Summarit 75 vs 90 on M9

[mkur]

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Hello,

 

I plan to add a longer lens to my collection - a 75mm or 90mm. Currently, my longest lens is a 50mm. I am considering the Summarits - due to their nice rendering, low weight and attractive price (well, at least in the Leica bubble  ). I would prefer 90mm for the longer reach, however I am a little worried about my focusing ability on a M9. Some experiments with a CV 90 Apo-Lanthar showed me that at least that lens is quite difficult to focus consistently on a body without LiveView. So, is there a significant difference in focusing ease between the 75mm and 90mm Summarits? Some other lenses to consider?

 

--mk

[TomB_tx]

I've used both a Summarit 90 2.5 and a CV 75 2.5 on my M9. Never had a focus issue with the CV 75. By the time I got the 90 I found my RF needed adjustment, so I can't blame my problems on the 90 FL. Once I got my M9 adjusted I've had a good hit rate with the 90, but since I got an M10 the hit rate is better, I think due to the better VF in the M10. (Not a dramatic difference, but I find it easier.)

I'd suggest to go for the 90. For 5 decades my M lens kit was 35, 50, & 90, and I was happy with it. Since retiring I have more time to get curious about others.

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[darylgo]

When you purchase the 75mm or 90mm lens you could avoid camera focus issues by checking that your lens and camera are working well together, foregoing  adjustment.  Technically, the 75mm Summarit is a better optic than the 90mm Summarit, and rather contrasty compared to the 75mm or 90mm Summicron.  They're so close in focal length it should be a moot point however the 75mm feels more like a long 50 and the 90 feels like a short 105.    

[mkur]

Thanks for replies. I have spent some time photographing a ruler from a tripod using various lenses - I looks like that my camera has a slight front focus. That would explain the problem I had with the CV 90mm. 

[chris_livsey]

Thanks for replies. I have spent some time photographing a ruler from a tripod using various lenses - I looks like that my camera has a slight front focus. That would explain the problem I had with the CV 90mm. 

Are you allowing for the uneven distribution of the DOF in front and behind the plane of focus? Many sites that discuss using rulers etc neglect this effect which can lead to erroneous conclusions.

As a general rule DOF extends 2/3 behind and 1/3 in front of the Plane of Sharp Focus.

The fraction does change with focal length although the actual total DOF is virtually constant if the object occupies the same fraction of the image with different focal lengths.

 

If you are purely looking at the plane of focus to determine front or rear focus you may find using the moire effect more accurate than estimating by eye against a ruler, I assume this is a digital Leica as we are in this forum.

 

Although this refers to SLR micro adjustment it does have good instructions and a downloadable pattern you can use on your screen, with examples of focus shift you may see and is accurate whatever the focus system is as it looks at the plane of focus and is independent of manual or auto focus, the pattern doesn't care how you focus it just shows if the point you focus the lens at is accurate.

 

http://www.northlight-images.co.uk/camera-af-microadjustment/#af_microadjustment

Edited March 2, 2018 by chris_livsey

[Jean-Michel]

Another source for making a focus adjustment target is: http://www.squit.co.uk/photo/focuschart.html

 

It does take some care in assembling the target, but once you have but it, it is fairly easy to use. You do have to be careful in getting the camera parallel to the target.

 

I was going to buy Michael Tape's LensAlign to check the focus of my dSLRs but I found this chart to be just fine for my purposes. 

[mkur]

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Thank you Chris. This was very helpful. I did not consider the uneven distribution of the DOF - it is very likely that I have incorrectly interpreted my findings.

 

Jean-Michel - thank you for the link. That target is much better for checking focus issues than any ruler....

[Irakly Shanidze]

I have Summarit 75 and Summicron 90 Pre-ASPH. Both focus perfectly on M9. I do use a 1.4x magnifier sometimes, but just for convenience. It is not really necessary, as the rangefinder window is always the same size.

[mkur]

Based on your positive comments but not without some hesitation I decided to buy a Summarit 90mm. Surprise, surprise - it focuses perfectly on my M-E, even wide open. The lens has a modern, but not overly clinical, rendering with a nice 3d pop when used wide open. Very happy about my purchase Lesson learned - buy Leica if you want to avoid focus problems.