Auto ISO selection with manual lens?

mjp29 · 01-29-2021, 08:06 AM

Originally posted by pschlute

When your manual K-mount lens is on the camera, the aperture will be wide open. In Manual mode the camera will stop the lens down on capture to what you have selected on the lens aperture ring. If you try and use Av mode it will remain wide open irrespective of where the aperture ring is set.

M42 lenses are different. What lens are you actually using.

Asahi Pentax m-100mm 1:4

---------- Post added 01-29-21 at 08:08 AM ----------

I wander if, when pressing the green button, the k-r camera looks at the set iso and takes it into consideration when determining the shutter speed/exposure.
Probably not.
Referring to k-r camera.

pschlute · 01-29-2021, 01:31 PM

Originally posted by mjp29

Asahi Pentax m-100mm 1:4

Yes that works for stop down metering as I and others have explained.

Originally posted by mjp29

I wander if, when pressing the green button, the k-r camera looks at the set iso and takes it into consideration when determining the shutter speed/exposure.
Probably not.

Probably YES. How else do you expect it to calculate an exposure ?Without knowing the ISO, a light meter is unable to make the calculation.

mjp29 · 01-29-2021, 01:35 PM

ok, thanks

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01-29-2021, 08:06 AM	#16
mjp29 Junior Member Join Date: Dec 2013 Posts: 32 Original Poster	Originally posted by pschlute When your manual K-mount lens is on the camera, the aperture will be wide open. In Manual mode the camera will stop the lens down on capture to what you have selected on the lens aperture ring. If you try and use Av mode it will remain wide open irrespective of where the aperture ring is set. M42 lenses are different. What lens are you actually using. Asahi Pentax m-100mm 1:4 ---------- Post added 01-29-21 at 08:08 AM ---------- I wander if, when pressing the green button, the k-r camera looks at the set iso and takes it into consideration when determining the shutter speed/exposure. Probably not. Referring to k-r camera.

01-29-2021, 01:31 PM	#17
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,217	Originally posted by mjp29 Asahi Pentax m-100mm 1:4 Yes that works for stop down metering as I and others have explained. Originally posted by mjp29 I wander if, when pressing the green button, the k-r camera looks at the set iso and takes it into consideration when determining the shutter speed/exposure. Probably not. Probably YES. How else do you expect it to calculate an exposure ?Without knowing the ISO, a light meter is unable to make the calculation.

01-29-2021, 01:35 PM	#18
mjp29 Junior Member Join Date: Dec 2013 Posts: 32 Original Poster	ok, thanks