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12-20-2012, 04:05 PM   #1
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Manual Lenses, Green Button and Flash

The penny eventually dropped and I understand that when using a Manual exposure lens (i.e. one that has no "A" setting) I need to put the Exposure dial in M mode and before shooting I depress the green button in order for the camera to set the required shutter speed AND close the aperture blades to the required aperture.

That's fine - I get that now.

But tonight I managed to get myself further confused....

I've just got an SMC-M 40mm F2.8 traditional "pancake" lens and put it on the K-01. In artifical light I set the ISO to 1600 and did the Green button thing and that worked fine.

So I then decided to put my Flash (an old Chinon Auto-Thyristor flash that has done me sterling service on the Samsung GX-10 having checked the trigger voltage sometime ago) on the K-01. On the GX-10 I would set the camera to M Mode, ISO200 and F5.6 with shutter speed set to 1/180 and everything works a treat.

I setup the K-01 with this flash as close to my GX-10 settings (M-Mode, ISO200, F5.6 and set shutter speed to 1/160sec).

I then pressed green button to set the aperture blades to F5.6 - which it does, but in so doing it changes the shutter speed to around 1/4 sec due to available light.

I then changed the shutter speed back to 1/160sec.

I performed the Auto-Thyristor flash test which sets the amount of flash required and

Then take a photo.

All is well - exposure correct and depth of field looks correct.

Just to check. I reset the aperture to F2.8 on the lens, take another photo having repeated the process with the green button and shutter speed and it's over exposed (as expected) and depth of field is considerably narrowed.

I repeat the first test - same result as first time, but then take a number of photos of the scene without making any changes between the photos.

What I wasn't expecting - but this is good - is that the Aperture setting is obviously retained between the photos as the same depth of field is retained in all the shots.

Is this what others would have expected? I thought I would have to go through the green button thing between each shot. So I haven't worked out at what point it "looses" the aperture setting. I will see if I can work it out, but would be interested in others observations.

So ignoring the flash for a moment - I presume that once the green button has been used to set the aperture, you can override the shutter speed and retain the aperture setting between multiple shots in the same session.

Neil

12-20-2012, 04:17 PM   #2
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You don't have to keep pressing the green button, whatever the aperture ring is set to is where the aperture goes every time you take a shot. It is purely mechanical, when the lens is set to f5.6 and the camera releases the lever, it will go to f5.6 every time. You can do it yourself, with the lens unmounted, hold the lever and the lens stays wide open, release the lever and it goes wherever the aperture ring is set to. There is nothing for the camera to "forget", because the camera never knew what aperture you were at.

All the green button does is close down the aperture so it can get a reading on the light coming through the lens at the aperture you selected, it is only for metering. If you don't need to meter, you don't need to hit it. With a thyristor flash like that, there is little need to meter.
12-21-2012, 01:03 AM   #3
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QuoteOriginally posted by elliott Quote
You don't have to keep pressing the green button, whatever the aperture ring is set to is where the aperture goes every time you take a shot. It is purely mechanical, when the lens is set to f5.6 and the camera releases the lever, it will go to f5.6 every time. You can do it yourself, with the lens unmounted, hold the lever and the lens stays wide open, release the lever and it goes wherever the aperture ring is set to. There is nothing for the camera to "forget", because the camera never knew what aperture you were at.

All the green button does is close down the aperture so it can get a reading on the light coming through the lens at the aperture you selected, it is only for metering. If you don't need to meter, you don't need to hit it. With a thyristor flash like that, there is little need to meter.
Thanks for that. Having thought I'd got my head round the Green Button thing, I clearly hadn't. I had believed that it was the Green Button that "released" the lever to allow the correct Aperture to be set.

So as I now think I understand it:

In anything other than M Mode the camera holds the aperture open until the shutter is pressed, but with a manual aperture (as opposed to a "A" ) lens, the aperture stays fully open even when the shutter is depressed (thus causing the narrow depth of field if the lens is used in Av or Tv mode).

When in M Mode the aperture is ALWAYS released when the shutter is depressed. But is also released when the Green Button is pressed so that the correct shutter speed can be determined.

Thus - when using my Auto Tyristor flash - I just set the ISO/Shutter Speed on camera and Aperture on lens as per the Flash requirements and away I go. No need to use the Green Button at all.

Do I understand it now?
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