Macro and camera format
I've been photographing some small but round objects, and running into DOF limits.
My question is, which is better, 35mm or 4x5 for macro? In my opinion, 4x5 is better than 35mm for most things, but as you go more and more final print magnification, 35mm becomes better. At what point is this?
Ignoring film grain and reciprocity failure issues, I understand that using the thin-lens equations for DOF, camera format does not matter when it comes to depth-of-field in the final print. If you want to make a 1-foot-wide print of an orange, then it should not matter what camera format or focal length lens you use to make it. Thin-lens DOF says that it doesn't matter, you can simply stop down the larger format more and always achieve the same DOF as the smaller format.
However, when you consider diffraction, larger formats are hit harder as print size increases (as total object-to-print magnification increases). As magnification from real-world object to printed image increases, eventually larger formats will lose out to smaller ones because you have to stop them down so far to achieve print DOF equal to the smaller formats that diffraction will take over at some point. What point is that? This ignores that there may be more diffraction when you enlarge the smaller format to the final print size.
Is there a rule of thumb as simple as "for FINAL, PRINT magnification greater than 10x, you are better off using 35mm than 4x5"?
Last edited by BetterSense; 12-30-2010 at 01:03 PM. Click to view previous post history.
f/22 and be there.
First of all I need to say that I don't know the answer but I am waiting for some knowledgeable people to respond.
However, when photographing 'normal' subjects where the image on the film is significantly smaller than real life, the smaller the format, the greater the depth of field.
Obviously at 1:1 the format is irrelevant as the image is always the same size as the object.
At greater than life size magnification though, I would be interested to find out if the rule reverses or stays the same. i.e. if you are filling the frame with the subject and it is larger than life size my gut instinct says that the larger format may now have the better depth of field.
..... but I could be wrong!
Recently I have been trying to photograph a small round seed pod at about 1:1 with my Olympus OM1 and 50mm Macro with extension rings. I put the lens on f/22 which is probably an actual f/45 or so at 1:1. The 8x10 proofs I made aren't impressively sharp, and I think I have eliminated camera/subject motion as a cause.
Since I use a 4x5 camera on a compound microscope (microphotography), I would say no rule of thumb applies, certainly diffraction has not caused me to use 35mm. And the trouble with your hypothesis is that you want to create an artificial playing field by ignoring granularity and view camera movements. You would also want to think about numerical aperture as well. Things are never equal. Use the tools that give you the result you want in the way you want. Whatever format you use, you will always be making compromises.
At f/22, diffraction is going to be very bad. You want to work at larger apertures and live with the narrow depth of field. The only real way to beat depth of field is to go digital and do z-stacking.
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First (and best) thing to do when entering the realm of macro is to forget about depth of field. There is none. So where you put focus becomes all important.
And it's not just that there is no DoF to begin with, stopping down a lens beyon a stop or two (in a futile attempt to gain some DoF) will seriously degrade image quality (no matter whether 4x5 or 35 mm format).
There are two approaches to macro: composition (or format) -driven and magnification-driven.
The first (composition-driven) takes the frame of the camera, and tries to compose the image inside it, no matter how large or small the magnification needed.
The second (magnification-driven) selects a desired magnification first, and choses the format that will best suit the image.
Both have their merits. The first makes do with the equipment you happen to have. The second ensures that image detail is not sacrificed to whatever equipment you happen to have.
Generally, the larger the format, the more cumbersome setting up a shot is, particularly when using the composition driven approach, since with increasing format, the magnification will have to increase as well to keep the image the same.
So a compromise is called for: use whatever format is most practical (i.e. smallest) and will still deliver the detail you are after.
For small prints, 35 mm format often is the best choice.
In reality, I suppose that it's not the format which makes the difference but it's the overall magnification from subject to final print size, the film format just being an intermediate step in the process. The greater the magnification, the more obvious the signs of diffraction.
Originally Posted by Q.G.
I'm trying to understand the compromises so I can choose them. I suppose I should try to setup a 4x5 shot enlarged to 8x10 and compare it with my 35mm shots. I'm not sure I even have a lens that will work, though.
Things are never equal. Use the tools that give you the result you want in the way you want. Whatever format you use, you will always be making compromises.
What apertures are recommended? Wide-open? FWIW, I did some brackets with the lens aperture ring set at f/5.6 and even at the plane of focus the difference is only slightly sharper than with the lens set at f/22.
At f/22, diffraction is going to be very bad. You want to work at larger apertures and live with the narrow depth of field.
In this case I can't use wider apertures because my subject is round. Even camera movements wouldn't help. The question is how can I maximize depth of field and what format is best for doing that...35mm or 4x5? Large format gives better resolution for large subjects. Is it better for macro? If not why not? At what point does it become "less good"?
Diffraction is related to the effective aperture, not magnification, otherwise a compound microscope would not work.
I would suggest z-stacking with a digital camera. Nothing will beat that. You can do that by scanning a film z-series. I believe CombineZ is freeware.
Originally Posted by BetterSense