Is there any real utility to ULF?

[sanking]

Keeping film flat in ULF film holders has never been an issue for me. Contrary to a statement made somewhere above, Depth of Focus is less of an issue with larger cameras. It, and just about every other camera specific technical problem, gets to be more of an issue with the smaller cameras due to the amount of enlargement that is required.

You are absolutely right about this. Depth of Focus is much less of an issue with larger cameras, where longer lenses are typically used, than with medium format and 4X5 and 5X7. Anyone who may doubt this should carefully read Lambrecht and Woodhouse's article on the subject in their book Way Beyond Monochrome, and do their own figures for the focal length of the lens being used.

To avoid any confusion, please note that Depth of Focus is not the same as Depth of Field, and is calculated differently.

Sandy King

[Dan Fromm]

Bill, in past discussions you've been completely impervious to the idea that physical limits exist and that they can be found by calculation. In fact, you were worse than impervious. You denied limits' existence.

What caused your change of heart?

And why did you pick this fight? Or, to put it another way, what launched you on your current crusade?

[John O'Connell]

As I recall from VCT, the depth of focus formula indicates that depth of focus increases with magnification (or, as the term is generally used here, "focal length"). As far as I know, depth of focus is rarely an issue in formats larger than 4x5---unless, like me, you occasionally load film in front of the septums . . .

Don’t have much to add, otherwise, because the argument is apparently over reproducible lp/mm in formats used for processes where the final print can only display 20 lp/mm if contact printed with a test chart.

[bglick]

> Depth of Focus is much less of an issue with larger cameras, where longer lenses are typically used, than with medium format and 4X5 and 5X7

DOFocus is a function of f number, parallelism and film flatness. I agree of these three variables, film flatness is the least significant. As I mentioned above, I would be more concerned with parallelism as the larger the camera, the more of technical challenge it is to keep the standards parallel on both axis.


But with ULF, DOFocus is very application specific. If you contact print the film, DOFocus becomes much less critical - agreed. But if you do 120" enlargements like a poster mentioned above, DOFocus with ULF is extremely critical, specially if you shoot a non depth shot and open up the apt. to reduce diffraction effects. So again, no one right answer here, it depends on the application.






> Using a large format camera or an ULF camera can be about Craftsmanship--Craftsmanship in the use of the equipment and Craftsmanship in the use of the materials.


David, I fully agree, and I tried to stress this 3x above, but some people continued to ignore it. I love ULF cameras, just like I love a Lamborghini's and Model T's. They all have their place.





> What caused your change of heart?

Hi Dan, I can only assume you have me confused with someone else....

[Jorge Gasteazoro]

Using a large format camera or an ULF camera can be about Craftsmanship--Craftsmanship in the use of the equipment and Craftsmanship in the use of the materials.

Some of the issues discussed here are typical arguments against using ULF cameras, but in practical use they are not relevant.

The idea that Parallelism is a potential problem with large format or ultra large format cameras is funny, unless the camera has no ground glass, only then would it would be an important issue.

Keeping film flat in ULF film holders has never been an issue for me. Contrary to a statement made somewhere above, Depth of Focus is less of an issue with larger cameras. It, and just about every other camera specific technical problem, gets to be more of an issue with the smaller cameras due to the amount of enlargement that is required.

I have some process lenses that cover film sizes much larger than 8x10 that are sharp enough for any film format size. It simply isn't true that there aren't any lenses that cover larger than 8x10 that are sharp. And yes I mean sharp for any 2-D or 3-D subject located somewhere between my camera and infinity, or even at infinity.

Modulation Transfer Functions are irrelevant to almost anyone using large format or ULF cameras to make a photographic print. There are many, far more important, user based criteria that determine the suitability of the final image than MTF curves.

I have never stood behind my 8x10, 11x14 or 12x20 camera and, while looking at the ground glass, thought that there was not enough depth of field to make the image. In fact the only time that I have ever thought about depth of field issues is when people use it to say that bigger cameras are not as useful as smaller cameras for making photographic prints.

The possibilities within digital imaging are of no significance to the potential user of ULF cameras.
The utility of the ULF camera is solely based on the printmaker’s desired results.

David, while your response is very good you are responding to someone who obviously does not own or know how to use an ULF camera, this was clear from the first post.

For example, as I implied David very conveniently fails to talk about depth of focus as related to film flatness, and when he does he talks about it like it was something so incredibly difficult to understand that only he can do it and does not want to confuse us.

I disagree with you in that depth of focus is not relevant, in fact it is relevant in ULF because the depth of focus is so great that it allows us to not worry so much about film flatness or parallelism. For example, if we accept that for an ULF shot an acceptable circle of confusion is 1/150 then we see that for a shot taken at f/45 the depth of focus is 0.6 of an inch. That is about 13 mm.... no ULF holder, not even the latest by AWB have that much play. Using the same circle of confusion, if you then use f/64, the depth of focus is almost an inch...lol. What David does not seem to understand is that depth of focus increases with film size, since the circle of confusion increases with it. So for a 20x24 shot, the circle of confusion reaches the theoretical limit of 1/100.

So, with one variable that he very conveniently forgot to mention we have taken care of all his objections. Film flatness...no big deal with almost a half an inch to an inch if you use small apertures. Depth of field...well, here we go again as the gipper said. Is taken care of with small apertures. Parallelism?...funny, I thought this was the purpose of view cameras, to be able not to have parallel standards. Given that the depth focus increases with size, it is the reason why we can move the standards, specially the front standard and still have a capability of having everything sharp at the film plane.

As to the lenses and their MTF curves, etc. Well, all that one needs to do is look at the negatives.

[Jorge Gasteazoro]

DOFocus is a function of f number, parallelism and film flatness. I agree of these three variables, film flatness is the least significant. As I mentioned above, I would be more concerned with parallelism as the larger the camera, the more of technical challenge it is to keep the standards parallel on both axis.

Wrong, depth of focus is a function of f stop, and circle of confusion. The formula is DFo=2Xf/stopXCoC.

[Jorge Gasteazoro]

As I recall from VCT, the depth of focus formula indicates that depth of focus increases with magnification (or, as the term is generally used here, "focal length"). As far as I know, depth of focus is rarely an issue in formats larger than 4x5---unless, like me, you occasionally load film in front of the septums . . .

This is not right John. Here are the rules for depth of focus.

Depth of focus increases as the lens is stopped down.
Depth of focus increases as object distance decreases
Depth of focus is not affected by focal lenght.
Depth of focus increases as film size increases.

[John O'Connell]

Jorge, there is some difference of opinion on the correct formula for DOFocus.

VCT apparently states that depth of focus = 2(f-number)(acceptable circle of confusion).

But, a quick check indicates that the formula provided may be an approximation for infinity, leaving out a term presumed to be negligible for distant subjects:

"depth of focus is two times the f-number times the circle of confusion times the quantity of one plus the magnification factor"

or

"U = 2NC(1+M/P)"

So DOFocus does appear to vary with magnification as image size approaches and exceeds subject size.

[Jorge Gasteazoro]

Jorge, there is some difference of opinion on the correct formula for DOFocus.

VCT apparently states that depth of focus = 2(f-number)(acceptable circle of confusion).

But, a quick check indicates that the formula provided may be an approximation for infinity, leaving out a term presumed to be negligible for distant subjects:

"depth of focus is two times the f-number times the circle of confusion times the quantity of one plus the magnification factor"

or

"U = 2NC(1+M/P)"

So DOFocus does appear to vary with magnification as image size approaches and exceeds subject size.

You are correct John when you are talking about close up or macro work. Which makes sense, right? I have yet to see someone using an ULF camera to make photographs where the subject is 1:1 or greater. Although I don't discount it, clearly someone doing macro work would have to worry about not only depth of focus, but film flatness as well as difraction, since it would require extremely small apertures to obtain an acceptable depth of field.

In the case we are talking about, we are concerned moslty with low magnification ratios where typically apertures of f/45 to F/64 are commonly used. Unlike it was made belive by the previous poster these apertures do not cause difraction. Another reason why it is obvious this person is not familiar with the use of ULF cameras. If you look at the f/64 of a lens mounted in a copal 3 shutter, you will see it is still a big hole..

[Nathan Potter]

Yep, John is correct. You can pick an acceptable circle of confusion, then the depth of focus is 2c'N(1+m) where c' = acceptable Image of confusion
N = effective f/no.
m = the magnification factor

and providing that c' may depend on the focal length of the lens.

Nate Potter