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BetterSense
12-30-2010, 11:51 AM
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"?

Steve Smith
12-30-2010, 11:59 AM
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!


Steve.

BetterSense
12-30-2010, 12:31 PM
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.

Hikari
12-30-2010, 12:31 PM
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.

Hikari
12-30-2010, 12:34 PM
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.

Q.G.
12-30-2010, 12:41 PM
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.

Steve Smith
12-30-2010, 01:16 PM
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).

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.


Steve.

BetterSense
12-30-2010, 01:19 PM
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.

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.


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.

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.

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"?

Hikari
12-30-2010, 01:21 PM
Diffraction is related to the effective aperture, not magnification, otherwise a compound microscope would not work.

Hikari
12-30-2010, 01:27 PM
The question is how can I maximize depth of field and what format is best for doing that...

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.

David A. Goldfarb
12-30-2010, 01:49 PM
Focus stacking is a great technique, but it's off topic for APUG, so the question for this forum is, how to do what you want using traditional techniques.

Camera movements are a plus, if the subject lends itself to it. At very high magnification (say more than about 6x comparing the size of the object to the size of the image on film), DOF is going to be razor thin, so it's all about using the DOF you have most effectively. Diffraction does become an issue at higher magnifications, because the effective aperture is in fact much smaller than the aperture as set on the lens, so you may choose a wider aperture to get the sharp part of the image sharper, even if it costs you some DOF.

There are other problems when you go up in format--mainly you need more light. If you are using artificial light, then put the light as close as possible to the subject--really close, presuming the heat from your light source won't destroy the subject--to get as much out of the light you have. You need a really solid tripod, head, and ideally a macro focusing rail unless you are using a view camera with focus on the rear standard, and you may want to do things like sandbag the camera and add weight to the tripod. You may need to be concerned about the solidity of your floor. This is true whether you are using strobes or continuous lighting, because even with powerful studio strobes, you will likely need multiple pops to get enough light for the exposure.

Hikari
12-30-2010, 01:57 PM
Focus stacking is a great technique, but it's off topic for APUG, so the question for this forum is, how to do what you want using traditional techniques.

I am sorry. I did not realize shooting a series of film stacks, scanning them, and then stacking them is off topic.

BetterSense
12-30-2010, 03:53 PM
There are other problems when you go up in format

At least I understand all those problems. I don't fully understand the effect of camera format on the final print's DOF and sharpness. I still don't understand the merits of shooting to a smaller format and enlarger more, versus shooting to a larger format and enlarging less.

Hikari
12-30-2010, 04:51 PM
At least I understand all those problems. I don't fully understand the effect of camera format on the final print's DOF and sharpness. I still don't understand the merits of shooting to a smaller format and enlarger more, versus shooting to a larger format and enlarging less.

If you are looking at equal DoF and equal relative image size (unequal f-numbers and unequal magnification), then there is no advantage to format in macro photography (1x or greater). The only advantage is in granularity and resolving power of the film on appearance.

BetterSense
12-30-2010, 06:32 PM
Sorry I don't understand. I'm trying to decide the advantages between 35mm and 4x5.


If you are looking at equal DoFI am looking at equal DOF between the two formats...I want to have my entire subject sharp, if possible.


and equal relative image size
The final prints between the two formats will be the same.


then there is no advantage to format in macro photography (1x or greater)

Ok, that's what I thought but I'm still not so sure.

Consider 3 scenarios:

Consider my little seed pod I'm photographing; it's about golf-ball-size and roughly spherical.

1. Say I'm using a 4x5 camera and I set it up 1:1 so the image of the seed pod is 1-inch (life-size) on the 4x5 film. I adjust my aperture to get 1/4 inch of DOF. Then when I print I enlarge the negative until seed pod to 10-inches wide on the print, and crop the print to 11x14.

2. Say I'm using a 4x5 camera and I set it up 4x magnification so that the seed pod is 4 inches wide on the film. I adjust my aperture until the DOF is 1/4 inch, same as before. Then I enlarge the negative until the seed pod is 10-inches wide on the print, and crop the print to 11x14.

3. Say I'm using a 35mm camera and I set it up .25x magnification so that the seed pod is 1/4 inches on the negative. I adjust the aperture until the DOF is 1/4 inches. Then I enlarge the negative until it's 10-inches wide on the print, and crop the print to 11x14.

What differences in results can I expect? Theory predicts that I will have to use the smallest aperture for scenario 2, correct? Ignoring things like film grain, reciprocity and light issues, what differences can I expect the prints to have?

Hikari
12-30-2010, 06:49 PM
No difference. Since we are talking about macrophotography and you are equalizing the object space, the image space printed at the same scale should turn out the same.

Yes, scenario 2 gives you the smallest effective aperture (f-number). But all three scenarios will have the same numeric aperture.

keithwms
12-30-2010, 07:09 PM
No format is any better than another for macro. What matters is which gear best enables you to see what you want and consistently delivers the goods without too much fuss.

My preferred macro system is the mamiya rb67. It is very stable, uses leaf-shuttered lenses, and features bellows focusing... all helpful for macro. If I need tilts or back focus, I will sometimes put an rb lens (or the fast rz 110/2.8!) or Nikkor 120 AMED lens on a rittreck 5x7, that is a nice, stable platform. Sometimes you really do need tilts, if you are fighting for every last micron of DOF. That plus other rear movements and back focus can be very helpful.

Another macro system that I enjoy is the mamiya 645 pro with the 80/4 macro lens, that is good fun. I like the lens so much that I sometimes use it on 35mm as well.

David A. Goldfarb
12-30-2010, 07:53 PM
Focus stacking is a great technique, but it's off topic for APUG, so the question for this forum is, how to do what you want using traditional techniques.

I am sorry. I did not realize shooting a series of film stacks, scanning them, and then stacking them is off topic.

Indeed, hybrid digital/analogue topics are off topic for APUG, but are completely appropriate on our sister site, http://hybridphoto.com

BetterSense
12-31-2010, 11:39 AM
Yes, scenario 2 gives you the smallest effective aperture (f-number). But all three scenarios will have the same numeric aperture.

I thought that numeric aperture was just another way to express the same quantity that is expressed with f-number. How can the numeric aperture be the same in all three scenarios when there are 3 different in-camera magnifications, all with the same DOF?

Hikari
12-31-2010, 12:05 PM
I thought that numeric aperture was just another way to express the same quantity that is expressed with f-number. How can the numeric aperture be the same in all three scenarios when there are 3 different in-camera magnifications, all with the same DOF?

Numerical aperture (NA [sorry, my mistake]) is the angular size of the entrance pupil from the object plane. It is an object space factor. f-number exists in the image space.

f-number can be thought of two ways: the focal length divided by the entrance pupil or the angular size of the exit pupil from the image plane. An f/5.6 aperture presents the same angular light cone to the image plane regardless of the focal length. This is why depth of focus (the tolerance at the film plane) is only dependent on the f-number.

Likewise in the object space where the sample is, depth of field is dependent on the numerical aperture. Just like the f-number, the angular size of the entrance pupil is dependent on the dimension of the aperture and the distance to the object plane. You will find that each one of your scenarios having the same DoF will have the same numerical aperture.

Numerical aperture also is related to the resolving power at the object plane, just as the f-number is related to the resolving power at the image plane.