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a850 and fully manual lenses overexposes...?

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addy landzaat View Drop Down
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Posts: 13084 		Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2016 at 18:29
Originally posted by MichelvA MichelvA wrote:

Not sure if my comment helps, but i use the A900 (which is more or less the same as A850) and it sometimes tends to overexpose with some AF lenses too - especially when there is much sunlight. I usually shoot in RAW so can adjust later, but it is annoying indeed.
I have my A900 set to .7 over exposure as it tends to underexpose

I never noticed any problems as described with my Vivitar 13/2.8 (a.k.a. Samyang 14/2.8).
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bull drinkwater View Drop Down
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Posts: 93 		Post Options Post Options   Quote bull drinkwater Quote  Post ReplyReply Direct Link To This Post Posted: 12 September 2016 at 06:23
I have a number of fd lenses and have no problem, with the lens wide open I focus, then I set the apaturel. witjh the camera set to manual I center the ev scale and most times i'm right on.with the shutter speed.
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bull drinkwater View Drop Down
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Posts: 93 		Post Options Post Options   Quote bull drinkwater Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2016 at 12:09
Originally posted by sploosher sploosher wrote:

I find it hard to understand how using a fully manual lens on a DSLR functions properly.....

As there is no electrical connection between the two, how does the camera know what shutter speed to use for a preset aperture.

this is the issue that is stopping me from getting more fully manual lens`

I have a 200mm f2.8 canon fd lens that I use on all my a-mout cameras. this is how it workc for my.
1 I set the camera to manual.
2 I pick a iso.
3 I focus wide open, then set my apaturwe.
4 I center the ev pointer, that sets the proper shutter speed.
it also works with a 500mm f8 mirror lens.
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luke View Drop Down
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Posts: 894 		Post Options Post Options   Quote luke Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2016 at 13:25
Originally posted by sploosher sploosher wrote:

I find it hard to understand how using a fully manual lens on a DSLR functions properly.....

As there is no electrical connection between the two, how does the camera know what shutter speed to use for a preset aperture.
...


The same way as an ordinary SLR: it has some metering sensors with the mirror box which (more or less) constantly measures the light levels. Or perhaps I don't understand the question...
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Chaiwallah View Drop Down
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Posts: 1 		Post Options Post Options   Quote Chaiwallah Quote  Post ReplyReply Direct Link To This Post Posted: 23 June 2022 at 14:05
I recognize that this is an old thread, and the a850 was discontinued a dozen years ago, but I'm just having this poster's experience now and think I can shed some light on it. I had an a850 for ten years or so until it was stolen six months ago. I just replaced it. I like to shoot with vintage lenses and have a good collection of them. I never had the overexposure problem with the first a850 but am having it now (which is what brought me to this discussion). I'm glad to see that I'm not alone in experiencing this. Otherwise I would think my camera is defective. There is a difference between my current a850 that's overexposing and the older one that didn't and that's the focusing screen. In the older camera I replaced early on the general screen (G?) with a screen that was better for manual focusing (M?). They are hard to find now and $300 plus shipping for a used one is an unacceptable price for me. It looks like setting exposure compensation to -.7 stops may be necessary with the manual lenses. I also shoot RAW, so it's a minor inconvenience. I hope this helps someone.
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XKAES View Drop Down
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Posts: 160 		Post Options Post Options   Quote XKAES Quote  Post ReplyReply Direct Link To This Post Posted: 23 June 2022 at 15:12
Thanks for mentioning this. I have no idea how many a850/a900 users switch out the original G screen for an M or L screen, but if they do, they need to go into the SETUP menu and tell the camera what screen it has -- because it adjusts the metering somehow. The instruction sheet that comes with the new screen explains how to do this. If not done, it can lead to exposure errors.

On the other hand, I've seen instances where the SETUP menu has been changed but the focusing screen has not been changed. This will also cause exposure errors.
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addy landzaat View Drop Down
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Posts: 13084 		Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2022 at 08:17
Originally posted by Chaiwallah Chaiwallah wrote:

I recognize that this is an old thread, and the a850 was discontinued a dozen years ago, but I'm just having this poster's experience now and think I can shed some light on it. I had an a850 for ten years or so until it was stolen six months ago. I just replaced it. I like to shoot with vintage lenses and have a good collection of them. I never had the overexposure problem with the first a850 but am having it now (which is what brought me to this discussion). I'm glad to see that I'm not alone in experiencing this. Otherwise I would think my camera is defective. There is a difference between my current a850 that's overexposing and the older one that didn't and that's the focusing screen. In the older camera I replaced early on the general screen (G?) with a screen that was better for manual focusing (M?). They are hard to find now and $300 plus shipping for a used one is an unacceptable price for me. It looks like setting exposure compensation to -.7 stops may be necessary with the manual lenses. I also shoot RAW, so it's a minor inconvenience. I hope this helps someone.
Great information, thank you for sharing.

And welcome to Dyxum, Chaiwallah
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Phil Wood View Drop Down
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Posts: 2400 		Post Options Post Options   Quote Phil Wood Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2022 at 11:04
I too am new to this thread, but I find comments here interesting.

Originally posted by sploosher sploosher wrote:

I find it hard to understand how using a fully manual lens on a DSLR functions properly.....

As there is no electrical connection between the two, how does the camera know what shutter speed to use for a preset aperture.

this is the issue that is stopping me from getting more fully manual lens`


The lack of communication is resolved by the camera assuming that the aperture is a constant, that the lens is not wide open and expecting to close during the exposing process. So all it has to do is measure the light level it is seeing and adjust shutter speed and/or ISO to ensure correct exposure. Thus you can use the camera in M or A modes and get nicely exposed images.

Many manual lenses have automatic aperture linkages to close the iris down during the shot, the A850 etc will not do this and many lenses have no way to manually close the iris, so you need the adapter to include a control to do this or some other bodge to allow you to use the lens shut down (eg the flange on some M42 adapters).

This does mean that the viewfinder image darkens as you manually adjust the aperture for DOF etc. For this reason an EVF can work better, you can actually see the effect of your settings on the exposure level in the viewfinder (not to mention the assistance provided by focus peaking).

Originally posted by bull drinkwater bull drinkwater wrote:

I have a 200mm f2.8 canon fd lens that I use on all my a-mout cameras.


I have an historic affinity to FD lenses, but didn't realise that could be used on A-mount. What converter is there for FD to MA? Does it include glass?
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Phil Wood View Drop Down
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Posts: 2400 		Post Options Post Options   Quote Phil Wood Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2022 at 11:15
Update - I have found FD to AF adapters on ebay - one from Fotodiox with glass, others without glass and hence without infinity focus.

I think I shall resist that particular nostalgia trip until I get a full frame E-mount body.
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