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Author Topic: Some observations on Leica M tests  (Read 3706 times)

ErikKaffehr

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Some observations on Leica M tests
« on: April 20, 2013, 02:21:22 am »

Hi,


I always find it is good to take all tests with a grain of salt. Lot's have been written about the new Leica M, here are some observations:


Erwin Puts who is famous for his Leica tests has published some observations which are erroneous.

1) http://www.imx.nl/photo/blog-2/lens-test-or-system-test.html

Here he states that Lloyd Chambers has overestimated focus shift on by a factor of 2500. Mr Chambers reported a focus shift of 20 mm at 1.8m while Erwin Puts has measured 0.008 mm on the optical bench. What Mr Puts misses is that Lloyd is discussing focus shift in the subject plane while he has measured the focus shift in the image plane.

Let's look at the lens equation that says: 1/f = 1/a + 1/b with a being distance from lens to subject a b being distance to from lens to film. So for a 50 mm lens focused at 1.8 m we would get b=1/(1/f - 1/a)) -> 51.42857 mm, with 2 cm focus shift we would get 51.41243, that is the focusing error would be 0.016 mm.

This is twice the amount measured that was measured on the optical bench by Mr. Puts. Pretty decent estimate.

I found no way to contact Erwin Puts to point out the mistake.

2) In the article below the writing is not very clear, but the edge contrast curves show a clear indication of sharpening:

http://www.imx.nl/photo/leica/leica-m-part-2-comparison.html




The reason that the program (Imatest?) gives MTF above 100% is neither the program nor the sharpness of the lens but the sharpening in raw conversion. That said, the is the lens is excellent, in all probability, but it is hard to deduce from the article as it is not clear how much of the measured MTF is attributable to sharpening, which sharpening parameters were used and it is not always clear what each curve shows.


3) Tim Ashley has tested the M (240) with a Summilux 35/1.4 FLE comparing it to Sony RX1, his finding was that the Summilux was tricky with a wavy field curvature. Tim's article is here: http://tashley1.zenfolio.com/blog/2013/4/leica-m-240-with-35mm-f1-4-fle---some-observations.


Leica: http://tashley1.zenfolio.com/img/s8/v76/p1528541534.jpg

Zeiss: http://tashley1.zenfolio.com/img/s8/v74/p1528544446.jpg

The above images are worth a look, the red labels slightly of axis in the Leica image are clearly out of focus while the text under "winners" is sharp.
 
4) Getting back to Mark Dubovoy's test, i have some observations:

- He uses camera white balance. Having a nice WB from a camera is certainly helpful, but in many situations a correct WB can be meassured using a grey card.

- An image with colder balance is generally perceived sharper.

- Making large size prints and using observers unaware of print identity is a good technique to compare images, but it is essential to keep processing out of the equation. Including a color checker and use for grey balance and exposure/contrast adjustment is a good way to compare images.

- Mark indicated that the Nikon exposes less to the right by default, that means that DR is not fully utilised. For complete utilisation of DR ETTR is essential. Most testers found that the M is somewhat more noisy in the shadows, but Mark's observations go into another direction.

Best regards
Erik
« Last Edit: April 20, 2013, 03:36:52 am by ErikKaffehr »
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Erik Kaffehr
 

Hulyss

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Re: Some observations on Leica M tests
« Reply #1 on: April 20, 2013, 02:57:52 am »

Mr Chambers also reported that I'm not professional and that there is no colour difference, at all, between the 3 DPs Merrill... witch is simply ... wrong. I think the best review ever should be a review done by a machine managed by a robot, not a human.

I mean, I have hard time to see were those hundred lines of blabla and numbers can help, in any possible way, the art of photography or just the photography :D without speaking about art at first :)

I respect ppl passions but those ppl are either bored or paid (and I sincerely hope this is the last option...).

Happy Saturday and lets pray for our Boston's friends.
« Last Edit: April 20, 2013, 08:38:47 am by Hulyss »
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ErikKaffehr

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Re: Some observations on Leica M tests
« Reply #2 on: April 20, 2013, 08:17:22 am »

Hi,

I don't know about DP Merills...

Regarding reviews, I know that Lloyd has it as a business. Tim is just sharing his experience. Erwin Puts seems to be involved with Leica in some way.

Anyway, I'm most thankful for reviewers sharing their experience. With a Leica, for instance, it would be horribly expensive to find out. The reviewers tend to put things in perspective. They also have experience of a lot of different systems.

Information is generally seen a good thing. There is also bad information and disinformation.

Best regards
Erik

Mr Chambers also reported that I'm not professional and that there is no colour difference, at all, between the 3 DPs Merrill... witch is simply ... wrong. I think the best review ever should be a review done by a machine managed by a robot, not a human.

I mean, I have hard time to see were those hundred lines of blabla and numbers can help, in any possible way, the art of photography or just the photography :D without speaking about art at first :)

I respect ppl passions but those ppl are either bored or paid (and I sincerely hope this is the last option...).

Happy Saturday and lets pray for your Boston's friends.
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Hulyss

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Re: Some observations on Leica M tests
« Reply #3 on: April 20, 2013, 08:38:28 am »

I still think that the best way to find out about a product is to test it by himself or trying to know someone who have the product. Then you are sure it is not money orientated ... but this is just my opinion, of course  :)
« Last Edit: April 20, 2013, 08:57:19 am by Hulyss »
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BrianVS

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Re: Some observations on Leica M tests
« Reply #4 on: April 20, 2013, 09:35:27 am »

Focus shift is typically reported in terms of shift at the image plane, as listed by Erwin Puts and most every test I've read over the last 40 years. I am surprised that anyone would list it as 20mm at 1.8m. Perhaps it was more of a "dig" than a misinterpretation of the report. I've seen lenses that required a 3mm change in he shim to correct the focus. But 20mm, would not be able to get te optics back into the focus mount.
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ErikKaffehr

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Re: Some observations on Leica M tests
« Reply #5 on: April 20, 2013, 10:20:37 am »

Hi,

With the Leica it's about 15K$, camera plus a couple of lenses, so I prefer someone else to do the testing.

Best regards
Erik

I still think that the best way to find out about a product is to test it by himself or trying to know someone who have the product. Then you are sure it is not money orientated ... but this is just my opinion, of course  :)
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ErikKaffehr

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Re: Some observations on Leica M tests
« Reply #6 on: April 20, 2013, 10:26:36 am »

Hi,

Diglloyd found that focus changes two centimetres in subject distance, that is he needs to move camera two centimetres to hold focus when stopping down, as said, it corresponds to 16 microns in the image plane.

By the way, I think that Erwin said before that lens to focal plane tolerance on the Leica M9 was 0.03 mm, 30 microns. So what Diglloyd reported is well inside normal tolerances for M9.

I think the sloppiness is on Erwin's part.

Best regards
Erik


Focus shift is typically reported in terms of shift at the image plane, as listed by Erwin Puts and most every test I've read over the last 40 years. I am surprised that anyone would list it as 20mm at 1.8m. Perhaps it was more of a "dig" than a misinterpretation of the report. I've seen lenses that required a 3mm change in he shim to correct the focus. But 20mm, would not be able to get te optics back into the focus mount.
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Erik Kaffehr
 

Telecaster

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Re: Some observations on Leica M tests
« Reply #7 on: April 20, 2013, 04:42:21 pm »

Hi,

With the Leica it's about 15K$, camera plus a couple of lenses, so I prefer someone else to do the testing.

Best regards
Erik

Here's how I intend to "burn in" my M240 when it arrives: strap on my rigid 50mm Summicron (c. 1965) and take a boatload of photos under varying conditions over a period of days or even weeks. If I get great results with that lens, whose characteristics I know like the back of my hand, I'll be confident in the camera's capabilities with every other M lens I own. If I don't get great results, I'll either return the camera or sell it on.

-Dave-
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Iluvmycam

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Re: Some observations on Leica M tests
« Reply #8 on: April 20, 2013, 05:38:06 pm »

Does anyone just have some good comparison pix?
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