Quick 28-75XRDi f2.8-f6.3 Comparison

[dsze]

I had always felt that I've gotten sharp images wide open with my Tamron 28-75, and wondered if all the talk about it being soft wide open was really that it was soft or just some folks interpreting a very shallow DOF as softness. Here's a very NON-SCIENTIFIC comparison of f2.8/f6.3. This isn't meant to conclude anything at all, but it is somewhat of a 'real-life' type of shot that one might be interested in. These were shot RAW A.RGB, are straight out of camera with zero processeing. To me, the wide open image does look softer, but still not bad in my opinion.

http://home.comcast.net/~randomphotos/tamron2875/CRW_7861.jpg
http://home.comcast.net/~randomphotos/tamron2875/CRW_7860.jpg

-daniel

[willg]

yeah obvsiously softer but not anything extreme

[dsze]

yeah obvsiously softer but not anything extreme


...agreed. And keeping in mind that this is with no in-camera and no post sharpening at all. With a little sharpening in the RAW conversion and/or USM in PS, the f/2.8 is very usable.

-daniel

[DavidEB]

The purple flower is a 3-D object and probably doesn't fall entirely within the depth-of-field at f2.8. Because the flower is uniform in color it's hard to tell where the plane of focus is.

Look at the closed bud at top (the green thing with maybe thorns or spikes on it). In the f2.8 shot you can clearly see how narrow the depth-of-field is, and you can also see that for those spikes which are in focus, there's not a lot of difference between the f2.8 and f6.3

I can tell the difference on mine between f2.8 and f4 or above but only if I set up the shot very carefully. Much of the OOF areas are just due to the very shallow DOF of this lens especially at longer focal lengths.

not convinced, sorry....

[dsze]

The purple flower is a 3-D object and probably doesn't fall entirely within the depth-of-field at f2.8. Because the flower is uniform in color it's hard to tell where the plane of focus is.

Look at the closed bud at top (the green thing with maybe thorns or spikes on it). In the f2.8 shot you can clearly see how narrow the depth-of-field is, and you can also see that for those spikes which are in focus, there's not a lot of difference between the f2.8 and f6.3

I can tell the difference on mine between f2.8 and f4 or above but only if I set up the shot very carefully. Much of the OOF areas are just due to the very shallow DOF of this lens especially at longer focal lengths.

not convinced, sorry....

Thats, my point. I believe this issue to be largely due to many people incorrectly calling shallow DOF, softness at f/2.8. However, you can clearly tell that the very center of the flower (where the focus point was), is not as sharp in the f/2.8 image. Its close, and its certainly not "bad" but it is a little softer, which I guess would be expected with any lens.

-daniel