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Kim Dahl

FF Lens on APS-C camera and APSC on FF camera

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This is a very academic discussion, he said it, if you are happy with your results use the lens. He was using cameras with AA filters and basically made a blanket statement that all cameras have AA filters. Leica Ms and the CL don't have AA filters, not sure about the SL/SL2 but if Leica is consistent it doesn't. Another comment was the better the lens the less difference between full frame and APS-C sensors, so you buy a Leica why? To get the best optics around. As I said it is an academic discussion.

There are many people on this forum using M lenses on a CL/TL and liking the experience. So if you have a CL/TL and like your images why change? Especially with the weight differences. If you want to go up another step, I would go with an M10 rather than a SL/SL2 but that is me, the SL2 just looks like a beast to me. I also have used M cameras for years and have no experience with the SL/SL2.

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Okay, so I watched part of the video (as much as I could stand). He takes some zoom lens, sets it at one focal length to get a particular framing on FF, then sets it on an APS-C camera and selects a different focal length to get the same framing there. Uh, duh: Do you want to assume that a zoom lens has exactly the same optical performance at every focal length setting? Really? That's a completely ridiculous notion. 

How a given lens performs with a given sensor has to do with a) the size of the sensor, b) the quality of the sensor's AA filtration, and c) the performance of the lens at some specific focal length. If you're trying to measure resolution at the corners and edges of the frame between a FF and an APS-C format camera, the only sensible way to do this is to use a resolution chart and place the resolution test section you want to use as the basis of your measurement at the various locations in the field of view of that lens on whichever sensor you want to test. You leave the focal length of a zoom lens (and the aperture, etc) locked to the same values. Then differences in the sharpness will be attributable to how good an optical match there is between the lens and that particular sensor stack. BTW, you can't just test two sensors and generalize from that test that all uses of said lens on all FF size sensors vs APS-C sensor will perform the same either, since the sensor stack varies even between different sensors of the same dimensions based on what the manufacturer had in mind in tuning the sensor performance for their lenses and uses. 

This video is a typical example of the kind of ill-thought-out testing and suspect conclusions that are rife on YouTube. That's all. :D

G

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3 hours ago, cdekter said:

He literally addressed all those concerns at the end of the video. Watch it all the way to the end did you?

I had my fill of the horsepucky at about minute two. :)

 

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6 hours ago, cdekter said:

He literally addressed all those concerns at the end of the video. Watch it all the way to the end did you?

Doing everything wrong is not corrected by apologizing at the end.

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Why so harsh? Its not only Tony Northrup pretending this. DXOMark comes to the same results. And note that Tony clearly states that the better the lens the smaller the differences. So please be careful what you think is fake news. By the way Tony has other videos assigned to this subject. He does not just use Zoom lenses. 

Dxomark created the term "perceptual megapixels" to explain this. But it gets somehow difficult when some think that Dxomark is rubbish as well. Then the discussion itself becomes nonsense. 

Edited by M10 for me

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I have no clue about "perceptual megapixels" but using a zoom lens at different focal lengths is as useless as using different lenses for such comparisons. I might also compare a TE 28-35-50 at 50mm on M240 to the same lens at 35mm on digital CL. What would i learn this way? That the lens flares more at 50mm to conclude that FF is more prone to flare than APS-C?

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DXOmark is mostly rubbish too. Sorry.

"Perceptual megapixels"? Point me to an ISO standard for such things and I'll begin to take them seriously. :)

G

"The problem with standards is that there are so many of them."

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well, no need to make fun about something you never heard about. This forum should not be an echo chamber. You'll find out that you can really measure these things.

I think though that there is another thing that is important. The differences are measurable but very small.

Edited by M10 for me

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3 minutes ago, M10 for me said:

well, no need to make fun about something you never heard about. This forum should not be an echo chamber.

Oh I heard about them ages ago. I looked into what they were trying to say. It made no sense then, and it makes no sense now. I've never seen a single bit of value in any of the various "DXO marks" and standards that made a difference to either my photography or to the evaluation of my cameras' results. Not one. 

I'm not making fun of them at all. I'm saying that they are without value. Except maybe to foolish reviewers who, not understanding anything themselves, seek credibility for their ridiculous notions by referring to other foolish reviewers who get good ratings on YouTube.

G

Edited by ramarren

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If you're trying to say "things that you can measure always make sense", I wonder just what the point of that statement is. What have you measured? What has this reviewer measured?

The inferences drawn from appropriate measurement are the critical part of evaluation. Saying, "There are 100,217 telephone poles on I-70 in Kansas and there are 510,437 telephone poles on I-266 in Alaska" are a statements of measure. To then say "Telephone poles in Alaska are more populous than in Kansas" in the absence of any other data Is an absurd inference from those two data points. 

But he didn't even present a measurement. He just said one of the images made was sharper than the other. It wasn't a resolution test chart or anything that implied measurement. 

Just bonkers.

G

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