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03-15-2014, 08:07 AM   #1
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CROP or TC - which is best

The following pictures were taken with a K-3 and Sigma 500 4.5 lens. These were very small sections of each photo, cropped to be about the same size. The sequence was mixed so #1 of one shot may or may not be the same focal length as #1 of another shot.

So can you pick the photos taken with just the 500 versus those taken with the 500 and Sigma 1.4 TC?

What's your verdict - crop versus no crop.

I will post the results tomorrow or the next day depending on replies.

I did try to make things fair by using a ColorChecker to calibrate both lens configurations in the same light, when theses shots were taken, and applying a lens calibration to each raw image. That was the only processing done other than cropping.

After posting I have no idea why one lamp is larger than the other. The rest are the same size?

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03-15-2014, 08:57 AM   #2
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On the car I say #1 is TC due to visible CA

On lamps I have no idea

On plant I say #2 is TC due to higher ISO needed for equal exposure causing more grain

On tree I say #2 is TC as seems less cropping needed

I could be totally off so to be sure please send me your 500 so I can run my own tests
03-15-2014, 10:22 AM   #3
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Licence plate 1 is TC, 2 is crop (more CA in 1 and more noise in 2).
Lamps...?
Leaves, 1 is crop and 2 is TC (more noise and deeper DOF).
Notice, 1 is OOF and 2 is TC (noise).
03-15-2014, 10:27 AM   #4
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I think the first one of each pair is crop, second Tc.

03-15-2014, 10:37 AM   #5
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in general my experience with teleconveters has been the following:
  • Lens wide open: if given a choice, it is better to crop
  • Lens stopped down: if given a choice, it is better to use TC

YMMV
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03-15-2014, 11:19 AM   #6
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You say these were very small sections of each photo. To judge things I'd like to see the full image because small crops exaggerate differences in sharpness and CA, and decrease differences in contrast and color. Some lenses that give good pixel peeping results are not so good when printing larger sizes.

Photo 1 car: 2nd image looks better. The small Reynolds & Reynolds text in the lower right is noticably sharper. The emblem at the top is a bit blown out in both examples, but has better contrast in the 2nd image and shows less CA. #1 is TC?

Photo 2 lamp: The 2nd looks like a better exposure but it's tough to to tell with the different sizes. The 1st image shows more reflection off the outer light fixture glass; that might be due to changing cloud conditions rather than optical differences.

Photo 3 plant: 1st image is better. Better focus or maybe better detail retention. The 2nd image is considerably noisier despite being dimmer; the 1st looks a tiny bit overexposed but that's easily fixed. #2 is TC?

Photo 4 label on tree: 2nd image is better. Much sharper. #1 is TC?
03-15-2014, 12:05 PM   #7
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TC is:

Car: #1
Lamp: #2
Plant: #2
Tree: #1? - either way #1 is OOF


EDIT: OK, so on the Tree #2 is the TC. Even though I could see the evidence, I just didn't want to admit it because of the OOF 1st shot.

Last edited by DSims; 03-15-2014 at 11:58 PM.
03-15-2014, 01:36 PM   #8
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Original Poster
QuoteOriginally posted by DeadJohn Quote
You say these were very small sections of each photo. To judge things I'd like to see the full image because small crops exaggerate differences in sharpness and CA, and decrease differences in contrast and color. Some lenses that give good pixel peeping results are not so good when printing larger sizes.

Photo 1 car: 2nd image looks better. The small Reynolds & Reynolds text in the lower right is noticably sharper. The emblem at the top is a bit blown out in both examples, but has better contrast in the 2nd image and shows less CA. #1 is TC?

Photo 2 lamp: The 2nd looks like a better exposure but it's tough to to tell with the different sizes. The 1st image shows more reflection off the outer light fixture glass; that might be due to changing cloud conditions rather than optical differences.

Photo 3 plant: 1st image is better. Better focus or maybe better detail retention. The 2nd image is considerably noisier despite being dimmer; the 1st looks a tiny bit overexposed but that's easily fixed. #2 is TC?

Photo 4 label on tree: 2nd image is better. Much sharper. #1 is TC?
Here are the original pictures

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03-15-2014, 03:31 PM   #9
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I would guess 2 is cropped on all pictures
03-15-2014, 05:03 PM   #10
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In general using a TC will degrade image quality. About the only two exceptions are #1- if the lens manufacturer has designed a specific lens and a specific TC as a matched set. So far I have yet to see the combined price for such a matched set as less than a lens of similar quality at the longer focal length. #2- extreme enlargements. Here if you crop, noise (or grain) will also be enlarged and often be more noticeable than the hit on IQ from the TC.
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