Lens Sharpness Issue

[Gazer]

After having spent a considerable amount of time getting advice from many of you as well as reading countless reviews, I purchased a couple of lenses over the last few weeks to round-out my kit. Now that I've had the opportunity to play with them a bit, it has become apparent that I cannot get the same level of sharpness from them as I do from the original lens I purchased. I was wondering if anyone might be able to provide a little insight as to why. The original lens I purchased was the EF100 f/2.8 macro which has been fantastic. My two more recent lenses are the EF-S15-85IS and the EF300 f/4 IS. My camera is the EOS40D. I didn't really expect the zoom to match the macro lens in regards to sharpness, but I did have grand expectations for the 300.

Once again, thanks for any input.

[RecurrentNerve]

Examples with EXIF might help a diagnosis.

[dcclark]

Yes, examples please -- it would help if you could identify some spots which aren't sharp enough.

With the 300mm, I suspect that you might be running into atmospheric disturbance. Even on a clear day, a long enough lens will be affected by normal movement of the air, especially if you're focusing into the far distance.

[Gazer]

Sorry - just now getting back to my pc.

Hmmm ... I hadn't given atmospheric disturbances a thought until you mentioned it.

Here is a comparison of the 100macro and 300 IS (which is typical of what I've seen regarding performance). What I'm displaying is how these lenses are performing for me - consistently.

Cam1c image: 100macro, f/5.6, 1/800sec, 100iso

Cameron3 image : 300 IS, f/5.6, 1/400 sec, 100iso

[dcclark]

I would say that the 300 image has acceptable sharpness, for what is apparently an action shot. Also, don't forget that you're shooting a much longer lens at a shorter shutter speed, which won't help.

Being different subjects in different settings, other factors could be that your autofocus wasn't working as well with the non-posed subject, or different camera-holding technique.

You really need to compare both in the same setting, with the same subject, same light, at the same time. Try setting something up where you can take a photo with both lenses, one after another, and then compare.

[inkista]

Just my opinion, but the 300mm shot looks like a misfocus issue. Look at the surface of the water to the left of her face. There's sharpness, it's just not where you want it to be. Don't forget that with the longer lens, you're also possibly dealing with a smaller DoF. How were you focusing the shot?

Also, while I love the hell out of my 400mm f/5.6L USM, my EF-S 60mm Macro is still sharper.

And with the 15-85, have you tried stopping it down to f/8?

[spazoid1965]

I would set up a controlled test on both lenses. Be sure and use a tripod . The longer lens will be more prone to show any movement.

[Gazer]

I agree that I should be providing better examples (same subjects, exif, etc.) for the purpose of getting feedback from you all. Unfortunately, all of my files are currently in storage right now and all I had were a few jpegs on this pc. My focussing technique usually comprises of focus and then re-compose prior to taking the shot. Perhaps I need to practice a little more with the longer lens, as well as conduct some tests as spazoid suggests.

Thank you all for your input.