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08-25-2015, 10:54 PM   #1
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Auto ISO with M lenses in M mode

I've noticed that the P Line button is disabled when Auto ISO is on in M mode. The shutter speed also changes depending on the ISO. Does that mean that light metering is automatically taken in this case? I took some photos and the exposure seems to be fine.

Thank you

08-25-2015, 10:56 PM   #2
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QuoteOriginally posted by farhaddad Quote
I've noticed that the P Line button is disabled when Auto ISO is on in M mode. The shutter speed also changes depending on the ISO. Does that mean that light metering is automatically taken in this case? I took some photos and the exposure seems to be fine.

Thank you
It works like TAv, so yes.

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08-25-2015, 11:03 PM   #3
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QuoteOriginally posted by Adam Quote
It works like TAv, so yes.
If thats the case, would it still work if I limit the ISO range from 100 - 200 for example?


Nevermind! I've just tried that. Perhaps this make M lenses more useful than I thought! Other than the metering mode, they're almost the same as A lenses, no?

Thank you for your help.

Last edited by farhaddad; 08-25-2015 at 11:20 PM.
08-25-2015, 11:37 PM   #4
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QuoteOriginally posted by farhaddad Quote
If thats the case, would it still work if I limit the ISO range from 100 - 200 for example?


Nevermind! I've just tried that. Perhaps this make M lenses more useful than I thought! Other than the metering mode, they're almost the same as A lenses, no?

Thank you for your help.
Well you still need to stop-down meter with them. The reading you'd get by default is based on the lens being wide-open.


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08-25-2015, 11:57 PM   #5
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I don't think the camera will stop down the aperture in any other mode than M, if using a a lens with aperture ring in any other position than A.
As when using auto-ISO in M-mode turn the mode into TAv-mode, which is probably why stop down metering don't work with auto-ISO in M-mode.

So it's only M-mode with manual ISO that will fully support manual lenses without A-position on aperture ring.
08-26-2015, 12:08 AM   #6
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QuoteOriginally posted by Adam Quote
Well you still need to stop-down meter with them. The reading you'd get by default is based on the lens being wide-open.
QuoteOriginally posted by Fogel70 Quote
I don't think the camera will stop down the aperture in any other mode than M, if using a a lens with aperture ring in any other position than A.
As when using auto-ISO in M-mode turn the mode into TAv-mode, which is probably why stop down metering don't work with auto-ISO in M-mode.

So it's only M-mode with manual ISO that will fully support manual lenses without A-position on aperture ring.
Oh okay! I got excited for a moment . Thank you for your helps.
08-26-2015, 02:31 AM   #7
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Yeah, the difference is that M series lenses will default to Av mode if you choose Auto ISO or any mode other than M (It will say Av on the LCD screen). In Av mode, M series lenses have constant auto-metering and will adjust shutter speed (or shutter speed and ISO, if auto-ISO is chosen), but only for wide open aperture, regardless of what is chosen on aperture ring. This can be useful if you shoot wide open. This behaviour is also useful if you are using fully manual lenses, like m42 or the K-mount of certain third party brands that has no aperture lever at all.
But for some lenses, shooting wide open is not the best choice. In those cases you will need to use M mode with a static ISO number, then you can use green button for the camera to stop down to the chosen aperture, meter, and adjust shutter speed.

Lenses with A on Aperture ring, like A series or modern Samyang lenses, will allow you to use Av mode normally, as well as P and other modes. The difference is that with these, the camera knows the aperture, so you can choose it on the camera body, as with DA lenses (or you can let the camera choose it automatically)
08-26-2015, 02:43 AM   #8
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QuoteOriginally posted by Na Horuk Quote
Yeah, the difference is that M series lenses will default to Av mode if you choose Auto ISO or any mode other than M (It will say Av on the LCD screen). In Av mode, M series lenses have constant auto-metering and will adjust shutter speed (or shutter speed and ISO, if auto-ISO is chosen), but only for wide open aperture, regardless of what is chosen on aperture ring. This can be useful if you shoot wide open. This behaviour is also useful if you are using fully manual lenses, like m42 or the K-mount of certain third party brands that has no aperture lever at all.
But for some lenses, shooting wide open is not the best choice. In those cases you will need to use M mode with a static ISO number, then you can use green button for the camera to stop down to the chosen aperture, meter, and adjust shutter speed.

Lenses with A on Aperture ring, like A series or modern Samyang lenses, will allow you to use Av mode normally, as well as P and other modes. The difference is that with these, the camera knows the aperture, so you can choose it on the camera body, as with DA lenses (or you can let the camera choose it automatically)
Thank you for explaining further. I was shooting wide open when I tried the Auto ISO feature and it didn't occur to me that it would be different for smaller apertures. The reason I got excited for a moment thinking that a manual lens could work like an A lens minus the in camera aperture control and the evaluative metering!

Again, thank you everyone for explaining.

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