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As I was recommended in the question How to determine which lenses are good at testing teleconverter quality? I was taking test pictures trying to determine lens/teleconverter quality. No I did not have a proper test chart available but figured the bar-code on a box I had laying around would get me partway there.

Attaching 2 1-1 crops from my tests, I am correcting colorcast and color fringing when doing raw conversion in Digikam. The first image is the bare lens the second is using the Kenko Pro300 3X Teleconverter.

Test shots taken with a Canon 5D Mark II and an adapter SMC Pentax-M 135mm f3.5.

  • Focus: Manual
  • Mode: Aperture Priority
  • Remote Trigger: Yes
  • Tripod: Yes
  • Mirror lockup: No (will use this when re-shooting)

enter image description here enter image description here

As can be seen neither image is sharp when pixel-peeping at this level but if anything the second image (with tele-converter) is even less sharp, unsurprisingly.

What are the optical problems in these images, can they be identified from the attached files? Is it just me missing focus? Is it the anti-aliasing fitted in the camera? Is it the quality of the lens (would a better lens be sharper with the rest of the setup the same)?

More test images based on comments

Two more test images with updated settings based on comments, the first one is without TC and the second one is with, cropped from in camera JPG.

  • Focus: Manual
  • Mode: Aperture Priority
  • Remote Trigger: Yes
  • Tripod: Yes
  • Mirror lockup: Yes
  • Picture Style: Standard (sharpness 4)
  • White-balance: Tungsten
  • Aperture: F8
  • Exposure: 20 seconds with TC, 3.2 seconds without
  • ISO: 100

enter image description hereenter image description here

In the process of shooting these the most surprising improvement was mirror lockup, there is still some fussiness but the tips applied have it much reduced for both configurations.

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  • Can you retake the images? Use full manual mode and increase exposure so that the "white" will be more white. If possible, focus using tethering and magnification. You'll also have to compensate for lost light when using the TC. Also, use sharpness +1 to counteract the effects of the anti-aliasing filter. Otherwise your images will never look sharp when pixel peeping.
    – xiota
    Jan 21, 2020 at 20:54
  • Yes I can, so full manual and experiment until the white is more white and no empty part of histogram? Is the +1 sharpness the sharpness in the canon in camera picture styles? it was set to 3, would setting it to 4 do or should I go further? Will experiment with these settings now.
    – lijat
    Jan 21, 2020 at 21:00
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    The first image from the retake is more like what I'd expect from a Pentax lens (but now looks over sharpened). Without measuring lpmm, I don't know how to tell from these images the contribution of the TC vs magnification.
    – xiota
    Jan 21, 2020 at 21:41
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    CA is pretty typical when old lenses are used wide open. Stopping down just a fraction of a stop is usually enough to fix it. It's going to be tough to test with your camera because of difficulty manual focusing and the AA filter. Here is an image that demonstrates the effects of AA filter on sharpness.
    – xiota
    Jan 21, 2020 at 22:12
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    It seems like you're just asking why you aren't getting sharp images with the lens on your camera. If so, all of your hypotheses are possible, and you just need to systematically rule each one out. See also, Why are my photos not crisp?
    – xiota
    Jan 22, 2020 at 4:37

1 Answer 1

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Just a crop at the center of the picture doesn't show possible problems of vignetting, additional softness on the edges, and distortion. The images aren't very well exposed either and this reduces contrast.

There are a few things to check if you want to make sharp pictures,especially with long focal lenses:

  • shooting speed
  • use of tripod
  • remote trigger
  • mirror lockup

Not knowing what you did makes it difficult to give an answer.

Also, I assume the autofocus was disabled, so how did you set the focus?

Improve this answer
6
  • When you say they are not well exposed, I shot them using aparture priority with the exposure compensation in the middle somewhere. If I want to get it set perfectly for maximum contrast how do I achive that? Is there som certain way the histogram should look? Or how do I determin what is correct?
    – lijat
    Jan 21, 2020 at 20:43
  • I am not that worried about bad quality near the edges, I am more focused on trying to identify the cause of the fussiness in the center.
    – lijat
    Jan 21, 2020 at 20:44
  • The white should be a lot whiter. The histogram of your pictures is very much to the left.
    – xenoid
    Jan 21, 2020 at 20:45
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    See edited answer... whih starts to look like a question :)
    – xenoid
    Jan 21, 2020 at 20:47
  • I was using tripod and remote trigger but not mirror lockup. I was shooting in aperture priority. Will edit this into the question. And try with mirror lockup
    – lijat
    Jan 21, 2020 at 21:02

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