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02-07-2016, 06:47 PM   #16
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Hi,

I'm still confused about Av (or Av is not working for me), with full manual (like an M42) lens.

If I put the mode to Av, I thought all I had to do was leave the lens wide open, e.g., with the 28mm Soligor I set it to f2.8, and put the mode to Av. Whether or not I hit the green button, and then shoot, it looks like it's coming in underexposed (too dark).

Can someone explain how I should use Av with such an manual lens?

Thanks,
Jim

02-07-2016, 07:35 PM   #17
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With a M42 lens (fully manual) lens, you set the fstop and take the picture in AV mode. If you set it at wide open it meters wide open and exposure should be OK. If you set it closed down--make sure the lens is closed down (it may have a switch to set in manaul or auto--and that must be in manual, or it may be a switch that has a spring attached and you must hold the switch to keep the lens stopped down)
02-07-2016, 07:49 PM   #18
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The particular lens I have is a Soligor T-mount so I use a T-mount-to-M42 adapter and then put that into a M42-to-K-mount adapter.

So there is no interaction between the lens and the camera I think.

I shoot full open (f2.8) in Av mode and it is underexposed (too dark).
02-07-2016, 07:50 PM   #19
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The particular lens I have is a Soligor T-mount so I use a T-mount-to-M42 adapter and then put that into a M42-to-K-mount adapter.

So there is no interaction between the lens and the camera I think.

I shoot full open (f2.8) in Av mode and it is underexposed (too dark).

---------- Post added 02-07-16 at 08:24 PM ----------

The thing I am puzzled about is that I gather that the way that the Av mode works in general is that if the camera is in Av mode, it measures the light and it sets the shutter speed according to the amount of light it measures to make a good exposure.

Is that correct?

If that IS correct, then I don't understand why my images are looking underexposed when I use Av mode with a completely "disconnected (electronically)" T-mount/M42 lens? In this case, the only "information" the camera has to go on is the amount of light that it is measuring, so it just needs to figure out how long the exposure time is needed (aka the shutter speed).

02-07-2016, 09:10 PM   #20
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I have a couple lenses that tend to be consistently underexposed using the camera metering (one is a third party "A" lenses and one is a third party "M" lens). I have read other threads that have mentioned this with certain lenses.

Do some exposure bracketing with your lens and find the place where the exposure is right, then do some shooting in other situations and see if it is consistent. Then you will at least know where to start. I find I do a lot of bracketing with my vintage lenses (and even with the newer lenses). Auto bracketing is nearly always turned on on my camera.
02-07-2016, 09:33 PM   #21
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QuoteOriginally posted by Mans Hagberg Quote
. . . On my Pentaxes: Menu, C, item 26 or thereabouts, "Using Aperture Ring" check "Enable". Then the aperture you select on the lens works very well with "Manual" and green button. . . .

I have to do that with my K110D, and also turn the AF/MF switch to Manual Focus. Beyond that it's pretty easy to use my old M42 or K-mount film lenses or later Pentax A lenses, though probably somewhat slower than using lenses that can take advantage of all of the automatic features the K110D could take advantage of.
02-08-2016, 06:34 AM   #22
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QuoteOriginally posted by KC0PET Quote
I have a couple lenses that tend to be consistently underexposed using the camera metering (one is a third party "A" lenses and one is a third party "M" lens). I have read other threads that have mentioned this with certain lenses.

Do some exposure bracketing with your lens and find the place where the exposure is right, then do some shooting in other situations and see if it is consistent. Then you will at least know where to start. I find I do a lot of bracketing with my vintage lenses (and even with the newer lenses). Auto bracketing is nearly always turned on on my camera.
I tried something similar to what you said, but it didn't work consistently even with this one lens (the Soligor T-mount on M42). What I did was set the camera to overexpose (+2), and that worked when I took pics in a couple of places, but I think it was still underexposed in one darker area. I guess I have to stick to using M mode, which works consistently even with full manual lenses.

Thanks,
Jim
07-22-2016, 04:28 AM   #23
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QuoteOriginally posted by ohaya Quote
Hi,

I'm still confused about Av (or Av is not working for me), with full manual (like an M42) lens.

If I put the mode to Av, I thought all I had to do was leave the lens wide open, e.g., with the 28mm Soligor I set it to f2.8, and put the mode to Av. Whether or not I hit the green button, and then shoot, it looks like it's coming in underexposed (too dark).

Can someone explain how I should use Av with such an manual lens?

Thanks,
Jim
Jim,

The way I found the Green Button to work is as follows:

1> Camera ring set to "M"
2> Focus switch set to "M"
3> ISO is NOT set to Auto (it is manually selected)
4> Green button will stop down lens & meter
5> Shutter speed is automatically set by camera on click
6> Bracketing works - in this case the shutter speed changes to get the three shots

The Green button (stop down metering) does not work if ISO is set to a range - the camera then meters and shoots with the lens wide open.

Sunil Gupta

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