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03-30-2012, 11:40 PM   #1
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K-7 exposure and manual lenses, better then K10D?

The K10D was never particularly good at reading a correct exposure with manual aperture lenses (Pentax-M, Pentax-K, M42 etc).

This was something that drives me nuts with my K10D. Generally, I get my exposure through a trial and error process.

So how does the K-7 fair with lenses that require aperture coupling? Is it any better at "green button metering" then the K10D?

03-31-2012, 04:39 AM   #2
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K7 has 77 segments to exposure....so reading a quite correct exposure...I'm sure about it...K20d is too.I'm using K7...It's a best choice in this time
03-31-2012, 06:08 AM   #3
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Hi, KungPOW.
I have a K 200D and a K-5. Both are excellent for working with SMC-M and M-42 lenses - either via the green button, or by taking a reading using the depth-of-field preview. It surprises me to hear that you have problems in this respect with the K-10. What can be misleading is that the cameras will allow you to use P, SV, AV, and TV modes with these old lenses you only get AV, and that at full aperture. This also happens with A-, F-, and FA-lenses when you move the aperture ring off the "A" setting. The handbook does state this, and also that such exposures can be off-target.
With any lenses other than the A-, F-, FA-, FAJ- or thereafter - that is to say any lenses which require you to set the aperture ring, i.e. SMC-, SMC-M, M-42, or some specialised lenses like the soft-focus or shift lenses - you must use manual mode to get correct exposures. It's no great hassel, as the green button is truly the next best thing to automatic exposure-setting - or you take a "stopped-down" reading, like in the good old days.
Hope this helps!
Chanel.
03-31-2012, 08:23 AM   #4
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Thanks for the answers guys.

But the K10D has a known metering issue with non-electronic contact lenses. It is not a user error issue.

I should have searched a little harder last night, because this morning I was able to find this thread that discusses the topic.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/124627-k-5-met...-m-lenses.html

I had forgotten that Lowell had worked out the exposure charts for various camera/lens combos.

04-01-2012, 02:08 AM   #5
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Hi, KungPOW. I had a look at that thread. I have the impression that the participants had not read their handbooks!

Reliable exposure-metering with K-, M-, and M-42 lenses (and A-, F-, FA-lenses with the aperture ring in any other position than "A") is available only in manual mode.

I have experimented with M-42 lenses in AV-mode and had reliable exposures at +2 stops compensation. (This does not work with K- and M- lenses, as the aperture remains wide open, as stated in the handbook.) However I see no point in doing this when manual mode works perfectly and I have instant and reliable exposure-settings with the green button.

Greetings,

Chanel.
04-01-2012, 10:49 AM   #6
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Chanel,

Take your K10D/K20D with am M lens on the front.

Find a blank featureless wall to use to set the exposure.

In manual mode, using just the green button for stop down metering, shoot a series of test shots of the wall, only changing the aperture for each shot.

Now look at the histograms for the series. You should see that the histogram peak moves from shot to shot.

Now change the lens to an FA lens. Do the same experiment. The histogram peak will not move(much).

This is the exposure problem I am talking about.
04-02-2012, 02:34 PM   #7
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Thanks, KungPOW.

I've done a quick test along the lines you recommend, using my K-5, my K 200D and the following lenses: SMC M Macro 4/50, SMC 1.4/50, and SMC FA 1.4/50.

You are quite right, there are inconsistencies in the results, and as you suspected, more so with the older model than with the K-5, and more so with the older lenses.

However, I must also say that within the range of f:5.6 to f:11/16 both bodies are spot-on with all lenses.

It seems to be a matter of the reciprocity of the "stopped-down" metering at extreme apertures. I thought it might possibly (at least at the lower end of the aperture range) have something to do with stray light entering via the eye-piece, but I repeated some of the tests with the ocular covered, and while that may have some influence, it certainly does not explain everything.

However, there is no method of exposure reading and/or setting (or AF system for that matter) that is perfect in every respect in every situation, and while I certainly don't intend to lose too much sleep over the matter, I shall be interested to follow your further findings on the subject.

Greetings,

Chanel.
04-03-2012, 03:51 AM   #8
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QuoteOriginally posted by Chanel Quote
Hi, KungPOW. I had a look at that thread. I have the impression that the participants had not read their handbooks!

Reliable exposure-metering with K-, M-, and M-42 lenses (and A-, F-, FA-lenses with the aperture ring in any other position than "A") is available only in manual mode.

I have experimented with M-42 lenses in AV-mode and had reliable exposures at +2 stops compensation. (This does not work with K- and M- lenses, as the aperture remains wide open, as stated in the handbook.) However I see no point in doing this when manual mode works perfectly and I have instant and reliable exposure-settings with the green button.

Greetings,

Chanel.
I am not sue what you mean by your comment here. The chart that I put forward was done using the manual mode and green button. It shows the non linearity of metering with different camera models, and or combinations of focusing screens. The K10D is arguably the worst performing body, the *istD was the best, until the release of the K5D which appears to be equal to the original *istD.

04-03-2012, 03:53 AM   #9
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QuoteOriginally posted by Chanel Quote
Thanks, KungPOW.

I've done a quick test along the lines you recommend, using my K-5, my K 200D and the following lenses: SMC M Macro 4/50, SMC 1.4/50, and SMC FA 1.4/50.

You are quite right, there are inconsistencies in the results, and as you suspected, more so with the older model than with the K-5, and more so with the older lenses.

However, I must also say that within the range of f:5.6 to f:11/16 both bodies are spot-on with all lenses.

It seems to be a matter of the reciprocity of the "stopped-down" metering at extreme apertures. I thought it might possibly (at least at the lower end of the aperture range) have something to do with stray light entering via the eye-piece, but I repeated some of the tests with the ocular covered, and while that may have some influence, it certainly does not explain everything.

However, there is no method of exposure reading and/or setting (or AF system for that matter) that is perfect in every respect in every situation, and while I certainly don't intend to lose too much sleep over the matter, I shall be interested to follow your further findings on the subject.

Greetings,

Chanel.
With a K5 and the relatively good performance of the metering there is not too mush to worry about. The performance like the *istD is minimal, relatively consistent and over the enti range is less than one stop, and typically people don't notice. The K10D is another story
04-03-2012, 11:41 PM   #10
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I used M lenses all the time with my K100D. They worked well, no real issues with exposure.

I knew about the K10D exposure issue before I got the camera, but it was far worse then I had expected. The result being, that I stopped using M lenses on the K10D.

Now with the prices of K-7's (used) dropping, I was considering changing bodies to make use of my M lenses on a digital again.

I'm not sure it is worth it.

--------------------

Thanks for your work with regard to this issue Lowell.
04-04-2012, 04:15 AM   #11
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The k 7 meters much better than the K10 that is for sure, and is ok until you get to small apertures

Look at my chart and decide for youtself
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