Tamron 70-210 AF zoom overexposing by ~3-4 stops

[wisp]

Hi all,

I thought I had seen something related to this at one point, but was unable to

find it in a search. My tamron zoom is overexposing by 3-4 stops (and yes, it

is the lens - if I switch the lens, the camera meters fine) - could this be a

case of dirty contacts on the lens? If so, what is the best way to clean it? I

have some ?sp? kaig deoxit gold. It is an older lense given to me by my father.

Camera is a new D200.

 

Thanks in advance.

[soeren_engelbrecht1]

If you shoot wide open, does it still overexpose ?? My guess would be "no"... To test, run a series of exposures at F/4.0, F/5.6, F/8.0, etc. If the pictures are more and more overexposed, the aperture is not closing down correctly.

 

I do not know if the D200 would stop down a third-party lens mechanically or electronicaly, though. If it is mechanical stop-down, you might want to set the aperture ring to, say, F/16 and wiggle the aperure stop-down mechanism to see if the problem lies there...

 

Cheers,

 

Soeren

[albert_smith]

If the meter is giving a realistic exposure combo, say f/16 @ 1/125th in bright sunlight with ISO 100 speed film, but the resulting film is over-exposued, I would check the action of the aperture blades. You can do this right away without shooting film.

 

Take the lens off of the camera and set the aperture ring to the smallest f-stop (f/22 or there abouts). Now locate the small lever that actuates the aperture for the exposure on the back of the unmounted lens. Flick this lever and observe the action of the blades. They should close and open with no delay or stickyness.

 

If there is any delay, then the camera may be set to say f/11, but the actual taking aperture could be several stops wider because the shutter could actuate prior to the blades fully closing to that f/11 setting. The result could be that 3-4 stop over-exposure.

 

FWIW... I saw this same thing when I got back 8 rolls of film from my FM2 and AF 35mm f/2.0 Nikkor. Most every shot was ruined due to overexposure. When I did that lever check that I mentioned in the previous paragraph, it took almost 10 seconds for the blades to close from f/2 to f/22. Of course, the camera assumes this action is instant, and the shutter fired while the true aperture was way more open that what I had set.

[wisp]

IIRC, the lense was wide open when this was happening (light was low) - I'll check again. I tested manually locking down the aperture - the action seemed fine (and fast) - no stickiness.

 

I assume from the responses that a CPU contact is an unlikely cause. I'll experiment a bit more, but I am kinda stumped.

 

thank you for the responses so far

[wisp]

one more thing - the meter was not giving realistic exposures - marked difference in metered shutter speed vs my other lenses (same aperture)

[wisp]

retested - the lens only overexposes when in an 'auto' mode - when fully manual, the lens gives the same exposure results as other lenses (under the same lighting conditions with the same settings) - this leads me to believe that there is nothing mechanically wrong with the lense. I also cleaned the contacts with Caig DeoxIT - no change.

 

I am really stumped as to what could be going on here - when I look at the EXIF data for the images, the correct focal length and aperture are displayed (what I shot with)

 

Is it possible somehow that this lense is incompatible with matrix metering? (ok, so I tested this: the lense exposes properly with spot metering (on an approx 18% gray subject) - it is overexposing with matrix metering) - any idea whether this is a known issue with older 3rd party lenses?

 

thanks.