I am thinking of switching to full frame because for other work (in particular, night photography), primarily to get the better high-ISO noise performance. I've been perfectly happy with a crop sensor for macro work and don't want to make that more difficult. So, I tried to figure out the effect on macro work, and I realized I was not sure. Since some folks here shoot with both, I figured this would be a good place to post, even though this is an equipment question.

I would keep using the same lens, my 100mm L. I would be switching from a 50D to a 5D, I think.

So, here is what I THINK is true. Please correct me if I am off.

1. Minimum focusing distance would not change
2. Magnification at minimum focusing distance would not change. A 1 cm bug would still be 1 cm on the sensor.
3. FOV changes, of course, so the 1 cm bug would fill less of the frame.
4. DOF (assuming the same distance to the subject) would decrease by a factor of 1.6. I vaguely recollect that Brian once posted that this is roughly the effect of one stop. If so, it would be easy to close down one more stop, given less effect of diffraction and better high-ISO performance.
5. Assuming shots taken at minimum focusing distance, a crop of the FF image to match the FOV of the crop would have a different pixel density, depending on the cameras. Going from my 50D to a 5D, FF would provide lower pixel density.

Is this right? I would be grateful for any corrections. I want to make sure I will not be messing up macro work if I decide to take the plunge.

Thanks very much.

Dan

Think that's about right on all counts.
Brian v.

Brian,

Thanks very much. Now that you have considerable experience with a 5DMkII, would you recommend crop over FF for macro to someone with a blank slate? My camera has to be replaced anyway, and the two competitors are the 7D and 5DMkII. (Unless I stumble on a patron, I don't see a MkIII on the horizon.)

Dan

Originally Posted by paddler4 Brian, Thanks very much. Now that you have considerable experience with a 5DMkII, would you recommend crop over FF for macro to someone with a blank slate? My camera has to be replaced anyway, and the two competitors are the 7D and 5DMkII. (Unless I stumble on a patron, I don't see a MkIII on the horizon.) Dan

Difficult question. I would certainly recommend using a 5Dmk2 with an MPE-65 lens - Ive not used my 5dmk2 with a normal 1;1 macro lens at all but have just bought a 600D to use with my tamron 90 and have been very happy with that.

I suspect your decision may well depend on the other uses you want the body for.
Brian v.

Brian,

Thanks again. Very helpful. For other uses, the tradeoff is clear: far better AF in the 7D, far better low-light performance and lower noise with the 5DMKII. However, it is very helpful to know that in your opinion, there is no clear winner for 1:1 macro. (2:1 with tubes is the highest I ever go, and I don't see an MPE-65 in my future.)

Dan

Dan

also remember dof is shallower on full frame compared to cropsensor. better for isolating backgrounds , especially butterflies with 100mm
think i use 100mm more than mpe at moment.