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Focusing 90mm AA at f2 and 3 meters impossible with Rangefinder -at least for me


dem331
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Disappointed by the results of a recent photo expedition, I carried out a test, and have reached the conclusion that I can not focus the 90 AA accurately at a distance of 2 to 3 meters.

Yesterday I tested extensively with an M240 on an empty bottle of Lagavulin and I realised that I could not distinguish the smaller writing "Single Islay Malt Whiskhy" clearly enough to determine the right focus. There is a kind of minimal turn of the lens, left or right, that does not affect the perceived focus. I could focus on the 16 years, in bigger bold letters, but not on the smaller ones. Using the EVF and x10 magnification I could hit perfect focus on the smaller letters.

My conclusion, I need to stop using the 90mm AA at apertures wider than f4 at distances below 5 meters unless I use the EVF.

I had always resisted this conclusion because I thought that other people's difficulties were due to poor focusing technique, and that some of my focusing errors were due to subject or camera movement. But no, I actually think it is actually not possible to hit the actual point of focus accurately with the rangefinder unless you have hawkish eyesight.

(the bottle of whisky had not been emptied just before conducting the test)

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Welcome to the 90mm/f2 club. It is not easy, but there are a number of techniques that help, like rocking forward and back slightly as you take a series of shots. I guess one of great things about the M240 is the alternative EVF with the zoomed in view.

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Welcome to the 90mm/f2 club. It is not easy, but there are a number of techniques that help, like rocking forward and back slightly as you take a series of shots. I guess one of great things about the M240 is the alternative EVF with the zoomed in view.

 

Thanks 

:)  

 

Treid rocking fortha nd back, but I think the problem is that my eyesight is not good enough to discern the focus, not that I can't hit it!

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The rangefinder can be difficult/impossible to use when deph of field is short. I have changed to Leica SL with its more precise focusing for such lenses; i.e. Noctilux, Summilux 75, Summicron 90 and APO-Telyt-M 135.

I think the future lies there for precision focusing. But the rangefinder is missed. Can a workable hybrid be made?  Perhaps shown at Photokina 2016?

Eric

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Maybe your focusing would have been more accurate if the bottle had still been full

The Summicron 90 AA is perfectly focusable but a demanding lens. First thing to do is to determine whether you need a dioptre, which will help with all your lenses. Visit your optometrician and  use his try-out lenses to find the correct value. Should you still have problems, use a magnifier, again with the correct dioptre, which may be different. Finally, read the focusing post in the M FAQ at the top of this forum.

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The 90AA is a tough lens to nail focus, wide open

 

However, with the SL's amazing EVF and brilliant magnification tool, this problem is a thing of the past

 

While I am a die hard M guy, I have to admit the SL does make a big positive difference to some aspects of photography where the M shows weakness

 

 

Sent from my iPhone using Tapatalk

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Are you sure the lens is well calibrated? Did you try a diopter correction lens? Did marvels for me. With 90mm lenses, DoF is very short at f/2 so focussing needs some concentration anyway. Here handheld at 1 metre. Would be better with a tripod i guess but that's the kind of result i'm used to pretty regularly.Not sure i could do it with my spectacles instead of the diopter correction lens though. No Lagavulin handy sorry

.

 

 

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Thanks for the replies, I will try the dioptre lens if I can get hold of one, the 1.25X magnifier I have, If not I will get a professional to look at it, or just stick to EVF for critical focus.  

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1.25x magnifier cannot replace a good diopter correction lens if your sight needs one. Otherwise it is easy to check if your lens and/or the RF are the culprits. Just put your camera with both the lens and the EVF on a tripod. Focus with the RF in the first place then check if the image is sharp in the EVF when using focus magnification.

Edited by lct
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Lct, I think I could probably focus the botlle of Aberlour -also a fine Whisky - 1 meter away.  The problem is when you increase the distance to 2 or 3 meters, that one (or at least I) can not see the smaller letters well enough to hit the focus point.  I will try again tonight and see what the results are.  It is also very dependent, for me at least, on the brightness of the surroundings. 

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I don't think you really need to see the letters;  a line on the label or the edge will suffice. This is from the FAQ:

 

 

Question: I come from an autofocus camera background. What is the best way to get good focus on the M9?

    The M9 works the same way as any rangefinder camera, the central patch in the viewfinder is your focusing tool.
    It is important to look through the viewfinder in the optical axis. Looking into the camera skewed will result in inaccurate focus.

    The first thing to do is to ascertain that you can see the rangefinder patch properly. A correct match between the rangefinder and your eye is even more important than it is using an SLR.
    Leica sells corrective diopter lenses. Determining which one you need - if any- can be done by going to your optician and holding his try-out lenses between your eye and the viewfinder. The one that allows you to see the rangefinder patch and framelines sharply is the correct one. Order the nearest value from Leica. In a pinch you can use over-the-counter reading glasses for this test. If your eyes need special corrections, you can use your spectacles, provided you can see clearly at 2 metres distance ( the virtual distance of the rangefinder patch). Note that the background will be at background distance,so your eye should ideally be able to accomodate over the distance differential. However, there is some tolerance here.

    For special cases there are viewfinder magnifiers. They can help, especially with longer and fast lenses and they can give confidence, but they can also be not very useful; they cannot correct errors in the focusing mechanism or your eye, in fact they magnify them.
    Also, one loses contrast and brightness.
    Leica offers a 1.25x one and a 1.4x. These need diopter correction like the camera, but often of a different value than the camera viewfinder.

    There are also third-party magnifiers, sold by Japan Exposures, that include a variable diopter correction. 1.15x and 1.35x. For patent reasons they cannot be sold in the USA and Germany for use on a Leica camera, but they can be purchased for use on for instance a rifle scope.
    Basically, for an experienced user, magnifiers are not needed and will only lower contrast and brightness, but many users do like and use them.

    Once the viewfinder is corrected optimally, there are three methods of focusing, in ascending order of difficulty aka training.

    1. The broken line method. Look for a vertical line in the image and bring it together in the rangefinder patch to be continuous.

    2. The coincidence method. Look for a pattern in the image and bring it together to coincide. This may lead to errors with repeating patterns.

    3. The contrast method. Once you have focus by method 1. or 2. a small adjustment will cause the rangefinder patch to "jump" into optimum contrast. At that point you have the most precise focussing adjustment.

    Side remarks:

    If you try focusing on a subject emitting polarized light like a reflection it may happen that the polarizing effect of the prism system in the rangefinder will blot out the contrast in the rangefinder patch, making focusing difficult. In that case rotate the camera 90 degrees to focus.
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My old sloppy "test" - AA90 @ F/4, distance about 2 meters, handheld. I held my breath as the shooting range

Edited by otho
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and F/2 from 1 meter (narrow DoF, insanely sharp lens - even dust particles are remarked)

 

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Tried this evening with an empty bottle of Cardhu at 1, 2 and 3 meters and nailed the focus at f2.  Only difference was the lighting which was brighter and a little bit more confidence in my technique. Maybe also I was not as tired as yesterday, which affects my vision.  I can not see that I could use this effectively on a non-static subject (ie. not a living object). Thanks for the examples!

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Interesting that this topic should come up as, very recently – and I assume by 90AA the 90 Summicron APO is meant – I was beginning to think that for closeups one may as well stop down to f4. In which case replace this heavy lens for hand-holding/focusing with the 90 Macro, which allows you to get even closer! Yet the 90 APO is a lovely lens and the detail can be awesome. [Attached apple mint plant, crop.]

Edited by microview
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True friend, when someone tells me he wants telemetric ask him what his visual acuity, one thing to have the corrected view because you wear glasses or contact lenses and other visual acuity is the total you have.

This is important.

 

It's easy to focus at 1 meter with f2, or f0,95, I do it every day and do well in motion.

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