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Need help, A99 over-exposures vs viewfinder image

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paso144 View Drop Down
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Post Options Post Options   Quote paso144 Quote  Post ReplyReply Direct Link To This Post Topic: Need help, A99 over-exposures vs viewfinder image
    Posted: 16 May 2022 at 17:12
Fellow Dyxumers,

I need some help to find the correct settings for my A99 body. As you might know I'm shooting a lot of panning shots. Sometimes there is a lot of light and I need to stop down to enable the correct long exposure times of 1/30sec in combination with low ISO values of 100 or 50.

Yesterday I was at the bike park in Winterberg with a lot of sun and I noticed again that my pictures are completely washed out while my viewfinder indicates correct exposure. I had to compensate with 5 stops of exposure to get the resulting picture right but then my viewfinder turned almost black and it was like I'm hunting ghosts during panning.

I would like to understand if this is a viewfinder quirck or if there are possible settings to correct this. Hopefully other panning guys who use the A99 body can help me out.

To show this effect I shot the below pics with my mobile from the live view. As it was an overcast day I mimiced the light conditions by setting ISO to 1600. The first pic shows the viewfinder indication and as visible it shows a perfect exposre with 1/30sec and F10. The second picture shows the result which is clearly overexposed by at least 1 stop. Although not as severe as the results with even brighter weather it shows the issue I'm trying to tackle.

1) Viewfinder image before taking the shot.


2) Playback of actual shot on viewfinder.

A99, A850, 16fish-eye, 17-35G, 28-70G, 24-105D, 28-135, 50/1.4D, 50macroRS, 58/1.2, 85/1.4D, 80-200/2.8APO black, 100macroD, 100/2, AT-X304, 500mirror, 5600D HS.
 



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Phil Wood View Drop Down
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Post Options Post Options   Quote Phil Wood Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2022 at 17:50
This is a common effect from a lens with a sticky iris - and a number of the lenses in your signature are vulnerable to the problem. What lens are you using? Have you tried a different lens?

The A99 adjusts the electronic viewfinder image to compensate for the closure of the aperture, if the aperture doesn't close fully over-exposure is the result.

You can check the aperture manually, just open it by moving the aperture lever on the lens, when you release it it should snap closed very quickly. You can also do a visual check - close the iris and see if it is an even grey colour, if there are dark smears along the edges of the blades you are almost certainly looking at oil, the cause of the sticking..
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paso144 View Drop Down
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Post Options Post Options   Quote paso144 Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2022 at 18:02
Phil, unfortunattely your spot on. Just checked my aperture and it is slow. Not an issue on a 50mm as I cleaned lots of them but my 80-200 is quite complex on that. Will give it a shot though.
A99, A850, 16fish-eye, 17-35G, 28-70G, 24-105D, 28-135, 50/1.4D, 50macroRS, 58/1.2, 85/1.4D, 80-200/2.8APO black, 100macroD, 100/2, AT-X304, 500mirror, 5600D HS.
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2manycamera View Drop Down
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Post Options Post Options   Quote 2manycamera Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2022 at 18:12
I hope Phil is correct, but there is a second possible issue in the a99 body. I purchased a used a99 a few years ago from a reliable dealer and had the same issue with any lens used except at the largest aperture. The store that sold it, took it back for repair but ultimately gave me a full refund because the fault was in the body and was not an "economical repair" for them. Cheaper to give me the refund. It's been long enough ago that I cannot remember the precise problem, but it had to do with the lever in the body that stops the lens down when you take the shot. Got a second a99 from another dealer and there were no issues with any lenses I own.
7D a68 a99 a6600 a7Rii 16/2.8 24/2.8 28/2 35/2 50/1.4 100/2 200/2.8 24-70CZ 1.8/135 80-200/2.8 24-105 28-135 300/4 16-50DT 70-300G Tam 90/2.8, E55-210 E2/12 Sig E1.4/16,30 & 56, FE15/4.5V
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Phil Wood View Drop Down
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Post Options Post Options   Quote Phil Wood Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2022 at 23:04
Sorry it's the 80-200, a far more complicated fix than a prime. I assume everything is working correctly with other lenses? Best to double check before taking the srewdriver to the lens.
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SnowFella View Drop Down
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Post Options Post Options   Quote SnowFella Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2022 at 08:45
Depending on what 80-200mm it is the service manual for the older black version is available to be downloaded from allphotolenses.com.

Minolta 80-200mm page.

Think the only difference to the white one is the AF gearing but don't hold me to it.
 



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paso144 View Drop Down
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Post Options Post Options   Quote paso144 Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2022 at 09:24
@SnowFella, thanks for the link but I have the original CD from Pete Ganzel, although no CD-tray anymore in my laptops . Luckily it's all on my hard-drive already.

Torn her down yesterday evening and replaced the whole back-group including diafragm with the one from my old 80-200 which was to beat-up to safe. Now I'm building her up again. Of course I damaged the brittle flex so I will need to do some soldering to replace the flex neck with wires. Already had to do the similar exercise on my 17-35G (with success).

If interested I can take some more detailed pictures of the tear down as it is not always very obvious from the repair manual how things are assembled together and what you should loosen or not.

Maybe I should start my own Tinkering page
A99, A850, 16fish-eye, 17-35G, 28-70G, 24-105D, 28-135, 50/1.4D, 50macroRS, 58/1.2, 85/1.4D, 80-200/2.8APO black, 100macroD, 100/2, AT-X304, 500mirror, 5600D HS.
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Post Options Post Options   Quote SnowFella Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2022 at 12:29
Best hold on to those original service manuals as as far as I gather Pete won't be around to sell them again sadly.
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Phil Wood View Drop Down
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Post Options Post Options   Quote Phil Wood Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2022 at 18:30
Originally posted by paso144 paso144 wrote:

@SnowFella, thanks for the link but I have the original CD from Pete Ganzel, although no CD-tray anymore in my laptops . Luckily it's all on my hard-drive already.

Torn her down yesterday evening and replaced the whole back-group including diafragm with the one from my old 80-200 which was to beat-up to safe. Now I'm building her up again. Of course I damaged the brittle flex so I will need to do some soldering to replace the flex neck with wires. Already had to do the similar exercise on my 17-35G (with success).

If interested I can take some more detailed pictures of the tear down as it is not always very obvious from the repair manual how things are assembled together and what you should loosen or not.

Maybe I should start my own Tinkering page


I did try to get the CD (I can still read them) but I was too late, Pete was no longer with us. As I recall there are manuals on the CD that are not available online (I was probably looking for a 35-200xi repair manual).

Any strip down/build up photos would be a valuable resource. As the lenses get older they are more likely to need to be home-serviced.
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paso144 View Drop Down
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Post Options Post Options   Quote paso144 Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2022 at 12:47
@Phil Wood, OK will take a shot at pictures when I re-assemble her.
A99, A850, 16fish-eye, 17-35G, 28-70G, 24-105D, 28-135, 50/1.4D, 50macroRS, 58/1.2, 85/1.4D, 80-200/2.8APO black, 100macroD, 100/2, AT-X304, 500mirror, 5600D HS.
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