Originally posted by Ian It seems to me that this whole issue of metering with the older lenses could be solved very easily by a small firmware fix.
The existing focus screen works just fine for metering, provided that the camera has information about the actual aperture settings so that it can meter through a wide-open lens and make the necessary calculations about the exposure required when the lens stops down.
What is the difference between an A-series lens and an older K or M series lens? Or between an A series lens on and off the ´A´ position? As far as I can see the only difference is that in the case of the older lenses (or the A lenses in manual mode) the camera does not know what the wide-open apature is, or to what aperture the lens will go to when taking the photo. It can obviously stop down the aperture to the selected value with the green button, or the optical preview, but this is evidently not a satisfactory solution for metering with the hardware in the k10.
The fix to this problem is to give the computer in the camera the information it has when using A series and later lenses. This is 1. the wide open aperture and 2. the aperture to which the lens will go to when the shutter is open.
The wide-open apeture could be entered in the menus in the same way as the focal length is, and perhaps one of the e-dials could be used to tell the camera where the manual apeture ring was set to. This would give the camera the same information that it has available to it when using an A series lens, and would probably enable multi-segment metering with any of the old lenses as well.
Pentax need to be persuaded to implement this in a firmware upgrade. It would be very easy for them to do - no new actual features, just an extra entry in one of the menus. Probably the place to put it would be in with the ´use aperture ring´ selection.
Ian
After a few people suggested a firmware fix I thought that a bit of contemplating on a workflow scenario. First you could pre-program all your manual lenses and include the wide open f stop (BTW this would instantly fail for lenses w/ smaller tha f4 aperatures ie mirror lenses and some on 2x teleconverters) (ANOTHER note: even "A" lenses w/ "A" teleconverters should fail if the effective f stop goes above f8, which may happen in larger,slow zooms. Something to check on). Now you could choose your lens in a menu.
Then meter w/ the green button at wide open (see notes above).
Then tell the camera what f stop you want to use (camera will decide on speed based on the above)and
then take the picture if you have a speed/aperature combination to your liking.
Unfortunately this only works for aperature priority (which is what you set it for basically)
Seems to me dropping a DS screen in is much quicker, permanet, global and doen't screw anything else up too badly.
And shoot, check histogram, reshoot is at least as fast. And you can choose either to change shutter speeds or aperature........ No the software fix is too cumbersome for me.
If this was an easily solveable issue by Pentax, it would be solved. My guess is this is just a minor way of pushing new glass, short of the Canon way of just ditching the mount all together.
Since the old screens weren't "broken" and there is not a ton of praise for the new screens (adds really nothing AFAICT), it just seems like an out and out mistake in engineering logic.........probably made a lot of sense in marketing, bean counting logic though. Pentax HAD to know the implications of the new screen on manual focus lenses or they are all brain dead there in R/D.........