April 2, 2010
How do you set the aperture on a pentax 35mm film camera when using a Tamron lens?
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It’s a Pentax ZX-M and the lens is a Tamron 28-80mm f/3.5-5.6. I don’t know how to set the aperture. I’m trying to do shallow DOF and great DOF, but when I set the aperture and move the zoom, the aperture changes.
what else do you guys need to know?
Filed under Pentax 35mm Cameras FAQ by on Apr 2nd, 2010. Comment. 
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Comments on How do you set the aperture on a pentax 35mm film camera when using a Tamron lens?
Would need to know the kind of lens and which model Pentax.
on nikon and cannon i know there is a mode called aperture priority it is the one with the a sorry i have never shot pentax good luck
If it is a newer Tamron lens designed for newer electronically controlled cameras, then you can’t set it. More than likely, the Pentax camera will require an older lens with a manually adjustable aperture ring on the lens itself.
As the other answer said, you not giving any SPECIFICS on the lens and camera make it almost impossible to answer your question factually.
steve
EDIT: Ok, I see you have added more details, thank you for that. Your question then is actually how do you MAINTAIN the aperture you have set. The answer is you can’t. Look at the specs on your lens. When an aperture is stated as 3.5 – 5.6, that means it is not a constant aperture lens. Those specs mean the minimum aperture will change to those values as you zoom the lens. At it’s widest angle, the aperture can be set to 3.5, but if you zoom it out, it WILL by design change to 5.6. You can, however, set an aperture of any number higher than 5.6, and it will maintain it throughout the zoom range.
A zoom lens that does NOT change aperture is known as a CONSTANT APERTURE lens. It would state an aperture spec of for instance 2.8, and if you set it there, it will maintain it throughout the range. These lenses are MUCH larger, MUCH heavier, and MUCH more expensive.
There is nothing wrong with your camera, lens, or you, it is simply the normal design of the lens.
How do you ask a question without providing any information about your equipment?
Do you have any idea how many models of Pentax 35mm cameras there are and how many Tamron Lenses exist for those hundreds of 35mm cameras?
Give some information that’s useful.
In answer to your question,… I don’t, you won’t and neither will anyone else be able too because your question borders on totally silly.
..
Make sure the camera is on aperture priority.
It sounds like you’re on shutter priority. When you try to take a picture the camera checks the speed that’s set and adjusts the aperture to get the best picture, overiding your aperture setting.