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04-20-2012, 01:49 AM   #1
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K7 light meter is consistent in LV?

Hi all,

I´m trying out different settings on my K7 to be used with manual lenses like the Super-Tak 1.4/50 and the S-M-C 1.8/55 in M (w. Green B.) and in Av mode.
It´s annoying that the meter isn´t consistent. It´s not even consistent in it´s inconsistency but makes sudden ‘jumps‘ (for instance drastic increases as you open up the lens or groups from 1.4 - 2.8; 2.8 - 5.6; 5.6 - 11 etc.).

However I find that the metering is much more consistent in ‘Live view‘ than when using the optical view finder? Why is this?

04-20-2012, 02:16 AM   #2
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When not using LV, the light meter is somewhere in the optical path via the mirror (not sure where, somewhere near / in the viewfinder if I'm not mistaken as a split prism screen influences the metering).
When using LV, the camera uses the sensor to meter; mirror is up so it can't use the 'normal' meter.

Why the result is different, is basically a software function.
04-20-2012, 02:36 AM   #3
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QuoteOriginally posted by sterretje Quote
When not using LV, the light meter is somewhere in the optical path via the mirror (not sure where, somewhere near / in the viewfinder if I'm not mistaken as a split prism screen influences the metering).
When using LV, the camera uses the sensor to meter; mirror is up so it can't use the 'normal' meter.

Why the result is different, is basically a software function.

1. Thank´s. The mirror is up, but why is it more consistent? (It´s the same lens and the same software)

2. This is what I´m thinking too. But I don´t find that the inconsistencies change, as I change the settings in ‘High/Low‘, ‘Contrast‘, Contrast Highlight‘ etc. What happens is that you just ‘push‘ the problem around and about, up and down a scale? Hmm.

(Some geek out there with a patch to fix the software for old lenses?)
04-20-2012, 02:41 AM   #4
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It looks like the +/- EV changes the meter much more than just ‘stopping‘ up or down and also much more than changing the ISO does

04-20-2012, 05:29 AM   #5
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M lenses don't have auto aperture so you need to use stop-down metering, are you using that?
04-20-2012, 06:15 AM   #6
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I think both lenses are Takumars. at least, that's how I read the post.
04-20-2012, 06:22 AM   #7
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QuoteOriginally posted by jt_cph_dk Quote
the metering is much more consistent in ‘Live view‘ than when using the optical view finder? Why is this?
because in live view mode the metering is done off the sensor itself - the optical exposure meters that are used when the mirror is flipped down are behind the focusing screen - and if you are using an after-market focusing screen with focusing aids on it then that is most likely causing the erratic AE behaviour.

Last edited by Digitalis; 04-20-2012 at 06:30 AM.
04-21-2012, 03:54 AM   #8
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QuoteOriginally posted by Digitalis Quote
because in live view mode the metering is done off the sensor itself - the optical exposure meters that are used when the mirror is flipped down are behind the focusing screen - and if you are using an after-market focusing screen with focusing aids on it then that is most likely causing the erratic AE behaviour.
I´m using a Katz Eye focusing screen ‘Plus Split Prism w/Microprism Collar‘. Can that really be the cause? I´ll check out the Katz Eye sites Q&A pages.
Thank´s.

04-21-2012, 03:58 AM   #9
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QuoteOriginally posted by Anvh Quote
M lenses don't have auto aperture so you need to use stop-down metering, are you using that?
The current lenses in question are Takumars, but I also use K & M lenses and stop down.
Thank´s
04-21-2012, 04:03 AM   #10
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QuoteOriginally posted by Digitalis Quote
because in live view mode the metering is done off the sensor itself - the optical exposure meters that are used when the mirror is flipped down are behind the focusing screen - and if you are using an after-market focusing screen with focusing aids on it then that is most likely causing the erratic AE behaviour.
Each lens have it´s own effect on the meter? They don´t have similar profiles, but will produce different results, when I go through the aperture steps taking test shots.
04-21-2012, 07:01 AM   #11
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QuoteOriginally posted by jt_cph_dk Quote
I´m using a Katz Eye focusing screen ‘Plus Split Prism w/Microprism Collar‘. Can that really be the cause?
It most certainly is a contributing factor to your problems - there is a reason why pentax cameras all have the same standard screen when they are sold. Because the light meters are calibrated so then they can obtain a correct exposure reading off them. The split prism focusing screens are notorious for causing problems - especially with spot metering.
04-21-2012, 08:07 AM   #12
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You are certainly right

QuoteOriginally posted by Digitalis Quote
It most certainly is a contributing factor to your problems - there is a reason why pentax cameras all have the same standard screen when they are sold. Because the light meters are calibrated so then they can obtain a correct exposure reading off them. The split prism focusing screens are notorious for causing problems - especially with spot metering.
I just tested the S-M-C 1.8/55 on my *ist DS2, which has the original standard screen — and (set in M or Av) it meters quite consistently!

The split prism is really good for critical focus, so I´ll have to work around the inconsistency setting the +/-EV level to match the aperture and light then.

Thank´s
04-21-2012, 08:42 AM   #13
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Katz Eye Screen

I have a katz eye in my K7 and absolutely love it. However it does have an effect on the K7's metering. A bit of exposure compensation, around -2, usually takes care of it. Once in a while I may adjust that based on what I see in my histogram. However, the metering difference between live view and normal is pretty consistent assuming that I keep the spot on the same target all the time.

I also have a katz eye in my DL2 (particularly critical since the focus motor died quite some time ago) but it does not require any exposure compensation at all so you will probably need to mess around with your own camera until you find your own sweet spot.
04-22-2012, 01:13 AM   #14
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Maybe one day the moronic Pentax firmware programmers will realise that it would be useful to be able to store exposure calibration offsets linked to lens ID in the camera.
04-22-2012, 01:51 AM   #15
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QuoteOriginally posted by kh1234567890 Quote
Maybe one day the moronic Pentax firmware programmers will realise that it would be useful to be able to store exposure calibration offsets linked to lens ID in the camera.
I agree. And why not program all calibrations into the firmware directly, so we could just identify our lenses in a list? That would be a handy feature. Also it seems odd to me, that there are two meters. One for the view finder and one in the chip. Both are TTL and should be the same. What´s a meter doing on a chip (comparable to film)? At least they should be calibrated. DSLR is still only ‘crawling‘ and it looks ‘clumsy‘ to me. Thank´s
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