Tamron SP 24-135mm with the K20D - exposure problem

pentaxmz · 01-20-2009, 05:02 PM

Hey folks,

I just begun using one of my older film SLR lenses. This Tamron is actually a pretty nice lens (it is the 50th anniversary gold lens).

Anyhow, I found that I must move the exposure compensation up by 1 1/2 stops in order to get a fairly accurate exposure compensation. Why is this?

I thought that exposure compensation was independent of the lens. That is, the sensors simply read the light as it is at the penta-prism area.

Wait a sec... [thought in progress].... I think this is related to misreading the aperture of the Tamron lens.

Is there a way to automatically compensate for proper EV whenever this lens is attached?

Thanks,
Shawn

Stratman · 01-20-2009, 06:05 PM

Does the lens have the "A" setting on the aperture ring?

pentaxmz · 01-20-2009, 06:27 PM

Originally posted by Stratman

Does the lens have the "A" setting on the aperture ring?

Yes and it is almost always locked on A, at least, for the purposes of this question.

BTW, my Sigma APO 70-300mm does not exhibit this EV problem. I have not tested my other lenses yet.

Stratman · 01-20-2009, 06:49 PM

I have a Cosmicar 28mm f2.8 that is the same way, it has the "A" setting also, I have to dial in big time EV compensation to get a decent exposure with it. I have no idea why, but I guess it might just be a defect or a quirk in the lens.

01-20-2009, 05:02 PM	#1
pentaxmz Veteran Member Join Date: Dec 2008 Location: Seattle Posts: 659	Tamron SP 24-135mm with the K20D - exposure problem Hey folks, I just begun using one of my older film SLR lenses. This Tamron is actually a pretty nice lens (it is the 50th anniversary gold lens). Anyhow, I found that I must move the exposure compensation up by 1 1/2 stops in order to get a fairly accurate exposure compensation. Why is this? I thought that exposure compensation was independent of the lens. That is, the sensors simply read the light as it is at the penta-prism area. Wait a sec... [thought in progress].... I think this is related to misreading the aperture of the Tamron lens. Is there a way to automatically compensate for proper EV whenever this lens is attached? Thanks, Shawn

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Problem setting exposure with K-7	sceadgugenga	Pentax DSLR Discussion	7	10-14-2010 02:33 AM
Mode m exposure problem?	CrossStealth	Troubleshooting and Beginner Help	23	02-14-2010 05:21 AM
Tamron 28-75 f/2.8 over exposure problem	Sew-Classic	Pentax SLR Lens Discussion	13	10-22-2009 02:49 PM
For Sale - Sold: Tamron SP 70-210mm f/3.5, Tamron SP 28-135mm f/4.0-4.5 28A, Tamron pk/a adapta	hinman	Sold Items	14	05-08-2009 05:35 PM
K20D and FA50 continuous-shoot exposure problem?	defiant	Pentax DSLR Discussion	6	04-22-2009 08:57 AM

01-20-2009, 06:05 PM	#2
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	Does the lens have the "A" setting on the aperture ring?

01-20-2009, 06:27 PM	#3
pentaxmz Veteran Member Join Date: Dec 2008 Location: Seattle Posts: 659 Original Poster	Originally posted by Stratman Does the lens have the "A" setting on the aperture ring? Yes and it is almost always locked on A, at least, for the purposes of this question. BTW, my Sigma APO 70-300mm does not exhibit this EV problem. I have not tested my other lenses yet.

01-20-2009, 06:49 PM	#4
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	I have a Cosmicar 28mm f2.8 that is the same way, it has the "A" setting also, I have to dial in big time EV compensation to get a decent exposure with it. I have no idea why, but I guess it might just be a defect or a quirk in the lens.