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21mm SEM corner performance


mirekti

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Sorry for bringing this up again, but I need to know whether I should send this lens for another replacement or it would be safer to send it to Leica for a repair.

In short, I got a 21mm SEM few weeks back, and it had smeared left corners. I asked the seller for a replacement, and yesterday I received a second copy. This one has the similar issue, maybe even stronger, but this time on the other side.

 

Do you think it is better to send the lens for a repair or ask for another replacement?

I'd rather send it to Leica to get it fixed once for all than possibly get another "bad" copy.

 

Is there a way to fix this at all? I mean, how can thay fix only one corner of the lens? I'm not so familiar with the inner looks of the barrel.

 

Here is a sample photo, lower left corner looks great (yet a first copy was a tad better in the corner which had no problems), but the upper right not so.

I also uploaded dng file if someone would like to take a closer look. https://www.dropbox.com/s/zkp5tdfx6nyua29/L1004913.dng

 

I believe Leica will check this, and I had great experience with their customer service/repair, but the whole situation with a new lens, two in a row, is really annoying.

 

Thanks!!

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Based on somewhat similar experience with WATE, I would think that the problem is a slight misalignment of one/several of the lens elements. It can be fixed, but requires accurate handling. My WATE is, as an example, going back to Solms for a second adjustment...

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Number 3 is not at the same distance from the centre of the image in all corners. This might be the reason in lenght difference. Even though I cannot completely exclude user error, I took a lot of care to get it as close as possible to ideal settings. The most important fact, corners remain similar even at f8-11, so I believe my error could be ruled out.

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once aligned, is it a permanent solution or your WATE misaligned again, hence, this second trip to Solms?

I don't quite understand the way elements inside are adjustable.

 

The lens was off in the first place. It was sent to Solms, adjusted and came back. The adjusted lens was still not good as demonstrated below (right section of a test photo). Therefore a new trip to Solms. And now I hope that the lens will behave as it is supposed to do...

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I'm not sure Leica wides are ideal lenses for obtaining a flat plane of focus. I don't have the 21 SEM but the two modern wides I do have – 28 Summicron and 35 FLE – have a focus plane that is all over the place.

 

I have both the 21 SEM and the 35 FLE. I agree with you that the FLE has a plane of focus that is all over the place but the SEM is much better in this respect and probably isn't bettered by any other Leica M lens in the 21mm to 16mm range.

 

I have to admit my first thought on seeing the OP's image was that it is very difficult to ensure the camera is aligned precisely. My next thought was to wonder if the OP was going to be photographing charts and if not then perhaps a better test of the lens would be testing on the subjects and at the distance and aperture that he would typically shoot.

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Number 3 is not at the same distance from the centre of the image in all corners. This might be the reason in lenght difference. Even though I cannot completely exclude user error, I took a lot of care to get it as close as possible to ideal settings. The most important fact, corners remain similar even at f8-11, so I believe my error could be ruled out.

 

If you are photographing a flat plane with a lens that has no distortion (i.e., change of magnification across the field of view) then if the original no. 3's are the same size the image will be the same size if the object plane is parallel to the sensor plane. Three-dimensional objects will be imaged differently across the field of view.

 

This of course has nothing to do with whether your lens is defective or not, but it does have to do with the validity of your test. If your passion is to photograph brick walls you have to be able to control this. :-)

 

Henning

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Thanks for all the explanation. I did one more unscientific test. I stood in front of a brick wall and adjust the camera framelines to be parallel to the brick lines. I agree it is not a perfect way to do the test, but the results repeated. I also did slight movements to compensate for the possible error, and the results were always the same, right corner was bad, and dept of field made actually no difference in regards to possible wrong position of the camera. Here are the shots Center, UpperRight, LowerLeft. I will do one more test by flipping the camera upside down.

 

I know noone can help me here, and the lens has to go for a replacement or repair.

I just want to see what is the other users' experience with this lens.

Did you get what this lens is advertised as?

Am I just unlucky to get two bad samples or the OA did a quick, but not thorough job?

 

I still wonder what the lens' without issues corners look like. Sorry for being stubborn here, but my expectations were higher then what the lens delivers at the moment.

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Edited by mirekti
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This of course has nothing to do with whether your lens is defective or not, but it does have to do with the validity of your test. If your passion is to photograph brick walls you have to be able to control this. :-)

Henning

 

I don't think, mirekti is in the spy business. Copying documents, etc.

But the Wate example of helged is interesting. Infinity should be sharp from left to right.

Jan

Edited by jan_kappetijn
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I made a comparison with the lower left and upper right "4". Both look like they are the same distance from the center.

http://www.l-camera-forum.com/leica-forum/attachment.php?attachmentid=424575&stc=1&d=1393446582

The upper right "4" is clearly bigger, but is it also closer? And are the difference in distance from camera big enough to make the lower left so blurry with a 21mm? (what is the distance to the wall?)

 

I was planning to buy a 21mm SEM, but this test made me reconsider it. Can someone make a similar test?

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what is the distance to the wall?

 

This one is taken today, open, and at 0.7m from the wall. https://www.dropbox.com/s/cam7vbvg0kpsx2e/L1004941.dng

The lens is stellar in the center. Actually it is so good that the corners' sharpness fall to fast so it seems it is not so sharp anymore. The latter one is not being my problem. My problem is that the corners do not behave the same, and one of them I consider to be unacceptable. I wouldn't be so sure in the results hadn't I own the same lens which had problem on the left side. To conclude, with the previos one I wasn't able to get the left side sharp, and now with this one the sharp. Had it been my mistake, I would have got one photo with the "trouble" side right, but this was not the case. I took like 20-30 photos with each one to test it.

 

In real life this won't be so noticable, and if you won't print extremly large not an issue even with my copy. However, I'd like to have what this lens is advertised, and what I paid for. I believe this is fair enough.

Edited by mirekti
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I made a comparison with the lower left and upper right "4". Both look like they are the same distance from the center.

 

The upper right "4" is clearly bigger, but is it also closer? And are the difference in distance from camera big enough to make the lower left so blurry with a 21mm? (what is the distance to the wall?)

 

I was planning to buy a 21mm SEM, but this test made me reconsider it. Can someone make a similar test?

 

I agree, I am convinced that this is the issue, wrong test setup.

 

It doesn't matter if the 3 or the 4 is a few centimeter more or less from the corner.

 

There is a huge/significant size difference indicating the sensor was not paralell to the wall at all.

 

And given focus curvature makes the image look even worse.

 

But aparently some people think they are better at testing optics than Leica.

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There is a huge/significant size difference indicating the sensor was not paralell to the wall at all.

 

And given focus curvature makes the image look even worse.

 

:confused:But aparently some people think they are better at testing optics than Leica.

 

I redid the test my meassuring the distance between each sheet of paper. Than I set the camera at what I thought it was a center, and did seven shots. Six of which

were with sligh reset of the camera position. A bit left, a bit right, a bit up and left, a bit up and right, a bit down and left, and right. In all scenarios the result was the same.

 

:confused:No, I don't thing I'm better at testing optics.

 

No need to discuss this anymore. I wondered if people could share their experience, that's all.

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Hi Mirekti

 

You have my support! It is of course a fact that Leica is best at testing Leica stuff! But so what... this does not change the fact that bad samples still exist out there! I had one... Even if I am one of those with this more or less "unlimited trust" in Leica quality, I have experienced a bad copy of a lens... An uncomfortable experience... especially after Leica tested it and found nothing wrong... but in my eyes the lens was still faulty. I was obviously hard pushed to doubt myself, but in my world that is no way to go...

 

Best regards from a happy owner of 8 other just marvelous Leica lenses!

 

Stein

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How much time wasted just because Leica does not allow the EVF magnified area to be moved into corners.

But... wait a moment... They did that on purpose to prevent us from spotting misaligned lenses ! :D

 

Anyways, can we see real shots at infinite ? Brick walls are so boring.

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Lots of drinks last night. Felt like a brick hit me this morning. :confused:

 

I think OP is making a lot of approximations here and without precise and accurate distance measurements. The 21 is a wide angle lens and if the horizontal or vertical plane is a touch off, and if the wall is not completely parallel, the corner blurring will be anybody's guess.

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