Macro and camera format

[Dan Fromm]

The relationship between NA and f/ number is NA = 1/(2f) where f is the f/ number. f/0.5 means NA =1, and so on.

NA is defined concisely here: http://micro.magnet.fsu.edu/primer/a...maperture.html

[Diapositivo]

If the problem is depth of field, I suggest looking for a solution with movable planes, like a view camera, that allows you to use the Scheimpflug law.

Some bellows exist that allow you to turn - in the sole domain of macro photography - you camera in a "view" camera, with all movements. I think some of those, for 135 format, even have support for automatic diaphragm mechanism (diaphragm stays open for focusing and closes automatically when you take the picture).

Those bellows should exists both for 135 and 120 film cameras, but I suspect they are easier to find for 135.

I never used them so I am only giving a theoretical suggestion here.

Fabrizio

[dynachrome]

If you do not have a sufficiently short lens on a view camera then you will need a huge amount of extension to get the magnification you are looking for. In any format not every lens is well corrected for macro work. With enough extension the desired magnification can be achieved but the image quailty may not be very good. In any macro situation you need to to align the film plane with the most important part of the subject to make the best use of the available depth of field. A typical 50-60mm macro lens for 35mm use will not be at its best at f/22. Some bellows usits for 35mm cameras have front standards with movements. These include the Nikon PB-4 and the Minolta Auto Bellows III. These movements can be used to fine tune depth of field. There was an interesting Spiratone bellows with interchangeable mounts which had movements.

In any situation where medium format or large format is being considered for use in preference to 35mm, you need to see whether the size of the subject on the negative/slide is larger than what you would get with 35mm. A subject which is 24X36mm in size and which is shot at 1:1 on 35mm film will give an image area of 24X36mm. If your medium format set-up gets you the same 1:1 magnification then the image area of the subject will be the same 24X36mm on film. In this example there was no benefit in using the larger format assuming that both cameras had the same film type in them. With the 6X9 format, for example, you would need 2:1 magnification to get the same subject to 48X72mm on film. How much image quality you would get because of less enlargement of the film would depend on how large you wanted to make the final print. For black & white work you have films like Imagelink HQ which can withstand great degrees of enlargement without showing grain. Color films like Ektar and Velvia 50 aren't nearly as good as Imakelink HQ when it comes to grain but are still very good. Once Kodak discontinued Kodachrome 25 it became necessary to go up in format for certain color work.

As a general proposition the smaller your subject the easier it is to handle with 35mm equipment. The 35mm equipment is more flexible and allows you to adapt many types of lenses, bellows, extension tubes etc. All of my medium format SLRs are Bronicas with electronically governed leaf shutter lenses. I could get a bellows for any of the three formats but a Mamiya 645 with a focal plane shutter would be more easily adapted for higher magnification close-up work.

[BetterSense]

I ended up shooting with my 4x5 monorail and my Rodenstock 135mm enlarging lens, turned around backward, at f/32, 1:2 magnification onto film (f/90 effective). The contact prints look pretty nice so far but I haven't enlarged them yet. I don't have a fancy bellows setup for 35mm and I needed significant geometric distortion correction. My bellows is just barely enough, after I cut a custom lens board out of cardboard with 2 inches of down shift built in.

I still don't fully understand the fundamental differences between shooting to a smaller magnification on the negative and enlarging more, versus shooting to a larger magnification on the negative and enlarging less. Is it better to shoot 1:1 on 4x5 and enlarge to 8x10 or is it better to shoot 1:4 on 8x10? I'm still not sure.

[Sirius Glass]

For a given image size, regardless of the format and focal length, there is a DOF for each f/stop.
Therefore:

A 1" image on in 35mm film will have the same depth of field for a 35mm, 50mm, 100mm lens. The perspective will be different.
A 1" image on in 4"x5" film will have the same depth of field for a 90mm, 150mm, 200mm lens. The perspective will be different.

You are photographing a sphere. Therefore shifts, tilts, ... will not change the DOF.

Now we have eliminated movements. The first question is what size image do you want on the film, and hence the amount of enlargement involved. This eliminates the question of grain as you specified in your first post.

The second question, given that either the 35mm or the 4"x5" cameras can be set up and focused on your subject, you can now take a longer exposure and increase the exposure time in a trade off for DOF. Therefore, which camera do you choose to use?

The smallest 35mm f/stop is typically f/16 with the best performance without diffraction is around f/8.
The smallest 4"x5" f/stop is typically f/32 with the best performance without diffraction is around f/22 or f/16.

In summary, for a given image size on film the focal length does not matter. DOF is a function of f/stop.
The object is a sphere and therefore movements will not help.
To increase DOF, lengthen the exposure.
So pick the camera which will work for you, given any diffraction issues that you have.

Steve

[Dan Fromm]

Um, Steve, doesn't magnification matter too? Or are you talking about effective aperture?

Transparency, all that movements do is shift the plane of best focus around. This allows better use of the depth of field. At the magnifications and set apertures the original poster is using there is very little DoF. Movements won't create more.

[Q.G.]

Um, Steve, doesn't magnification matter too?

That's covered in that "For a given image size".

[Sirius Glass]

Thank you Q.G. for answering for me. I specifically said "For a given image size" for a reason that you are wise enough to understand why it was included. I hope that 2011 is a better year than 2010 for you!

For those that missed it. "For a given image size" takes out format questions.

Steve

[Diapositivo]

Well, we don't know how small are the objects that the OP is going to photograph. I certainly agree that, if they all are spherical, there is no point in rotating the focus plane. One assumes a photographer does not only take pictures of exactly spherical objects, and if they are not all exactly spherical (watches, jewels, who knows) a rotation in focal plane might give a substantial help for the final image quality (let's say aligning the focus plane with the dial - thickness of the watch). But I never used a bellows with movements, althought I've read it helps, I would be glad to be able to give an answer validated by experience.

IIRC there was a Kenko bellows in the eighties (for 35mm) that had movements in both standards.

Fabrizio

[Diapositivo]

Well, we don't know how small are the objects that the OP is going to photograph. I certainly agree that, if they all are spherical, there is no point in rotating the focus plane. One assumes a photographer does not only take pictures of exactly spherical objects, and if they are not all exactly spherical (watches, jewels, who knows) a rotation in focal plane might give a substantial help for the final image quality (let's say aligning the focus plane with the dial - thickness of the watch). I never used a bellows with movements though, althought I've read it helps, I would be glad to be able to give an answer validated by personal experience.

IIRC there was a Kenko bellows in the eighties (for 35mm) that had movements in both standards.

Fabrizio