Tilt Shift 90mm Sharpness

[dcooper]

Hi there, please can I get your help.

I have the Tilt Shift 90mm which I use for Product and Still Life photography in a studio. I love the sharpness and clarity of the lens, and so far I haven't really used the tilt function that often.

A few weeks back I dropped the lens on my camera body, 6D, from a height of about 2 feet onto the carpet and the shift had shifted by 8 degrees. It may have hit a piece of metal lying around.
I have only started to use the lens again recently.

I generally shoot Jewellery as part of still life set up with studio lighting; so on a table, I might put the Jewellery on a tile, or fabric.
If I fill the frame with the shot and focus a third of the way up (perhaps focussing on a specific Jewel), without tilting or shifting I am noticing that the top edges of the image, are a little soft, at f16. This is only really noticeable at 1:1 preview in Lightroom. If I focus nearer the top third, the bottom of the image is slightly soft at 1:1.

The edges are sharper at f22, naturally.

My question is, is this normal for this lens with the conditions that I work in, and am I pixel peeping, expecting too much, or should the lens not display softness around the edges at f11 - f 18, 20, when doing this kind of tabletop studio work? Am I focussing on the right point?

I did not notice this before it was dropped, but maybe I wasn't looking for it, plus I was cropping the edges of the frame, to get the best composition. I have checked previous images and one is slightly soft around the top edge.

thank you for your help in advance.

D.

 

[Marsu42]

If I fill the frame with the shot and focus a third of the way up (perhaps focussing on a specific Jewel), without tilting or shifting I am noticing that the top edges of the image, are a little soft, at f16.

This lens should be as sharp as they come, and if one side of the lens differs from the other side (try shooting a test chart) this points to decentering.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=349&Camera=453&Sample=0&FLI=0&API=6&LensComp=674&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=6

Am I focussing on the right point?

Do yourself a favor and use Magic Lantern - with focus peaking, you see exactly what is in focus and what isn't. And use focus stacking instead of diffraction at f22, will ya ?

 

[dcooper]

Thanks for your help. I will definitely look at Magic Lantern. I have heard of it, but didn't know what it was, until now.

I just looked up 'Decentering' and I am not sure if this applies to my issue. Forgive my inexperience, but when I say that the edges are soft I wonder if this is simply a Depth of Field issue, because the top portion of the image is out of focus? At f16 should the whole image be in focus from front to back?
This image is not parallel to the subject, does this make a difference?


Anyway I have enclosed an example jpeg.

D


The second image is an almost parallel to the subject photograph, and at f16, the corners are alot sharper, with some feint softness at the very edges. At f22, it is sharper still.
Is the issue still decentering, or is it the position of the camera?

Thanks,

D.

 

[Marsu42]

Is the issue still decentering, or is it the position of the camera?

Sorry if I've mis-understood you, decentering is really when one edge/side is different than the other(s). If you want to really test your lens, there's no way 'round printing and shooting a test chart.

At f16 should the whole image be in focus from front to back?

Hahaaha, no way, calculate to see the average depth of field (for a standard print/view size): http://www.dofmaster.com/dofjs.html

Forgive my inexperience, but when I say that the edges are soft I wonder if this is simply a Depth of Field issue, because the top portion of the image is out of focus?

Sure, that's why you do focus stacking, you cannot get infinite dof es. at close distance no matter how small the aperture. Or try f222 instead of just f22 :->

 

[dcooper]

Thank you for your help. My questions have been answered.