K5/7 and M lenses


Link Posted 10/10/2010 - 13:04
While at SRS yesterday contemplating swapping my *ist D for something newer I asked how it metered with an M lens; the *ist D has a green button which sets the correct exposure before pressing the shutter release. Not difficult but not very quick either. I couldn't see a green button on the K5.

The demonstrator said he wasn't sure but thought you just put a K5 or K7 on Manual and then pressed the shutter as normal. That would be nice but I find it hard to believe; if it was that easy I'd keep all my M lenses instead of replacing some.

Are M lenses easy to operate on a new body?


Link Posted 10/10/2010 - 13:43
On the assumption that the K-5 is the same as the K-7, you have two options - both of which are used when the camera is in M mode (Av will not enable you to stop the lens down, even if you change the aperture ring).

Option one = green button, which is on the rear of the camera.

Option two = stop down by twisting the on/off/depth of field preview switch around the collar of the shutter, which will turn on the exposure meter in the viewfinder and enable you to change aperture (on lens) or shutter speed (using e-dial) until you have chosen the exposure you want. In other words, doing it this way enables stop-down metering, and by using the viewfinder display you can also dial in the exposure compensation that you think you might need.

I prefer option two, because once you've got used to it, it is very quick and easy to choose the aperture you want to use in advance, stop the camera down while you are looking through the viewfinder and then manually choose the correct shutter speed before shooting.

I can't comment about the istD, but compared to K100D and K20D, I find the metering in the K-7 generally to be more accurate with M lenses.


Link Posted 10/10/2010 - 14:53
Thank you Jon, looks like I missed the green button on the back (it's on the top on an *istD), and M lenses should remain usable, though I think I will check the trade in price to see if I can afford any upgrades.

Most of the time my *ist D metered well enough via the green button but occasionally the exposure accuracy was poor, I always assumed I had done something silly but maybe I can blame the camera after all.


Link Posted 10/10/2010 - 22:39
I think you didn't look good enough for the green button
Like you said it's on the back.


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
Last Edited by Anvh on 10/10/2010 - 22:40


Link Posted 05/01/2011 - 13:26
I thought today I'd see how my old M Lenses would work with my new K-5 having sometimes found quite an exposure discrepancy when stopping these lenses down on my older Pentax/Samsung DSLR bodies (K200D, GX-20, K-m).

I set the camera to M (having found that Av did nothing) and pressed the green button and pleasingly found it stopped the lens down briefly to take an exposure reading and right across the range of f numbers exposure was consistent and good and according to the histograms produced perhaps even better than the 18-55 that came with the camera. That was with both an M 50mm f1.4 and an M 200mm f4.

I always thought it odd that using older M and K lenses never worked as expected previously. If anyone has old M lenses and wondering whether to go for the K-5 or an older model to get the best out of them, then the K-5 would seem to be the Pentax of choice (I've not tried a K-7.)

Having got the lenses working fine I thought I'd check in the camera manual for the official method of using them. I couldn't even find a mention of this and no reference to the green button providing this function unless I've missed it somehow. Why would Pentax omit this information?
John K
Last Edited by JAK on 05/01/2011 - 13:46


Link Posted 05/01/2011 - 16:43
JAK wrote:
...Why would Pentax omit this information?

Because in order to stay in business they want you to buy new lenses rather than old ones (on which they receive no cut).
Joining the Q


Link Posted 05/01/2011 - 17:00
hefty1 wrote:
JAK wrote:
...Why would Pentax omit this information?

Because in order to stay in business they want you to buy new lenses rather than old ones (on which they receive no cut).

I appreciate that's tongue in cheek but as Pentax use the fact that their older lenses are compatible with the new cameras is a selling point a little guidance on the matter in the camera manual wouldn't have gone amiss!

It must have been one of the most asked 'how to' questions about Pentax DSLRs so really should have had a mention.

John K


Link Posted 05/01/2011 - 17:16
It does have a mention, but it's a bit vague I think. Not sure whether or not that's something that was lost in the English translation.
Best regards, John
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