Originally posted by Fogel70 As I said, I don't think it will help much by inputting max aperture of the lens as long as the camera don't know which aperture is used when stopping down.
I think you missed the point a little, based upon the long running discussions regarding stop down metering and manual lenses.
there are 2 things manual lens users would like, one of which is possible, and relatively simple, the other which while possible, is probably never going to happen because it will be somewhat less reliable.
I will deal with the second point first.
Ideally, a manual lens user would input maximum and minimum aperture, set the lens to minimul aperture and let the camera control the lens through the aperture activation lever. While this can work, the biggest problem is that the pentax K mount lenses controlled the aperture diameter linearly, where as KA lenses control the aperture area linearly with movement of the activation lever. As a result, if you consider stopping down to smaller apertures, exposure control would be extremely difficult because of the non linearity of movement. Also each lens would be scaled differently in terms of f-stops and amount of movement. There is no gaurantee what so ever on third party lenses, where they may have used the lever almost as an of / off switch, or something different depending on what suited thier production. As a result while perhaps better than nothing, exposure would not be what people have come to expect.
Now for the one they should do.
if you entered maximum aperture, then pentax could compensate for the non linearities of the viewing screen and metering system just as they do on KA lenses, and by pressing the green button, and using the difference in exposure between wide open metering and stopped down metering, make a very accurate corrected metering, as well as calculating the set F stop of the lens It would slow down the green button function a little, but because it could also calculate the preset aperture, P-TTL flash could work. I would love to see them do this.