Problems using aperture ring

Yep... me too. Zoom lens, what's that ?

No bad thing in my eyes!

In the week since receiving my 28mm and 50mm, no other lens has been on my camera and I've taken in the region of 300-400 shots (this may not sound a lot to some, but I work about 60 hours a week and I'm also in rehearsals for the Seagull).

I'm loving the older lenses, I find they add a lot of enjoyment to my photography.

That said, the 10-17 fisheye will remain a permanent fixture in my set-up, it's just a lot of fun to use.

Are you sure you are metering at the aperture you have set? I have two M lenses that I use with my K10d, and I have two ways of metering. The quickest is to set the aperture desired and press the green button. the camera will set the shutter speed following the program default mode. I have my program mode set to MTF, so I get the standard program settings with manual lenses that the camera does not know the MTF aperture settings for.

The second, and I prefer it when I have the time to use it, is to use the optical depth of field preview. This puts an exposure meter into the viewfinder while it is held over stopping down the lens.

The last thing that will get you is that with the standard focusing screen the exposures are off the wall. They can be over at one setting under at another and spot on at a third. With the LL-60 screen I bought on eBay, my exposures are perfect with all lenses. The screen is out of the *ist series of DSLRs. If you are going to be using manual apertures to any great extent, this is the way to go. I use my M 400/5.6 and M 100/4 macro a lot.

The *ist DS screen doesn't fit all other models, and anyway can't solve the non-linear problem that some of us get with some lenses.

Cameras up to and including the K20 can use the *ist D screens. I have no problems with non linear responses on either of my lenses. I did have a mild problem at the smallest apertures (22,32,45) on my 400, but had it cleaned, lubed and adjusted and now it exposes exactly the same whatever stop I select.

The fact is that many of us do experience a non linear problem. I don't see how a different focusing screen can fix a non linear problem. I had the problem with an *ist DS anyway (non linear), with the original screen.

I suspect that some users don't get the problem, or not so seriously, because there is something different about their particular lenses.

I thought the K100D and K200D take a different size screen, or is that not so?

No, the same screen fits all.

Why do Katz Eye supply different screens for different models?

See http://www.katzeyeoptics.com/cat--Pentax-DSLRs--cat_pentax.html

"Even though the screens look similar, many will not interchange!"

I have no idea why Katz Eye do that. The screen from the *ist D works and fits identically on my K10, even though Katz Eye say the K10 needs a different screen. The K7 is probably different because of 100% viewfinder coverage, but I don't own a K-7 so I cannot test it out.

The *ist D, *ist DS, K10D and K20D have pentaprism viewfinders, so I can believe they can take the same focusing screens.

The rest have pentamirror viewfinders, so I can believe it if they need a different size of screen.

I think it's best not to state that the *ist D screen fits ALL models up to the K20D unless that is known for certain.

I'd also like to point out to those considering a change of screen that the early ones are not as bright as later ones, so you will suffer a dimmer viewfinder in the attempt to correct the exposure problem. And it won't correct a non-linear exposure problem anyway.

I never thought of that aspect! Thank you for pointing it out. Perhaps the Pentamirror viewfinders do take a different screen. I do know from the Pentax Forum gang that the older screens make the camera work much better when lenses are set to a specific aperture on the lens.

The screen is slightly darker than the original K10 screen, and is linear in response to the light. My manual lenses meter correctly with the older, darker, screen. Response is correct at all apertures, contrary to the claim above that the response is not linear. It also has not lost its accuracy metering with my DA series lenses, which was something I was worried about.

I have read speculation that the brighter screens are the cause of the metering problem, and I can believe it. I also have more accurate depth of field preview with the older screen. The k10 default screen does not accurately portray the depth of field to me at wider apertures. It seems to hit a depth of field and then hold it all the way to the widest stop. As I use the optical preview, and have done for some 49 years now with Pentax cameras, I am more concerned with accuracy than brightness.

With the LL-60 *ist D screen, my metering and viewfinder have returned to what I expect, whatever the reason may be.

I'm not claiming everyone gets a non-linear problem. It may depend on the particular lenses.

I got a non-linear problem with my *ist DS and the original screen and Pentax-M 100mm f2.8 and Pentax-K 135mm f2.5. So I don't believe changing the screen will fix everone's problem.

Pete, I can believe that you found the problem you have. For both my M lenses (400/5.6 and 100/4 macro) all my exposure metering problems quietly went away when I installed the LL-60 screen. I have just received my M42>K adaptor and a (hard used) SMC Takumar 55/1.8. I should be able to try them out over the weekend and see if I have any problems with metering. I shouldn't because the lens will be in stop down metering only, but one never knows.

K100D K110D K200 and K-m all take an L90 screen I believe.

The metering with my M series 100mm/f2.8 on the K20D and a standard screen is dire. The only lens which seems to be further out is the Vivitar 28mm/f2.8 close focus.

K.