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03-06-2022, 12:58 AM   #1
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Green button metering

I am currently using centre weighted but does one mode work better than the others with the green button?

03-06-2022, 01:57 AM - 3 Likes   #2
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QuoteOriginally posted by Cerebum Quote
I am currently using centre weighted but does one mode work better than the others with the green button?
Centre weighted metering is the forerunner of Multi segment matrix metering. CW meters the whole scene but gives more weighting to the centre (ergo the name). Matrix metering is more sophisticated and for very high contrast scenes as well as very dark/light scenes will usually do a better job of exposing for the central subject. For most general scenes they are as good as each other. Spot metering is very specific and is often used to get an average reading by the photographer. Spot metering is also useful when using ND grads

The green button in Manual exposure can be used with all three metering modes with a modern lens. If you are using an older lens like a "K" or M series, you are limited to CW or spot only.
03-06-2022, 02:14 AM   #3
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QuoteOriginally posted by pschlute Quote
Centre weighted metering is the forerunner of Multi segment matrix metering. CW meters the whole scene but gives more weighting to the centre (ergo the name). Matrix metering is more sophisticated and for very high contrast scenes as well as very dark/light scenes will usually do a better job of exposing for the central subject. For most general scenes they are as good as each other. Spot metering is very specific and is often used to get an average reading by the photographer. Spot metering is also useful when using ND grads

The green button in Manual exposure can be used with all three metering modes with a modern lens. If you are using an older lens like a "K" or M series, you are limited to CW or spot only.
Thanks I need to try matrix. I have been using spot fairly exclusively for years in this case, the green button is looking after an M42, so I don't have the fancy options but your answer reinforces what I was thinking looks like I got it right for once
03-06-2022, 07:29 AM - 1 Like   #4
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QuoteOriginally posted by Cerebum Quote
in this case, the green button is looking after an M42
Can you not simply use Av mode with M42 lens. That is what I do.

03-06-2022, 09:43 AM   #5
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QuoteOriginally posted by pschlute Quote
Can you not simply use Av mode with M42 lens. That is what I do.
Theoretically, this should work, but, in my experience, and probably only with some lenses and/or some cameras, there can be a tendency to over-expose.
Don't ask me why, I just know it has happened to me in Av sometimes, but not in Manual … so I stick with the Green Button
Try Av, certainly, and if it works for you "happy days"
03-06-2022, 10:16 AM   #6
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QuoteOriginally posted by kypfer Quote
Theoretically, this should work, but, in my experience, and probably only with some lenses and/or some cameras, there can be a tendency to over-expose.
Don't ask me why, I just know it has happened to me in Av sometimes, but not in Manual … so I stick with the Green Button
Try Av, certainly, and if it works for you "happy days"
It should be the same issue in both AV and M mode, although I seem to recall on some bodies there is potentially an offset of a stop or two between the two modes. I don’t know why.

There can also be errors due to the viewing screen and the non linearity of the metering. The camera really needs to know the FStop of the lens when you are metering. The K10 was the worst but it is not the only camera with such errors
03-06-2022, 11:26 AM   #7
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QuoteOriginally posted by Lowell Goudge Quote
The K10 was the worst
Tell me about it ! My manual lenses went into hibernation from K10D days until the K-1 came out

03-06-2022, 02:36 PM   #8
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QuoteOriginally posted by pschlute Quote
Can you not simply use Av mode with M42 lens. That is what I do.
I use to use av with M42s but then @pepperberryfarm introduced me to the green button and I never looked back. Av works nicely but I find the green button to be generally more reliable :
03-06-2022, 03:30 PM   #9
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QuoteOriginally posted by kypfer Quote
Theoretically, this should work, but, in my experience, and probably only with some lenses and/or some cameras, there can be a tendency to over-expose.
I have never tested it out*, but believe your observations are traceable to incremental improvements to M mode stop-down metering starting with the K-7.** Whether such are applied with manual aperture lenses in Av mode is hard to say.

BTW...You may have have noticed that stop-down metering with your *ist D is spot-on. That is because its screen is old school.


Steve

* I could do it right now, but am too lazy.

** The theory here is a bit convoluted, but relates to the stock focus screen's brightness not being linear to the lens' physical aperture. This may be demonstrated by observing the viewfinder brightness while stopping down a manual aperture lens. With an f/2 lens mounted, brightness will be the same at f/2.0, f/2.8, and f/4.0 (even to f/5.6 with some subjects). Open-aperture metering (e.g. Av mode) allows the camera to compensate for the screen, but without knowing the set aperture, such compensation will not be possible. I don't know how corrections are applied for stop-down metering in M mode, but they appear to work pretty well. FWIW, I generally do stop-down metering in live view for greater accuracy.

Last edited by stevebrot; 03-06-2022 at 03:50 PM.
03-06-2022, 05:59 PM   #10
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Av mode on M and K series, and I assume any lens that does not have aperture feed back, just holds the lens wide open.
03-07-2022, 11:12 AM   #11
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Electrical contacts are needed for matrix metering - the camera needs to know the min and max aperture range of the lens. K, M and screwmount lenses don't supply this information.
03-08-2022, 03:14 AM   #12
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QuoteOriginally posted by Riggomatic Quote
Av mode on M and K series, and I assume any lens that does not have aperture feed back, just holds the lens wide open.
"K" and M lenses do just that in Av mode...shoot wide open. Exposure is correct though.

There is one "K" lens that will work in Av mode and that is the 85mm 2.2 SOFT lens. This is because there is no linkage to hold open the aperture, so it behaves like a M42.
10-05-2022, 02:00 AM   #13
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Is it possible to set a fixed exposure correction when using the green button?

I couldn't find this on my K-X in any case. I combine it with exposure bracketing for slight exposure corrections, but when I use filters I always need to correct a few steps after pressing the green button by turning the shutter-speed dial .

Last edited by pimpim; 10-05-2022 at 02:06 AM.
10-05-2022, 04:18 AM   #14
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QuoteOriginally posted by pimpim Quote
Is it possible to set a fixed exposure correction when using the green button?
I couldn't find this on my K-X in any case. I combine it with exposure bracketing for slight exposure corrections, but when I use filters I always need to correct a few steps after pressing the green button by turning the shutter-speed dial .
I don't have a K-x specifically, but, in general, assuming the use of the Green Button in manual mode, I don't believe so.
I've taken to using Digital Preview with histogram to confirm things after using the Green Button to "get it in the ball park" … takes a few seconds more, but the result is usually worth the effort
Unfortunately, having just skimmed the K-x handbook, it would seem that the K-x has limited functionality options in this respect, the Green Button having to be assigned to one function or the other, so it might not be as easy with this model as with some others
10-05-2022, 04:29 AM   #15
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Thanks for checking! I have a few newer Pentax cameras luckily But I set up my K-X for manual use with a split screen replacement etc. I am not the most dexterous person so I think i scratched the original split screen and don't want to mess with that on other cameras anymore

I do find that the catch-in-focus works like a charm, so maybe I don't even need the split screen and will use something newer like a K-5 with OME53 for manual lenses.

I will look around a bit more if the green button can do exposure compensation on e.g. the K-5
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