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Telecentric lenses and microlens arrays


bencoyote

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My opinion is that people buy Leica lenses for their superlative performance across the frame. Then suddenly you put your cron 28 on the a7 and it performs like a Coke bottle bottom in the frame periphery. Then you put it on the SL and it performs much better, like a 250$ Japanese lens from film days. I would think the quality is acceptable, or not, depending on what you expect.

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How many times do we need sharp corners actually? I'm using currently a tiny kit i like much with Fuji X-E2, Leica 35/2.5, 50/2.5 & 21/3.4, all this stuffed in my 30+ y/o combi case for Leica CL. The 21/3.4 is superb but when i focus at infinity, i get soft corners below f/8. Does it make it a dud for that? I don't think so. Anyway, all Leica lenses are not M's are they. The SL should work fine with R lenses hopefully failing which i will forget it definitely.

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How many times do we need sharp corners actually? I'm using currently a tiny kit i like much with Fuji X-E2, Leica 35/2.5, 50/2.5 & 21/3.4, all this stuffed in my 30+ y/o combi case for Leica CL. The 21/3.4 is superb but when i focus at infinity, i get soft corners below f/8. Does it make it a dud for that? I don't think so. Anyway, all Leica lenses are not M's are they. The SL should work fine with R lenses hopefully failing which i will forget it definitely.

That was exactly my point. The 21/2.4 that you can use wide open for landscapes on your M needs to be stopped down to f/8 on the new SL. Whether this is acceptable or not, only you can say. On the good side, shooting wide open at close range will actually enhance the out of focus blur, so I know some photographers who would actually like that aspect.

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I've put in some time using the minimally acceptable VF-2 EVF with my M[240] and both long teles and the Leica 21/3.4 and 18/3.8.  For the R telephotos and the nice Elmarit-R 60 macro, the SL is a big win.  I have the Leica R to M adapter (and a coded Novoflex), and the M to T is easily available.  I won't have to wait for the R to T adapter from Leica, so my order is in.  

 

Using the SL with the extreme wides should be interesting...  On the M[240] I can see an improvement with the SE 21 when stopping down from 3.4 to about 5.6, but it has never occurred to me to go beyond that point.  And I'm not sure that any viewfinder can tell me all the interesting things that can pop up in a super wide angle shot, once I render the file that results.

 

Can't see any good reason to work with 28, 35, and 50 mm lenses on anything but an M[240].

 

scott

Edited by scott kirkpatrick
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Sounds like the 28 Summilux is not a challenging "compact wide" and works well with the SL.  

 

When is comes down to it, Sean and Jono are the ones who have taken the time to do the testing (which I won't). Their findings are good enough for me, and certainly better than contrary opinions based on ... actually, I'm not sure what they're based on.  Pessimism?

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  • 2 weeks later...

Ben, 

 

Could you provide links where it is asserted that the SL lenses are (will be) telecentric? I'd like to improve my understanding of the topic.

 

If these lenses are telecentric, then I need to change my understanding of what that means, because what I saw yesterday made me think that isn't the case: I had a look at the Vario-Elmarit-SL 24-90mm in person and it struck me that the rear element was less that 43mm in diameter. In fact, putting a ruler on Leica's data sheet, it looks like the diameter of the rear element is something like 23mm. Doesn't that imply that the lens can't be image space telecentric, given that the image circle is 43mm in diameter? I'm thinking an image space telecentric lens has to have a rear element that is at least as big as the image circle.

 

That this lens is not object space telecentric is shown in the data sheet: the entrance pupil is at a position much closer than infinity.

 

dgktkr

 

 

...

 

Reading this forum and others, it seems that the reason that they are so big is that they are a telecentric design.

 

...

 

 

Edited by dgktkr
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This certainly has boiled up to a veritable vegetable quandary, once again.  Lettuce remember back in thyme a month ago with the leek of the SL.  We had no vegetable photos.  Now we are peppered with Sean's infamous vegetable photos.  Beets me why everyone now wants to talk about vegetables.  But, no amount of wishing that I never see a test photo of a vegetable will stop it, and that is how it has bean and no amount of wishing will squash it. ;)

 
All I want is an M-Pea... 
 
Rick
 
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What happens (crop ratio) when you attach a S lens to the SL body?

 

There is none. A 70mm lens will be a short tele with a 70mm field of view on the SL while it is a standard lens with a 56mm field of view on the S.

Edit: Haven't we discussed about this elsewhere? If so, please ignore my post above sorry.

Edited by lct
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Thank you, Michael.

 

 And do you know if the SL sensor has the same "shallow buckets" the M(240) sensor has, or the micro lenses the Kodak sensor on the M9 had?

 

 

 

I don’t know, but in any case the sensor was designed to cope with all kinds of lenses, both telecentric lenses and lenses where the exit pupil is close to the rear lens.

Hi There John, Michael

I understand that the microlenses on the SL have been designed in a similar way to the M240 ('shallow buckets').

 

The cover glass is slightly thicker than the M240, and the performance of the 'problem' M lenses (28 'cron etc) is slightly less good than it is on the M - but a great deal better than it is on the Sony A7 cameras which have a much thicker cover glass, normal micro-lenses and no vignetting correction.

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Hi There John, Michael

I understand that the microlenses on the SL have been designed in a similar way to the M240 ('shallow buckets').

 

The cover glass is slightly thicker than the M240, and the performance of the 'problem' M lenses (28 'cron etc) is slightly less good than it is on the M - but a great deal better than it is on the Sony A7 cameras which have a much thicker cover glass, normal micro-lenses and no vignetting correction.

 

Does this mean you found the color to be a little easier or better or different to work with than the M?  

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If these lenses are telecentric, then I need to change my understanding of what that means, because what I saw yesterday made me think that isn't the case: I had a look at the Vario-Elmarit-SL 24-90mm in person and it struck me that the rear element was less that 43mm in diameter. In fact, putting a ruler on Leica's data sheet, it looks like the diameter of the rear element is something like 23mm. Doesn't that imply that the lens can't be image space telecentric, given that the image circle is 43mm in diameter? I'm thinking an image space telecentric lens has to have a rear element that is at least as big as the image circle.

Even Olympus who were the first to stress the importance of near telecentric lenses with image sensors never claimed the lenses needed to be strictly (image space) telecentric. ‘Near telecentric’ is not a well-defined term but for all intents and purposes it means that the exit pupil is far enough from the sensor so as not to create issues with large incident angles. The SL standard zoom fits that description.

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Michael,

 

Do you know the distance between the sensor of the SL and the exit pupil of the standard zoom ?

 

dgktkr

 

... ‘Near telecentric’ is not a well-defined term but for all intents and purposes it means that the exit pupil is far enough from the sensor so as not to create issues with large incident angles. The SL standard zoom fits that description.

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Do you know the distance between the sensor of the SL and the exit pupil of the standard zoom ?

I would have to guess – maybe about 70 mm at the wide end, more at the tele end of the zoom range.

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