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K100D with M42 and Av mode
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PostPosted: Sat Oct 01, 2011 11:03 am    Post subject: K100D with M42 and Av mode Reply with quote
Ok, hopefully this will be the last silly question about the K100D Embarassed

On the *ist D, I really enjoyed being able to use my M42 preset lenses in Av (aperture priority) mode. It make it all so delightfully quick and easy. In M (manual) mode, it was a schlepp (focus, stop-down, meter, shoot) and I missed a few good shots of fast moving subjects.

I notice that on the K100D, the camera under-exposes by two or three stops in Av mode.

Is there a way to make the K100D behave like the *ist D in Av mode, or am I stuck with it in M mode only on this camera?

I ask as I much prefer the *ist way of doing things, and I like my old preset lenses the most. I was planning to sell the K mount lenses and stick to the old stuff, to save the constant fitting and removal of the M42 adaptor.

Thanks for your wisdom Cool


PostPosted: Sat Oct 01, 2011 11:36 am    Post subject: Reply with quote
Try shorting the rightmost contact on the mount with a piece of aluminium foil.


PostPosted: Sat Oct 01, 2011 1:44 pm    Post subject: Reply with quote
Ok, I just tried that. I can't make the foil stay in lace when I screw the lens on Confused

...but then I read the manual Embarassed and I can input +1.5 EV in Av mode. It seems to stay there even after power off. In manul mode the +1.5 EV doesn't affect it, and when I put M42 and switch to Av, it is there. Perfect Cool

The moral of the story? I need to be less lazy and RTFM Embarassed


PostPosted: Sat Oct 01, 2011 1:54 pm    Post subject: Reply with quote
Graham does the K100D really underexpose 1.5 stops at all apertures? I thought that the inaccuracy differs depending on the aperture chosen.
After I 'upgraded' from *istDs to K-x I resigned to using M mode + pressing the green button...should give the foil a try, or do the same like you..but as I said, I strongly believe that if and how much metering is off in A mode depends on aperture chosen
So far, if I want to avoid having to press the green button I simply leave the shutter speed where it was at the last, well exposed photo, resp. give the wheel a turn to correspondingly adjust the shutter speed in case I changed aperture or angle of view to a brighter or darker scene.

Last edited by kuuan on Sat Oct 01, 2011 1:59 pm; edited 1 time in total


PostPosted: Sat Oct 01, 2011 1:57 pm    Post subject: Reply with quote
kuuan wrote:
Graham does the K100D really underexpose 1.5 stops at all apertures? I thought that the inaccuracy differs depending on the aperture chosen.
After I 'upgraded' from *istDs to K-x I resigned to using M mode + pressing the green button...should give the foil a try, or do the same like you..but as I said, I strongly believe that if and how much metering is off in A mode depends on aperture chosen


I noticed the same thing when I upgraded from the D to the Kx: metering with M42 lenses was off, but it depended on apertures. Wider apertures are more off.

The foil trick makes the camera believe that a K lens is mounted, and should give better results. The green button is best, since it stops down when metering.


PostPosted: Sat Oct 01, 2011 2:03 pm    Post subject: Reply with quote
kuuan wrote:
Graham does the K100D really underexpose 1.5 stops at all apertures? I thought that the inaccuracy differs depending on the aperture chosen.
After I 'upgraded' from *istDs to K-x I resigned to using M mode + pressing the green button...should give the foil a try, or do the same like you..but as I said, I strongly believe that if and how much metering is off in A mode depends on aperture chosen

With plain K-mount lenses, M mode works perfectly. Av mode doesn't work as you can't stop-down to meter.

With M42 lenses, M mode works perfectly by pressing the button at the chosen aperture.

But with M42 and pre-set lenses, in Av mode, it is off by a constant 1.5 EV. I dod some tests and it was quite unirform across the aperture range, certainly enough for adding +1.5 for most situations.

KA mount lenses work perfectly in Av mode.

At least, that's how my camera is.


PostPosted: Sat Oct 01, 2011 2:05 pm    Post subject: Reply with quote
...my next job today is to remove the paint/anodising from one of my M42 preset lenses so that the contacts short out and I can use shake reduction. It will be interesting to see if that solves the metering problem too Cool


PostPosted: Sat Oct 01, 2011 2:06 pm    Post subject: Reply with quote
GrahamNR17 wrote:
...my next job today is to remove the paint/anodising from one of my M42 preset lenses so that the contacts short out and I can use shake reduction. It will be interesting to see if that solves the metering problem too Cool


Uhm, fold a square of kitchen alu foil until it's the right thickness, and make it so it's a small bar shaped thing that you can hold with two fingers while screwing the lens. Much easier than removing paint.


PostPosted: Sat Oct 01, 2011 2:08 pm    Post subject: Reply with quote
To get shake reduction with your preset lens I believe it is not necessary to remove the paint on it's mount, on the K100D it should work with any lens


PostPosted: Sat Oct 01, 2011 2:12 pm    Post subject: Reply with quote
kuuan wrote:
To get shake reduction with your preset lens I believe it is not necessary to remove the paint on it's mount, on the K100D it should work with any lens

Alas that is not what I find. When I put a lens on with black-painted T-2 mount, shake reduction symbol has a cross through it, but with a T-2 that I scraped the paint off, the SR works Confused


PostPosted: Sat Oct 01, 2011 2:47 pm    Post subject: Reply with quote
Graham, you've probably made these two menu custom settings already, but it's worth asking:

Set the Using Aperture Ring to "Permitted" (p.188 in the manual)

Set the Preview Method to "Optical" (p. 153)

There is no green button on the K100D is there? This function is accessed by turning the power-on switch to Preview mode, assuming the two setting mentioned above have been made. Of course, stop-down only works with K mount lenses and later, so presets and auto lenses have to be stopped down manually.

The manual states that the exposure is likely to be incorrect with non-A mount lenses, so the electrical contacts must have something to do with this. It's definitely worth experimenting with shorting them out. I don't see any reason why pre-set lenses should be any different to auto M42 lenses with an A-M switch.


PostPosted: Sat Oct 01, 2011 3:00 pm    Post subject: Reply with quote
peterqd wrote:
Graham, you've probably made these two menu custom settings already, but it's worth asking:

Set the Using Aperture Ring to "Permitted" (p.188 in the manual)

Set the Preview Method to "Optical" (p. 153)

There is no green button on the K100D is there? This function is accessed by turning the power-on switch to Preview mode, assuming the two setting mentioned above have been made. Of course, stop-down only works with K mount lenses and later, so presets and auto lenses have to be stopped down manually.

The manual states that the exposure is likely to be incorrect with non-A mount lenses, so the electrical contacts must have something to do with this. It's definitely worth experimenting with shorting them out. I don't see any reason why pre-set lenses should be any different to auto M42 lenses with an A-M switch.

No, no green button. Sorry for the confusion, I just still refer to it as that. It's actually the AE-L button that does the metering in Manual mode.

You're right, there is no difference between M42 preset or A/M style. Both still under-expose by 1.5 stops in Av mode.

I've now filed off the black paint on one of the lenses and am going to give it a try and see what, if any, difference it's made.


PostPosted: Sat Oct 01, 2011 3:02 pm    Post subject: Reply with quote
Ludo is a genius Cool Shorting the pins solves the problem Very Happy

My method, as mentioned above, is to remove the paint/black anodising from a small area of the mount as the foil wasn't staying in place.

Exposure in both manual and AV now match perfectly Cool


PostPosted: Sat Oct 01, 2011 3:15 pm    Post subject: Reply with quote
Although I never tried this, I've seen instructions for bending a bit of uninsulated wire to shape and hooking it between lens and mount - it stays put better than foil


PostPosted: Sun Oct 02, 2011 1:03 am    Post subject: Reply with quote
GrahamNR17 wrote:
kuuan wrote:
To get shake reduction with your preset lens I believe it is not necessary to remove the paint on it's mount, on the K100D it should work with any lens

Alas that is not what I find. When I put a lens on with black-painted T-2 mount, shake reduction symbol has a cross through it, but with a T-2 that I scraped the paint off, the SR works Confused


I don't have any T-mount but quite a few small, old lenses, also presets of which I have been quite sure that some don't shorten the contacts. Will have to confirm this, as I have not encountered, with any lens yet, shake reduction not working.

GrahamNR17 wrote:
Ludo is a genius Cool Shorting the pins solves the problem Very Happy

My method, as mentioned above, is to remove the paint/black anodising from a small area of the mount as the foil wasn't staying in place.

Exposure in both manual and AV now match perfectly Cool


great to know! I must try this out too, thank you very much for the tip Ludo.


PostPosted: Sun Oct 02, 2011 5:52 am    Post subject: Reply with quote
GrahamNR17 wrote:
Ludo is a genius Shorting the pins solves the problem


kuuan wrote:
great to know! I must try this out too, thank you very much for the tip Ludo.


It's not like I figured it out by myself, I read it somewhere on pentaxforums a couple of years ago. Smile

Glad it works for you too.


PostPosted: Sun Oct 02, 2011 10:13 am    Post subject: Reply with quote
ludoo wrote:
GrahamNR17 wrote:
Ludo is a genius Shorting the pins solves the problem


kuuan wrote:
great to know! I must try this out too, thank you very much for the tip Ludo.


It's not like I figured it out by myself, I read it somewhere on pentaxforums a couple of years ago. Smile

Glad it works for you too.


so did I
and I also remember that some reported problems related with it, which were they?
anyway, these scared me away then and since I never have felt the need to try it out. Wink now I should!


PostPosted: Wed Oct 05, 2011 3:01 am    Post subject: Reply with quote
I have been using the K100D since 2007 with variable +EV for the AV mode.
Does not seem to be a big problem. I suggest you always take a test shot when changing lighting conditions.

The same thing happens with the K-x
Also no big problem.


PostPosted: Wed Oct 05, 2011 2:10 pm    Post subject: Reply with quote
thank you very much Ludoo for your tip, Jussi and Luisalegria for your additional input.
who knows why it has taken me so long: just now tried out the shortcutting with a 'foil' and in my first trials AV mode exposed even a tad better than M mode and pressing the 'green' button. Great! I already had forgotten it, but now I remember how annoyed I was having to press the green button after upgrading from the *ist. Smile
I must find a way now to make a more stable contact than with a foil, will try some wires as suggested by Nesster.

best regards,
Andreas
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