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Thread: A900 manual focus pocus?

  1. #1
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    A900 manual focus pocus?

    Just tried my old 28mm Leica R lens with adapter on A900 and noticed the green focus confirmation light came on and stayed on for about 20-30 degrees rotation of the lens focusing ring. That seemed to me to be quite a lot?

    I am no rocket scientist but inspired by NASA's space program I just did a kitchen test on a row of spice flasks with manual focus at the start, middle and end of the zone where the green focus confirmation light was on and noticed slight but not enormous differences in where the focus point ended up.

    The camera has a standard G focusing screen that does enable me to eyeball what dissolves in and out of focus as I move the focusing ring. But I never find this easy to judge with a wide angle lens on any camera. So mostly I rely (maybe too much) on the green MF confirmation light.

    Sometimes I end up spinning the focusing ring wildly as I try to figure out which way I need to spin it to hit the green zone. Maybe this means I need to drink less coffee?

    So would like to ask:

    Is this amount of focus "play" in the zone where the green focus confirmation light is on normal? Is it the same when you manual focus with OEM-Sony lenses?

    Any suggestion for a technique that can be used to get manual focus spot on within the green confirmation zone? Maybe I ought to turn the focussing ring to the end of the zone then back off a little towards the middle?

    Also would like very much to hear from anybody who has found a good split screen focusing screen for the A900? I hope this would make it easier for me to be sure the focus is exactly where it is supposed to be, as I am used to doing it with my old Leica RE body that is now gathering dust in my drying cabinet while I try to figure out how to get the most out of the A900.

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    Re: A900 manual focus pocus?

    Here's a related question:

    How does the AF sensor operate? With manual focus confirmation, does the AF sensor read what is in acceptable focus depending on f stop, or is there only one very narrow area of critical focus that makes the green spot light up?

    Assuming the latter, I wonder how narrow that is? Given the DOF inherent in a WA lens like a 28mm, it seems it could vary since the DOF is greater and presumably the even the area of focus the AF sensor is able to distinguish as "critical" may be deeper than when using a longer lens. Yes? No?

    BTW, my preferred way of manual focus is to return the focusing ring to infinity after each series of shots so you always are moving the focus one way until it becomes automatic muscle memory, and hunting is all but eliminated. Also, if you look at the distance markings on the lens barrel, the distance you have to move the focus ring from infinity to normal shooting distance is quite compact ... where from closer distance markings it is a much longer throw, and therefore slower.

    - Marc

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    Re: A900 manual focus pocus?

    I had the same issue with my R50 and Leitax adapter.

    I took your advice and began focusing it exactly the way you described in the second post. It helped ALOT, but it is still maddening and tough on my eyes. I now mainly use the Minolta 50/1.4 AF lens on the a900 because frankly, I had too many misses. The hits were amazing, but they were too far and between.

    By the way, there are some guys on the Fred Miranda forum (sub forum Leica R lenses) that do stellar work with their adapted R lenses. I will send you the link in your email.

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    Re: A900 manual focus pocus?

    Quote Originally Posted by fotografz View Post
    Here's a related question:
    BTW, my preferred way of manual focus is to return the focusing ring to infinity after each series of shots so you always are moving the focus one way until it becomes automatic muscle memory, and hunting is all but eliminated.
    - Marc
    Thanks for this useful tip!

    By the way, there are some guys on the Fred Miranda forum (sub forum Leica R lenses) that do stellar work with their adapted R lenses. I will send you the link in your email.

    Also for this one! So far I am very happy with the test results from the Leica lens - apart from the focussing challenges that has more to do with my gray hair than red (leica) spots

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    Re: A900 manual focus pocus?

    So now I also find out split image focusing screens for the A900 seem to be as rare as hen's teeth. Why is that? Lots to learn!
    Last edited by lowep; 4th June 2013 at 09:13.

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    Re: A900 manual focus pocus?

    Keep going. You will either pull your hair out over this stuff (adapting R lenses to an a900) or you will just get AF lenses.

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    Re: A900 manual focus pocus?

    either pull your hair out over this stuff (adapting R lenses to an a900) or you will just get AF lenses

    exactly...maybe both

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    Re: A900 manual focus pocus?

    Or reconsider the Sony M focusing screen...

    I have tried using a Canon Ee-A precision matte-type focusing screen in a Canon 5D. Both the M and the Ee-A seem to be designed to help manual focus by making areas that are slightly out of focus appear more out of focus, making it easier to tell when focus is right-on, right? Maybe the M screen is quite similar though made by a a different manufacturer for a different camera?

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    Re: A900 manual focus pocus?

    I haven't fiddled with another screen because I am really afraid of messing up the camera. As my eyes age, I realize that AF lenses, as much as I may despise them, are more appropriate. If you want to be the "king's tester" can you let us know which focusing screens work the best?

    I have only 2 R lenses so I am not too heavily invested in them.

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    Re: A900 manual focus pocus?

    Quote Originally Posted by MikalWGrass View Post
    If you want to be the "king's tester" can you let us know which focusing screens work the best?
    Not so much new under the sun. According to this old getdpi thread and other forum posts elsewhere others have tried to do this with a mixed bag of results - none of them a complete success.

    As far as I can figure out already tested options include ordering an expensive non-OEM custom-made screen (discussed in this thread on a German forum that I google translated) or a cheaper one like the Bresson advertised on ebay however if this thread on a Nikon website is anything to go by that may also have its drawbacks. Or the Sony M screen reviewed here that is designed to enhance manual focus but is not split prism.

    Before trying to make one for myself out of a cornflakes packet and an old pair of reading glasses I will try to find a Sony M screen and also look for a good preloved 35mm AF lens for jobs where reliability and ease of use is imperative.

    Quote Originally Posted by MikalWGrass View Post
    I have only 2 R lenses so I am not too heavily invested in them.
    I also have 2 R lenses so I am heavily invested in them

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