Canon 100mm macro lens not very sharp :(

[dllavaneras]

I just got my 100mm macro lens today, so I first tried it out on my pet centipede. I attached the ring flash (Canon MR 14-EX), set the camera to manual, set the aperture to f16, the shutter speed to 1/125 sec and fired away.

After a few shots, I noticed that they weren't coming out as sharp as I thought they would. See the following examples to see what I mean:

Full pic:


100% crops




For comparison, here's a 100% crop from the kit lens at the same settings ( I think, if not, they're very close)


Is there anything I'm doing wrong? I've seen some spectacular pics with this lens, and mine don't come close. I've taken thousands of macro pics with my Canon S1 IS and they came out better (check my gallery for samples)

 

[libertyterran]

Were you hand-held in all these shots? As a rule of thumb: the shutter speed should be more or equal than twice the focal length (in this case 100mm x 2 = 200milisec at least). Another tip is that you should try to use a tripod+ball head combo when doing marco shot. Please correct me if I'm wrong though. GL!

 

[dllavaneras]

Were you hand-held in all these shots? As a rule of thumb: the shutter speed should be more or equal than twice the focal length (in this case 100mm x 2 = 200milisec at least). Another tip is that you should try to use a tripod+ball head combo when doing marco shot. Please correct me if I'm wrong though. GL!

Yes, the shot was hand held, but with the lower part of the macro flash resting on the ground. I also took a few shots at 1/200 today and they still didn't come out good. And a tripod is not an option for me, as I do field work and a tripod is too much of a hassle. I need mobility. :-/

 

[compuwar]

If this is digital, you're likely seeing the effects of diffraction at f/16. What do the shots look like at f/8?

 

[dllavaneras]

If this is digital, you're likely seeing the effects of diffraction at f/16. What do the shots look like at f/8?

The DOF is very narrow, so I'm not sure I'm seeing the effects of diffraction or if it's just outside the focus range. I'll try to take some more shots Thanks for the tip! BTW, why would I see the effects of diffraction at f16? I thought those showed up after f20...

 

[compuwar]

The DOF is very narrow, so I'm not sure I'm seeing the effects of diffraction or if it's just outside the focus range. I'll try to take some more shots Thanks for the tip! BTW, why would I see the effects of diffraction at f16? I thought those showed up after f20...

It depends on your MP and sensor size- on my D2x (12.4MP, 1.5x,) f/8.9 is where it starts to show up, and I try to avoid even going to f/11. Since it's pretty easy to just try f/8, and since f/8 is below the diffraction limits of pretty-much everything I'd just try that.

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm has the simple CF and MP calculator. A 1.6x CF body at 10MP starts having diffraction issues at f/9.3, and f/10 for a 1.5x CF body. At 10MP, only the 4/3rds systems start to hit diffraction limits below f/8.

 

[dllavaneras]

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

Thanks!

I did some more tests, this time using AF and the results were much better. The 400D's viewfinder isn't the best to manual focus, and I was getting too ambitious trying to focus in very low light.

Tomorrow, with daylight and a more confident mood, I'll take some more pics and have a definite answer. Thanks to all those who helped!

EDIT: I went on a four day trip and got to test out the macro lens. It's performance was phenomenal! Thanks you so much for the tip, compuwar! Here are a couple shots taken on the trip. All of them at f9, 1/200, ISO 100 unless otherwise noted.