Pixel peepers wanted...

**othar** · 11-15-2021, 01:37 AM - **1 Like**

Originally posted by Lloyd_Christmas

decentering best evaluated with max aperture which for this lens is f2.8???

Misalignments are in my opinion easiest spotted when shooting wide open, yes.

This can be done with a brickwall test (or a similar subject) as have already been suggested, the difficulty thereby is to perfectly align the camera with the subject though.
Because of that I find it more convenient to use the horizon (preferably with some trees or other details in it)for a quick test; place it in the centre of the image -> focus manually (with LV; on a tripod) to exclude focus errors -> take an image -> rearrange the horizon (but leave the focus untouched) to the top and bottom of the image and take 2 more images.
Compare the image quality of the edges and borders of the 3 images -> I don't know this lens from first hand experience, but there might be some field curvature visible; slightly blurry edges might be normal wide open, therefore you are looking for edges that are more blurry (and have more chromatic aberrations) than the others.
Decentering is also a bigger problem with wide angle lenses, therefore I'd suggest doing this at least for the 16mm focal range, but additional tests for 35mm and 50mm might also be of interest.

**ehrwien** · 11-20-2021, 02:18 PM - **1 Like**

Originally posted by biz-engineer

You get the kind of sharpness that is expected from an APSC format camera. The sensor is no larger 16x24mm, prints no larger than 16"x24" should be fine.

I have just had a print in 23"x31" made from a third of the K-3III's full resolution and it looks great.

tibbitts · 11-21-2021, 03:13 PM - **1 Like**

Originally posted by Lloyd_Christmas

What do you think?

Speaking as someone who assumes a high percentage of lenses are decentered to an unacceptable degree, the first photo looks very good, especially for having been made with probably the least-highly-regarded DA* lens (I'm assuming this is the original, not the new 16-50 version?) However you should really do more controlled tests following the suggestions that have already been made, so you won't have any regrets later, once your exchange period is over.

Lloyd_Christmas · 11-21-2021, 06:31 PM

Originally posted by tibbitts

Speaking as someone who assumes a high percentage of lenses are decentered to an unacceptable degree, the first photo looks very good, especially for having been made with probably the least-highly-regarded DA* lens (I'm assuming this is the original, not the new 16-50 version?) However you should really do more controlled tests following the suggestions that have already been made, so you won't have any regrets later, once your exchange period is over.

Thanks for the advice. It is the new DA* 16-50.
I did some shots of a wall and used a tripod. Looks like the lens is a good one...at least from what I could see.
My 30 day return period from Ricoh is over soon but I plan to keep the lens.

Check out this shot that shows a little bit of what it can do coupled with the K-3 mkIII

Untitled | Vince Mokry | Flickr

**mikesbike** · 11-21-2021, 10:07 PM

If you do such a test and it looks good, it is good. Another test I do against possible decentered is to pick out a solid subject with detail. Perhaps a street lamp. I shoot wide open. First I shoot with the subject centered and using center-only spot focus. When I know it is a perfectly-focused shot, I switch to MF so the focus does not wander for any reason. Then I reposition the camera, doing shots placing the subject at different locations in the frame, like right border, left border, top, bottom, corners, etc. and knowing the center shot will reflect highest quality, but the difference in quality compared to the center is to be the same side to side, top to bottom. If the lens is exceptional, there will still be good sharpness even at frame edges when wide open. But your brick wall test is a good one too, at various FLs, if set up well.

tibbitts · 11-21-2021, 10:10 PM

Originally posted by Lloyd_Christmas

Thanks for the advice. It is the new DA* 16-50.
I did some shots of a wall and used a tripod. Looks like the lens is a good one...at least from what I could see.
My 30 day return period from Ricoh is over soon but I plan to keep the lens.

Check out this shot that shows a little bit of what it can do coupled with the K-3 mkIII

Untitled | Vince Mokry | Flickr

Ah... yes I don't have one but would guess the new version is an improvement in optics, not just focusing speed and durability. I only have the Sigma 17-50 and am very happy with that for what I paid (pre-owned), although PDAF at wider apertures isn't accurate for me.

Lev · 11-21-2021, 11:04 PM - **1 Like**

When I'm getting a new lens my first to-do is to check wether or not it is decentered. Then some tests for sharpening. I usualy need two test charts, Siemens Star for decentering, and ISO 12233 for sharpness tests. But taking test images require lots of rules to be followed.

tibbitts · 11-23-2021, 07:33 PM

Originally posted by mikesbike

If you do such a test and it looks good, it is good. Another test I do against possible decentered is to pick out a solid subject with detail. Perhaps a street lamp. I shoot wide open. First I shoot with the subject centered and using center-only spot focus. When I know it is a perfectly-focused shot, I switch to MF so the focus does not wander for any reason. Then I reposition the camera, doing shots placing the subject at different locations in the frame, like right border, left border, top, bottom, corners, etc. and knowing the center shot will reflect highest quality, but the difference in quality compared to the center is to be the same side to side, top to bottom. If the lens is exceptional, there will still be good sharpness even at frame edges when wide open. But your brick wall test is a good one too, at various FLs, if set up well.

I would suggest setting the exposure to manual so it won't change when you reframe. Generally my experience has been that images (or any part of them) look less sharp with more exposure (when lighter), and if not set to manual, exposure will vary as the image is reframed.

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11-15-2021, 01:37 AM - 1 Like	#16
othar Site Supporter Join Date: May 2014 Location: Linz Photos: Albums Posts: 3,098	Originally posted by Lloyd_Christmas decentering best evaluated with max aperture which for this lens is f2.8??? Misalignments are in my opinion easiest spotted when shooting wide open, yes. This can be done with a brickwall test (or a similar subject) as have already been suggested, the difficulty thereby is to perfectly align the camera with the subject though. Because of that I find it more convenient to use the horizon (preferably with some trees or other details in it)for a quick test; place it in the centre of the image -> focus manually (with LV; on a tripod) to exclude focus errors -> take an image -> rearrange the horizon (but leave the focus untouched) to the top and bottom of the image and take 2 more images. Compare the image quality of the edges and borders of the 3 images -> I don't know this lens from first hand experience, but there might be some field curvature visible; slightly blurry edges might be normal wide open, therefore you are looking for edges that are more blurry (and have more chromatic aberrations) than the others. Decentering is also a bigger problem with wide angle lenses, therefore I'd suggest doing this at least for the 16mm focal range, but additional tests for 35mm and 50mm might also be of interest.

11-20-2021, 02:18 PM - 1 Like	#17
ehrwien Site Supporter Join Date: May 2016 Posts: 2,784	Originally posted by biz-engineer You get the kind of sharpness that is expected from an APSC format camera. The sensor is no larger 16x24mm, prints no larger than 16"x24" should be fine. I have just had a print in 23"x31" made from a third of the K-3III's full resolution and it looks great.

11-21-2021, 03:13 PM - 1 Like	#18
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	Originally posted by Lloyd_Christmas What do you think? Speaking as someone who assumes a high percentage of lenses are decentered to an unacceptable degree, the first photo looks very good, especially for having been made with probably the least-highly-regarded DA* lens (I'm assuming this is the original, not the new 16-50 version?) However you should really do more controlled tests following the suggestions that have already been made, so you won't have any regrets later, once your exchange period is over.

11-21-2021, 06:31 PM	#19
Lloyd_Christmas Pentaxian Join Date: Jul 2013 Location: Atlanta, GA Posts: 462 Original Poster	Originally posted by tibbitts Speaking as someone who assumes a high percentage of lenses are decentered to an unacceptable degree, the first photo looks very good, especially for having been made with probably the least-highly-regarded DA* lens (I'm assuming this is the original, not the new 16-50 version?) However you should really do more controlled tests following the suggestions that have already been made, so you won't have any regrets later, once your exchange period is over. Thanks for the advice. It is the new DA* 16-50. I did some shots of a wall and used a tripod. Looks like the lens is a good one...at least from what I could see. My 30 day return period from Ricoh is over soon but I plan to keep the lens. Check out this shot that shows a little bit of what it can do coupled with the K-3 mkIII Untitled \| Vince Mokry \| Flickr

11-21-2021, 10:07 PM	#20
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,558	If you do such a test and it looks good, it is good. Another test I do against possible decentered is to pick out a solid subject with detail. Perhaps a street lamp. I shoot wide open. First I shoot with the subject centered and using center-only spot focus. When I know it is a perfectly-focused shot, I switch to MF so the focus does not wander for any reason. Then I reposition the camera, doing shots placing the subject at different locations in the frame, like right border, left border, top, bottom, corners, etc. and knowing the center shot will reflect highest quality, but the difference in quality compared to the center is to be the same side to side, top to bottom. If the lens is exceptional, there will still be good sharpness even at frame edges when wide open. But your brick wall test is a good one too, at various FLs, if set up well.

11-21-2021, 10:10 PM	#21
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	Originally posted by Lloyd_Christmas Thanks for the advice. It is the new DA* 16-50. I did some shots of a wall and used a tripod. Looks like the lens is a good one...at least from what I could see. My 30 day return period from Ricoh is over soon but I plan to keep the lens. Check out this shot that shows a little bit of what it can do coupled with the K-3 mkIII Untitled \| Vince Mokry \| Flickr Ah... yes I don't have one but would guess the new version is an improvement in optics, not just focusing speed and durability. I only have the Sigma 17-50 and am very happy with that for what I paid (pre-owned), although PDAF at wider apertures isn't accurate for me.

11-21-2021, 11:04 PM - 1 Like	#22
Lev Veteran Member Join Date: Aug 2015 Location: Tbilisi, Georgia Posts: 1,197	When I'm getting a new lens my first to-do is to check wether or not it is decentered. Then some tests for sharpening. I usualy need two test charts, Siemens Star for decentering, and ISO 12233 for sharpness tests. But taking test images require lots of rules to be followed.

11-23-2021, 07:33 PM	#23
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	Originally posted by mikesbike If you do such a test and it looks good, it is good. Another test I do against possible decentered is to pick out a solid subject with detail. Perhaps a street lamp. I shoot wide open. First I shoot with the subject centered and using center-only spot focus. When I know it is a perfectly-focused shot, I switch to MF so the focus does not wander for any reason. Then I reposition the camera, doing shots placing the subject at different locations in the frame, like right border, left border, top, bottom, corners, etc. and knowing the center shot will reflect highest quality, but the difference in quality compared to the center is to be the same side to side, top to bottom. If the lens is exceptional, there will still be good sharpness even at frame edges when wide open. But your brick wall test is a good one too, at various FLs, if set up well. I would suggest setting the exposure to manual so it won't change when you reframe. Generally my experience has been that images (or any part of them) look less sharp with more exposure (when lighter), and if not set to manual, exposure will vary as the image is reframed.