How Does Aperture Effect Sharpness?

[Fotoman!]

Hey guys, Ok, here is my situation. I shoot a lot of indoor basketball. Due to the lighting I am always at 2.8 on my Canon 70-200mm F/2.8L lens. With an ISO of 3200 on my Canon 7D I can hang around 800-1000 shutter speed. I have no problem stopping motion. For the most part, the photos are very good (at least I think so). However, I don't think of them as being "crisp". I mean, they look a little soft to me. In post processing (PSE 8) I increase the sharpness but not too much. Seems the more I do the more noise I begin to introduce to the photo. I have read before that you get better sharpness the less aperture opening you have. Well, with me needing all the light I can get... that won't work for me. Is is a correct statement that sharpness and aperture are most definitely related? Any ideas on how to improve sharpness in my situation?

Thanks all.

[Jim Bryant]

post some for us to see

[RichardTaylor]

As a guide lenses perform better when used at approx 2 stops from the maximum aperture.
"Sharpness" also depends on contrast (within the subject itself and against the background) light.

When you are sharpening are you sharpening the colour channels as well as the luminance channel? Try sharpening just the luminosity channel. I don't know how you do that in PSE however this may help.

Sharpening 101

[sk66]

Generally 1-2 stops down is maximum sharpness...beyond that stopping down only increases DOF. I would guess you could easily step down to f/4 or even f/5.6 (shutter speeds of 400/500 @ f/4 ISO 3200) That should be fast enough to stop motion and increase sharpness..

But really, you are probably just suffering from "pixel peeping" more than anything.

[teaking]

And I think DOF decreases at larger apertures and with magnification so the actual point of focus could be relatively small and if not focused bang on may be just out.

On the PP front you could try a high pass filter for sharpening this tends to create less noise as it sharpens edges and allows selective sharpening which can give better results.

[BCampbell]

Depends on a lot of things.

Are you shooting in RAW? Can you run us through the typical processing for one your shots? For example, what specific tools do you use for noise reduction, sharpening, etc? As others have mentioned, are you sure your shots are actually properly focused with such a wide aperture?

[jdepould]

It's probably a combination of factors. Shooting up at ISO3200 can reduce acuity, and de-noising can soften things further. I generally don't shoot my D300 (crop sensor) that high, but my D700 (full frame) does fine up there.

If you're wide open, you've got extremely shallow DoF, and if your focus isn't perfect, things can appear soft.

That particular lens is more or less designed to operate at f/2.8. Shooting at f/5.6 will probably get you better MTF charts, but in practice the difference isn't as big as you might think.

[Fotoman!]

Thanks all for your responses. I have been swamped at work and have not been able to get over to my true love... photography... to be able to respond back.

The information is very helpful. It is great to have expert advise at hand. Let me check out your recommendations.

[rediguana]

A few other things in addition to what others have said here already:

1. The 7D may be slightly front/back focusing.
You could try testing the camera/lens combo and dialing in some micro-adjustments

2. The 70-200 may not be the sharpest lens.
That is a result of the compromises to have a zoom. Depending on what focal length you shoot the most at, it might be worthwhile renting/borrowing an 85f1.8, 100f2 or 135f2 - although I recognise that this may not be appropriate. These may give multiple benefits:
* faster AF
* sharper images than a zoom
* allow a higher shutter speed from the additional 1-1 1/3 stops.
You have to go prime if you want a lens >f2.8.

3. 18MP is harder to get truly sharp images.
This is something I'm still learning with my 7D. The increased resolution of the 7D at 18MP means it is actually more demanding on critical focus if you view at 100%. I'm finding that I'm generally having to improve my technique to get sharp 18MP images - as a simple result of the fact that 18MP contains nearly twice as much info as say a 10MP camera - and 18MP more willingly 'shows' camera or subject movement than a 10MP camera. Quite simply the increased resolution means there is less room for error.

[Fotoman!]

Thanks so much for taking time to respond! Great information.