Shooting at lesser magnification to increase DOF?

cactuspic · Post by **cactuspic** » Sun Jul 03, 2016 9:45 am

Recently, I was corresponding with another macro shooter who stated:

"...but the inherent narrow DoF, even at f/16, quite often leaves some of the subject outside of acceptable focus. Quite often, we will photograph a subject at less than 1:1 mag, but deeper DoF. We then crop to the same size as if shot at 1:1, but now with a better DoF."

I know depth of field can be an elusive concept when pressed, but the statement runs counter to my gut instincts. It seems to me that at a consistent fixed viewing distance, the depth of field is also a function of enlargement. It begs for an experimental test that I will be unable conduct until I get back into my studio (in another 2 weeks.) In the interim, my curiosity is burning. Has anyone confronted this question before? Can you improve depth of field over the depth of field attainable at 1:1 by taking the images at a lesser magnification and subsequently cropping the image to a comparable size?

Pau · Post by **Pau** » Sun Jul 03, 2016 10:29 am

If what you want is lower resolution and more noise...it will work, in fact it's like shooting with a smaller aperture (and so smaller NA) with the added inconvenience of using only a part of the sensor.

It's like inventing a perpetual movement machine, interesting at first though if you ignore Physics laws but...

cactuspic · Post by **cactuspic** » Sun Jul 03, 2016 11:44 am

Thanks, Pau. In applying the no free lunch rule, I was wondering where the payment would come from.

ChrisR · Post by **ChrisR** » Sun Jul 03, 2016 2:22 pm

You can get an extra benefit from cropping...

If you're photographig, say, a butterfly, whose wings are in a plane which is at an angle to your sensor, you can twist your camera to align them better.
Then you can crop off the side of the image you don't want.

Not as nice as a tilting lens, but hey.

cactuspic · Post by **cactuspic** » Sun Jul 03, 2016 4:59 pm

Thanks Chris. I do play with a homemade tilting macro lens, a reversed 90mm APO Componon, but it is not the quickest or most elegant to adjust when photographing lively critters.

ChrisR · Post by **ChrisR** » Sun Jul 03, 2016 6:37 pm

No it's not, is it! I've tried a few floppy bellows arrangements. Much easier to tilt the camera about (though it doesn't work as well) but it's hard to not use all those pixels we paid so much for even if we only need a small image.
This ties in with your other shooter's quote about "acceptable focus" and "better dof". It can be better to give up some sharpness in the sharpest parts to get more of the image recognizable - acceptably sharp. ?

cactuspic · Post by **cactuspic** » Sun Jul 03, 2016 8:06 pm

Agreed Chris. It's a decision I have made with the diffraction devil

many times...gladly.