Minolta AF 35-200 overexposure

[minrato99]

Hi,

I have a Sony Alpha 200, and I am taking very appropriate photos with it, using the 18-70 kit lens.

However, when I use my Minolta Maxxum 35-200 AF lens with my Sony Alpha 200, set in AUTO, I see that the pictures are overexposed.

Any explanation or clue?

As you see, I am an amateur, far from being an expert.

Thanks,

Paulo

[KevinBarrett]

If it is just that lens, the solution is simple: simply use the exposure compensation dial on the front of your camera's grip. Move it to the left until the exposure is what you were expecting, and remember that spot for the future! I don't know what the UI for the a200 will do, but my a700 will remember this setting in each of the PASM modes, but if you move between full auto and the scene modes, you'll have to dial it back every time.

Also, welcome to the forum! I'd encourage you to share your photos with us, but it sounds like you aren't particularly happy with what you're getting...heck, share them anyway and we'll help however we can!

[Greg Beetham]

The 35-200 isn't one I've ever used but there is the sticky apature problem that can crop up in older lenses from time to time, usually the only way to fix it is to get the apature iris cleaned (disassemble the lens and remove any oil that has gotten onto the blades), apart from that I don't know what it could be.
Greg

[minrato99]

Thanks a lot for your replies.

The manual compensation dialing to the left works somehow, but...

Shouldn't the camera recognize the light and compensate automatically in the AUTO mode?

Paulo

[Dusty]

Paulo,

If both the lens and camera are working properly, it should. Remember, the camera is metering at wide open and stopping down to shoot. Dirt on the aperture blades or linkage, a bent, binding or sticking lever, anything that slows of freezes the aperture closing could be the culprit.

You can try to take some photos at wide open and see how they come out.If they expose properly, it's because you're no stopping down properly. If they are overexposed, you may have an aperture that's stuck partly closed. If the lens tells the camera it's an f3.5 lens, but the aperture won't fully open for metering, the camera logic is going to assume that you're in a lower light situation, and it will over expose.

Dusty

[Greg Beetham]

I hardly ever, well never really when I think about it, use AUTO mode, but I think it's biased towards 400ISO, if so there is a chance that the predetermined f/stop that was computed for the lens...say f7.1 or whatever, didn't actually occur during the exposure due too mechanical problems (sticky diaphragm) the lens may have only closed down to f5.6...for example, thus resulting in an overexposure. This is only supposition though, try the same settings in A mode too check, look at the Histo and get the exposure parameters for a dud AUTO exposure and see what you end up with. You will need too know what ISO it chose and what f/stop, you can't set the shutter in A mode but that still should end up the same if the light value hasn't changed between shots and the composition of the shot is the same, it would probably be best to do the test on a tripod aimed at a brick wall, that way there can be little chance of some metering mode differences creeping into the situation.
Greg
ps. You can check if the diaphragm is oily...usually, with the lens off the camera get a bright torch and look into the rear of the lens, the iris should be fully closed, if it isn't there are problems, if it is you might be able too see some oil on the blades...or not, you can also move the iris quadrant with your fingernail and let it snap back, it should snap back instantly.

[minrato99]

Hi,

I'm back to say that when I use this M AF 35-200 lens mounted in my ancient Minolta Maxxum 700si, in the AUTO mode, the pictures are just perfect, with no problems with overexposure at all.

I suppose this is an evidence that rules out a possible problem with the lens itself, but maybe I'm wrong...

Still accepting opinions about the fact.

Thanks,

Paulo

[Dusty]

Paulo, you can't do a direct comparison between the 2. One may have a stronger actuator for the aperture lever.

Dusty

[01af]

... or one set of frames were taken in bright light, with the lens stopped down, and the other set of frames was shot in lower light, with the lens wide open.

If the aperture blades are sloppy due to being contaminated with oil then this will produce over-exposed frames only when trying to stop the aperture down. When using the lens wide open, everything will be fine.

Paulo, why don't you simply take a look at the aperture blades?

-- Olaf

[minrato99]

Hi, Olaf,

I tried to take a look inside the lens through both ends to see the aperture blades, even using a bright light (as recommended by Greg Beetham), but I could't see anything, and I'm afraid of disassembling it.

Thanks,

Paulo

[pakodominguez]

Well, you can put the camera on A mode and take a series of pictures at f 4.5; f5.6; f8; f11 and f16. If the pic at f4.5 looks good and the one at f11 looks overexposed, the blades are not working properly.

Regards

[minrato99]

Well, you can put the camera on A mode and take a series of pictures at f 4.5; f5.6; f8; f11 and f16. If the pic at f4.5 looks good and the one at f11 looks overexposed, the blades are not working properly.

Regards

Hello,

Done! The test you suggested showed that going from 4.5 to f11 the image gets overexposed.

Using the same test with the kit lens 18-70 the pictures are just OK, looking correctly exposed to me.

May I safely run the risk opening (disassembling) the lens to try to fix the possible defect by myself?

Thank you.

Paulo

[01af]

I tried to take a look inside the lens through both ends to see the aperture blades, [...] but I couldn't see anything ...

If you cannot see any aperture blades at all then they are seriously stuck in wide-open state. No wonder you're getting over-exposed shots (except when shooting at full aperture anyway).

-- Olaf

[Javelin]

yesif you can see right through then the aperture is all the way opened. I wonder though if it might have opened too far and got stuck never seen it before but maybe of somone was playing with it.

[pakodominguez]

Hello,

Done! The test you suggested showed that going from 4.5 to f11 the image gets overexposed.

Using the same test with the kit lens 18-70 the pictures are just OK, looking correctly exposed to me.

May I safely run the risk opening (disassembling) the lens to try to fix the possible defect by myself?

Thank you.

Paulo

Paulo,
I imagine the Xi lens quite complex lens: I would prefer to take my equipment to a qualified technitian.
Regards