, say a 240mm lens with lots of image circle and make a photo from a given position on an 8x10 camera at, say, f/45, the depth-of-field will be X. If we swap out the 8x10 camera for a 4x5 camera, but keep the same lens, camera position, aperture and subject, and make another photograph, the depth-of-field will also be X. It's just that we now have a photograph with different borders; i.e., cropped in comparison to the larger photo. If we took our scissors and snipped out the 4x5 piece from the 8x10 film that corresponds to the image on the 4x5 film, we would have two identical images with exactly the same depth of field.

However, let's say we want to make a photograph with the same angle of view, i.e., the same borders, as the one we made on 8x10 film with a 240mm lens. Well, then we'll need a 120mm lens. The resulting image will have the same content as the larger one, but it'll be smaller. If we use the same aperture as the larger photo was made with, we'll have a lot more depth-of-field, however. Less magnification = greater depth-of-field. Or, we can duplicate the depth-of-field in the larger photograph by using a larger aperture; f/22 in this case. Turning this around, one can see that a smaller format often makes it easier to obtain more depth-of-field for a given image. It's simply that the image on the smaller format is smaller, i.e., less magnified and the depth-of-field is, therefore, larger. If depth-of-field is what you're after, a good guideline is to use the smallest format that will give you the image quality you need at the enlargement factor you desire. Going larger just makes getting the desired depth-of-field harder.

And, conversely, more magnification = less depth-of-field. Racking your bellows out for close-up work is similar to moving a projector farther from the screen: the image gets larger (more magnification). It follows then, that depth-of-field for any given lens/aperture combination decreases with bellows extension. Or, looking at it another way, the closer the subject is to the lens, the less depth-of-field we get from a given lens/aperture combination. That's why smaller apertures get used a lot for close-up-work and why arranging your subject so you can judiciously use camera movements to get the plane of sharp focus exactly where you want it is so important.

Best,

Doremus

[LFLarry]

This has to be the single best explanation for large format DOF that I have ever read. This one is getting printed out and put in my journal...

Thanks Doremus!


I think this is fun.

We've got statements that range from, "format has nothing to do with depth of field," and, "the larger the film, the less depth-of-field for a given angle of view."

The interesting thing is, both are correct. The real players here are aperture and magnification.

I like to think about it this way: If we take a lens, say a 240mm lens with lots of image circle and make a photo from a given position on an 8x10 camera at, say, f/45, the depth-of-field will be X. If we swap out the 8x10 camera for a 4x5 camera, but keep the same lens, camera position, aperture and subject, and make another photograph, the depth-of-field will also be X. It's just that we now have a photograph with different borders; i.e., cropped in comparison to the larger photo. If we took our scissors and snipped out the 4x5 piece from the 8x10 film that corresponds to the image on the 4x5 film, we would have two identical images with exactly the same depth of field.

However, let's say we want to make a photograph with the same angle of view, i.e., the same borders, as the one we made on 8x10 film with a 240mm lens. Well, then we'll need a 120mm lens. The resulting image will have the same content as the larger one, but it'll be smaller. If we use the same aperture as the larger photo was made with, we'll have a lot more depth-of-field, however. Less magnification = greater depth-of-field. Or, we can duplicate the depth-of-field in the larger photograph by using a larger aperture; f/22 in this case. Turning this around, one can see that a smaller format often makes it easier to obtain more depth-of-field for a given image. It's simply that the image on the smaller format is smaller, i.e., less magnified and the depth-of-field is, therefore, larger. If depth-of-field is what you're after, a good guideline is to use the smallest format that will give you the image quality you need at the enlargement factor you desire. Going larger just makes getting the desired depth-of-field harder.

And, conversely, more magnification = less depth-of-field. Racking your bellows out for close-up work is similar to moving a projector farther from the screen: the image gets larger (more magnification). It follows then, that depth-of-field for any given lens/aperture combination decreases with bellows extension. Or, looking at it another way, the closer the subject is to the lens, the less depth-of-field we get from a given lens/aperture combination. That's why smaller apertures get used a lot for close-up-work and why arranging your subject so you can judiciously use camera movements to get the plane of sharp focus exactly where you want it is so important.

Best,

Doremus

[Bob Salomon]

This has to be the single best explanation for large format DOF that I have ever read. This one is getting printed out and put in my journal...

Thanks Doremus!
Except the CofC is also a major factor of DOF!

[Drew Wiley]

The first two things I learned to ignore, and never have regretted ignoring, are "circle of confusion" and "normal viewing distance". The latter might be relevant to a book printer, where there is a sort of standardized viewing distance; but for display print applications it's utter bunk unless the viewer simply can't get physically close to the print. But "circle of confusion" is just one of those hypothetical niceties that seldom applies to real world photography. A ULF shooter might have all kinds lens diffraction issues under a magnifier, but is apt to stop way down and contact print anyway. In such cases, what is meant to be deliberately out of focus, and what is not, is really an esthetic choice related to compositional strategy and not held captive to the rules of optics. You aren't working for the NSA at fixed infinity focus from a spy plane! The same largely applies to 8x10 photography with long perspective lenses, which might get enlarged, but how much? Not generally that much, magnification wise. Soft focus types want everything turned in a circle of confusion for their own esthetic reasons. Simply inspecting your groundglass image at different potential f-stops, then homing in on details with a loupe, will tell your far more in mere seconds about image sharpness than hours and hours of nitpicking hyperfocal and circle of confusion hypotheses. The instant you apply view camera plane of focus tilts and shifts, all that gets a lot more complicated to figure out anyway in a pre- sense. Sinar cameras have yaw-free depth of field calibration features that might come in handy for studio tabletop photography, but are rarely of any real benefit for field photography where nature has designed the shape of topography rather than a billiard table company.

[alan_b]

I think this is fun.

We've got statements that range from, "format has nothing to do with depth of field," and, "the larger the film, the less depth-of-field for a given angle of view."

The interesting thing is, both are correct. The real players here are aperture and magnification.

I like to think about it this way: If we take a lens, say a 240mm lens with lots of image circle and make a photo from a given position on an 8x10 camera at, say, f/45, the depth-of-field will be X. If we swap out the 8x10 camera for a 4x5 camera, but keep the same lens, camera position, aperture and subject, and make another photograph, the depth-of-field will also be X. It's just that we now have a photograph with different borders; i.e., cropped in comparison to the larger photo. If we took our scissors and snipped out the 4x5 piece from the 8x10 film that corresponds to the image on the 4x5 film, we would have two identical images with exactly the same depth of field.

However, let's say we want to make a photograph with the same angle of view, i.e., the same borders, as the one we made on 8x10 film with a 240mm lens. Well, then we'll need a 120mm lens. The resulting image will have the same content as the larger one, but it'll be smaller. If we use the same aperture as the larger photo was made with, we'll have a lot more depth-of-field, however. Less magnification = greater depth-of-field. Or, we can duplicate the depth-of-field in the larger photograph by using a larger aperture; f/22 in this case. Turning this around, one can see that a smaller format often makes it easier to obtain more depth-of-field for a given image. It's simply that the image on the smaller format is smaller, i.e., less magnified and the depth-of-field is, therefore, larger. If depth-of-field is what you're after, a good guideline is to use the smallest format that will give you the image quality you need at the enlargement factor you desire. Going larger just makes getting the desired depth-of-field harder.

And, conversely, more magnification = less depth-of-field. Racking your bellows out for close-up work is similar to moving a projector farther from the screen: the image gets larger (more magnification). It follows then, that depth-of-field for any given lens/aperture combination decreases with bellows extension. Or, looking at it another way, the closer the subject is to the lens, the less depth-of-field we get from a given lens/aperture combination. That's why smaller apertures get used a lot for close-up-work and why arranging your subject so you can judiciously use camera movements to get the plane of sharp focus exactly where you want it is so important.

Best,

Doremus

It depends on where you end your analysis.

Taking this a step further to the print:

If you contact print both, the 4x5 and 8x10 will have different depth of field.
If you enlarge both to say 32x40, you're enlarging the 4x5 twice as much as the 8x10, and you'll see the depth of field is the same. :cool:

Another step further to different viewing distances...

Then there's grain, aberration, tonality differences with magnification...

[Drew Wiley]

The psychological perception of depth in a print introduces a whole other set of variables, which might unnerve someone trying to reduce everything to a math equation, but to someone like me represents just more enticing options in composition. Sure you can make everything the "same"; but it won't "feel" the same. You might be able to quantify that, you might not. I always amazed me how some so-called art expert couldn't tell a stylistically "correct" studied fake Van Gogh, or Pollock, or Picasso from the real deal without chemical analysis, etc. But some of these fakes to me just didn't "feel" right - you just see technique with no genius in them. A real Van Gogh almost instantly floors you - he put his whole soul into every single brushstroke; maybe that's what drove him mad, over-the-top. Dunno. I do know when a given subject just "feels" right in one given format and not another, or from exactly one particular perspective versus another. Something just falls into place on the groundglass, and even four inches to the left or right it doesn't. I thrive on that kind of cat and mouse game.

[Corran]

It depends on where you end your analysis.

Taking this a step further to the print:

If you contact print both, the 4x5 and 8x10 will have different depth of field.
If you enlarge both to say 32x40, you're enlarging the 4x5 twice as much as the 8x10, and you'll see the depth of field is the same. :cool:

Another step further to different viewing distances...

Then there's grain, aberration, tonality differences with magnification...

Doremus is correct.

If you are talking about a 4x5 shot with a 120mm lens at f/45 and on 8x10 with a 240mm lens at f/45, enlarged to the same size, no they will not have the same depth of field. If the 120mm lens was at f/22 they would (this ignores any differences in field curvature or other optical differences).

Viewing distance is an irrelevant thing. Not once have a gone to a gallery where the viewer was locked into one position. I have seen people view images with a loupe or magnifying glass.

Also I think folks forget that DOF is a bit of a mushy term. There isn't "in focus" and then immediately "out of focus." It's a range, based on some amount of "acceptably in focus." The reality is that only one point in space is truly in focus.

[Bernice Loui]

Drew is absolutely correct on this.

Perception of what is focused what is not focused and the personality of what is out of focus-vs-in focus is extremely complex. This is where I'll take absolute issue of oversimplifying this extremely complex perception by math only.. the math regardless of how much or how it has been applied CANNOT properly describe the emotional and visceral effects of image perception as this is NOT a numeric or equation expression language alone. At best the math can be used as part of the overall description of focus perception.

All this is why the very best design folks use a LOT more than just mathematical analysis.

The other most important aspect is learning the language of expression. Those versed in Math as a language can gain much of what is being expressed easily and rapidly in much the same way as one who is versed in music, visual arts, and much more.

~Challenge is learning these languages of expression and how they are used as a means of expression.~



Bernice





The psychological perception of depth in a print introduces a whole other set of variables, which might unnerve someone trying to reduce everything to a math equation, but to someone like me represents just more enticing options in composition. Sure you can make everything the "same"; but it won't "feel" the same. You might be able to quantify that, you might not. I always amazed me how some so-called art expert couldn't tell a stylistically "correct" studied fake Van Gogh, or Pollock, or Picasso from the real deal without chemical analysis, etc. But some of these fakes to me just didn't "feel" right - you just see technique with no genius in them. A real Van Gogh almost instantly floors you - he put his whole soul into every single brushstroke; maybe that's what drove him mad, over-the-top. Dunno. I do know when a given subject just "feels" right in one given format and not another, or from exactly one particular perspective versus another. Something just falls into place on the groundglass, and even four inches to the left or right it doesn't. I thrive on that kind of cat and mouse game.

[alan_b]

Doremus is correct.

If you are talking about a 4x5 shot with a 120mm lens at f/45 and on 8x10 with a 240mm lens at f/45, enlarged to the same size, no they will not have the same depth of field. If the 120mm lens was at f/22 they would (this ignores any differences in field curvature or other optical differences).

Viewing distance is an irrelevant thing. Not once have a gone to a gallery where the viewer was locked into one position. I have seen people view images with a loupe or magnifying glass.

Also I think folks forget that DOF is a bit of a mushy term. There isn't "in focus" and then immediately "out of focus." It's a range, based on some amount of "acceptably in focus." The reality is that only one point in space is truly in focus.

I wasn't disagreeing with Doremus. He outlined both cases correctly: same aperture and different aperture between 8x10 & 4x5. I was attempting to add the context that perception of different formats doesn't end at the negative, as Drew and Bernice more eloquently elaborated.

Viewing distance is certainly relevant to one's perception of a work. The experience of getting up close to a small print or book is very different to walking up to a wall-size print.

[Doremus Scudder]

Drew is absolutely correct on this.

Perception of what is focused what is not focused and the personality of what is out of focus-vs-in focus is extremely complex. This is where I'll take absolute issue of oversimplifying this extremely complex perception by math only.. the math regardless of how much or how it has been applied CANNOT properly describe the emotional and visceral effects of image perception as this is NOT a numeric or equation expression language alone. At best the math can be used as part of the overall description of focus perception.

All this is why the very best design folks use a LOT more than just mathematical analysis.

The other most important aspect is learning the language of expression. Those versed in Math as a language can gain much of what is being expressed easily and rapidly in much the same way as one who is versed in music, visual arts, and much more.

~Challenge is learning these languages of expression and how they are used as a means of expression.~



Bernice

Bernice,

I couldn't agree more. The term, "depth-of-field" is imprecise; it depends on what parameters are used to define it, which may or may not have a direct relationship to the impact of the image.

Nevertheless, the physics of optics are based on natural laws and don't change, so the discussion about how "depth-of-field" changes with aperture and focal length (and magnification and viewing distance, etc.) is still valid. It's just that once we understand how all that works, we still aren't much more enlightened about the expressive elements of a photograph. That's a different discussion, to which the science of optics applies more loosely. I don't consider, however, that examining the physical properties of how light works is an oversimplification as long as one remains aware of this. Within its limited sphere, physics can get pretty complicated :)

Best,

Doremus

[Drew Wiley]

On a very cold quiet day at the National Gallery, with almost nobody else around, I spent over three hours nose-up to a Vermeer. What's amazing about his work, as well as DaVinci's to some extent, is that he studied, and attempted to replicate in his own paintings, how the seeming "flaws" in actual human vision subtly contribute to our sensation and emotional perception of the world. We aren't perfect optical systems ourselves, and that's part of the beauty of it! There's a lot going on subliminally. Nuances (I'm certainly no soft-focus type). Few current trends disconcert me more than seeing some highly stitched digital scene involving the assembly of many short focal length shots into an immaculately sharp big image clear across the board. And ironically, this doesn't consistently add to a sense of depth of field, but interferes with it! Too much applied technique with too little real perception. It's like looking at wallpaper. That's why I spend way more time just looking through a big groundglass and assessing the feel, rather than actually shooting. The hunt is just as important as the kill. I want to feel what details should draw the eye into acute focus, and what portions should subtly withdraw themselves a bit. It's all about depth of field being strategized esthetically, for overall compositional purposes. And this should not be confused with ideas like shallow selective focus to enhance bokeh, as is often done with telephoto lenses. That's fine in certain cases; but with the kind of plane of focus and perspective controls we have with view cameras, plus such a huge selection of potential lenses, more sophisticated controls are possible. Nor does it mean I have ignored the science; rather, I regard that as just the carrots in a much more complex, and hopefully more tasty, stew.

[Doremus Scudder]

... Nor does it mean I have ignored the science; rather, I regard that as just the carrots in a much more complex, and hopefully more tasty, stew.

Well put!

[C. D. Keth]

I hope one wouldn't just ignore the physics behind this stuff. It's useful if you just tailor it to your needs. You can feel free to change those guidelines to suit your preferences, your equipment, and your output methods.

The circle of confusion, other than often living up the name "confusion," is just a variable to define your system's tolerance for sharpness. Nothing more. If your film is huge and you contact print something to hang up above a mantlepiece where you can't get very close, your CoC can be large. If you enlarge massively from an APS sensor and view the print from nose-distance, it will be tiny. In practice, you just do the best, finest work you can for the negative most of the time and, once in a long while, you have a weird situation where you try to stretch things to the limit and maybe you use this theoretical stuff. That is when you might be glad you paid attention and figured it out for yourself.

[Drew Wiley]

Nobody is ignoring the physics. But a lot of people ignore that it's a pair of eyes that are final arbiter of such things. What are you trying to achieve? If you want a 30X40 inch print, that's around 4X linear magnification from 8x10 film, 8X from 4x5. Even I can understand that math. You likewise need twice the focal length of lens for 8X10 use as for 4X5 if you want that identical perspective. But that means you have to stop things down twice as much to get the same depth of field (not factoring movements); in other words, if you used f/22 for 4x5 with an 180mm lens, you'd need f/45 for a 360 to obtain the same perspective and depth of field. Factors of two. I frankly don't give a damn about "circles of confusion" and "normal viewing distance"; and hyperfocal theory comes into my head only about twice a year when doing MF work. Nor do I pack a calculator. A simple magnifying loupe tells me everything I really need to know. I have a close friend who is a famous astrophysicist specializing in the physics of light, but he's never been able to take a decent picture with an ordinary camera.

[Vaughn]

That's part of the issue -- we have a pair of eyes and for the first 60 feet or so into a scene we see in 3D. Drew was mentioning about the painters exploring the 'faults' or characteristics of our viewing system (eyes/brain)...how do we as photographers compensate, expand, or otherwise manipulate our images to carry the 3D characteristics of the scene into our images? Depth of Field is only one tool.

[Drew Wiley]

Yep, the whole point of learning all the rules to begin with is that it becomes the basis to thoughtfully break every one of them afterwards, but not necessarily all at the same time. I could kick myself for turning down two exceptionally nice Julia Cameron platinum prints for $1600 apiece. They're probably worth 100K apiece now. But $3200 was a huge sum of money for a student back then, eating from dented cans and buying day old bread. People thought she was using funky lenses and so forth. But what she was really doing was focusing things just the way she wanted, matching the opalescent image on the ground glass to her expectation in the print. It wasn't "soft focus" or what people with telephotos today call "selective focus", but something way more nuanced that she felt was "just right". No damn formula can teach you that; you have to feel it.

[Vaughn]

... It wasn't "soft focus" or what people with telephotos today call "selective focus", but something way more nuanced that she felt was "just right". No damn formula can teach you that; you have to feel it.

I feel the same way about Linda Conner's work (POP instead of platinum). She was using the qualities of the lens, not just taking photos with it...a more conscience approach.

[Drew Wiley]

My own prints are quite different. They tend to look extremely sharp. But actually there are subtle differences between what is in fact in acute focus, and what is slightly not, deliberately leading the eye upon close inspection right where I want it. It's part of the compositional strategy. Might as well do that, cause the bigger the format you've got, the more you need to strategize depth of field, especially if you're a long lens addict like me. And I don't want it to be a mechanical act or veneer stamped on by a rote formula. I want to be in control of the detail rendition. And I judge that not only by the overall look of the ground glass image, but by what the loupe selectively informs me. So even though I don't do magical portraits like ole Julia, or even landscapes the way Linda C. does them, I am doing something analogous, better matched to my own intended look. Nothing annoys me more than seeing huge stitched images where everything tries to be equally in focus. Vermeer would roll over in his grave.

[Drew Bedo]

Ummm . . .My understanding of the subject (hope this actually helps):

I have an adapter lens board on my 8x10 that allows the lenses for my 4x5 to be mounted on the larger camera. My 210mm lens will cover the 8x10 format if not much in the way of movement is used. If I shoot a table-top composition with the 210mm on my 4x5 and then shoot the same composition with the same lens on the 8x10, the DOF is the same IF and only if, I shoot from the same distance. That means that on the 4x5, the lens functions as a longish "normal" focal length, but on the 8x10 it functions as a mild wide angle. Under these conditions, the size of objects on the GG qwill be the same on both cameras, but the 8x10 shows more the composition at the edges.

In general, comp;ositions shot with an 8x10 will be done with longer focal lengths than used on a 4x5 for the same composition . . . .longer lenses have shorter DOF.

Have I muddied the water?

[cowanw]

I don't think you have muddied the water, but I would add, in your scenario of same lens and position, is that the prints must also be the same ratio size as 4x5 is to 8x10 so that the end result represents the same magnification workflow.