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06-05-2013, 12:42 PM   #16
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QuoteOriginally posted by PiDicus Rex Quote
Steve, that's really not an answer to my question, it's a comment on a limitation that the lens will have if modified and used.
...and that should at least partially answer your question.

The topic of attempted modification of non-A contact lenses comes up regularly on this forum and the standard answer is that it is not recommended due to the non-linearity issue. You are correct that this "limitation" only applies at other than maximum aperture, though I find it strange that you would assume that all respondents would know that you shoot your video exclusively wide-open.

Based on your comment, it appears that you already know the answer. (Logic is wonderful, eh?) If the proper contacts are present, the body will identify the lens as KA.


Steve

06-06-2013, 07:51 AM   #17
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Here's my question again....
QuoteQuote:
Has anyone used this sort of modification when shooting video - I'm curious as to if it would help to prevent the auto-gain ramping of a K-01 when used with KM lenses.
Before typing any other answer, ask this, what in what you have replied so far answers this question?

You've addressed how the IRIS works, and then whether the camera will identify the lens as KA, but nothing about what the question asked.
06-06-2013, 01:32 PM   #18
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QuoteOriginally posted by PiDicus Rex Quote
Here's my question again....


Before typing any other answer, ask this, what in what you have replied so far answers this question?

You've addressed how the IRIS works, and then whether the camera will identify the lens as KA, but nothing about what the question asked.
You may get more traction if post a fresh thread on the Pentax Mirrorless section of this site.


Steve
06-06-2013, 02:03 PM   #19
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I guess the issue will be different for video than normal shooting. For normal shooting, the camera makes calculations which are based upon knowing how much the shutter will stop down, and I the case of a modified lens, this is a crap shoot, but in video mode, it meters directly based upon the sensor and actual light.

I this case it is likely to get the lighting right, but get the desired aperture setting wrong, from the in body aperture control

09-13-2013, 04:07 PM   #20
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I just did this to my k5 and my k20d(did this one first) I'm not going to go about painting insulation points on all my lenses (the lens locking mechanism tends to scrape the paint off and may end up in my lens or in the camera).
A bare metal lens reads as f1:1.2-f22 so I set my ev steps to 1/2 steps and it makes it easier to keep track of aperture'
. It will be more inaccurate if your lens has more or less than 8.5full stops

Last edited by Sliver-Surfer; 12-22-2013 at 08:58 AM.
09-13-2013, 11:13 PM   #21
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QuoteOriginally posted by Sliver-Surfer Quote
I just did this to my k5 and my k20d(did this one first) I'm not going to go about painting insulation points on all my lenses (the lens locking mechanism tends to scrape the paint off and may end up in my lens or in the camera).
A bare metal lens reads as f1:1.2-f22 so I set my ev steps to 1/2 steps and underexpose one full step for every full stop my lenses aperture ring begins at above f1.2.
so my 2.8/28mm would be set at -2.5ev. It will be more inaccurate if your lens has more or less than 8.5full stops
But the question still remains, what is the exposure accuracy? When I did my modification in 2007, I tested with a K10, as that was what was available, and measured exposure accuracy, and flash accuracy using a uniform target (grey block wall) and measured the greyscale values at each aperture setting .

I know from a practical point, all of the mods discussed above will give some appearance of exposure control, specifically for flash, but what I found was that the accuracy was so far off, and changed as a function of shooting aperture, that it made it no better than the errors you get with an M or K lens un modified. For flash, when you consider really how easy manual flash calculations are , the accuracy with a quick manual flash calculation using 15 meters for the GN at ISO 100 for the body flash is much better than a modified lens can give so I just gave up. Nothing I have seen posted here in the past 6 years has changed this opinion,
09-14-2013, 06:02 PM   #22
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It's not always accurate but it costs nothing takes 60 seconds to do and ads a very handy tool thats quite usefull in certain circumstances
12-22-2013, 07:29 AM   #23
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Does anyone know if the Rikenon "P" lenses have KA-style aperture lever action? Seems like they should considering 3rd party manufacturers had P(A) lenses...

12-22-2013, 08:46 AM   #24
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Hi Jeff,
If you mean "Does a Rikenon- P lens in non-P mode work on a K-mount film camera which has the the mechanical aperture signal lever?"

Yes, I have been using a Rikenon-P zoom lens like that for many years and it works well, just like the Pentax-M lenses and the Pentax-A lenses in non-A setting,
and the Rikenon XR lenses and any other old type 3rd party K mount lens.

Also all these lenses work OK like that on Pentax dslrs including the K-01, when the camera is in M mode and the stop down button is pressed to meter.
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