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10-09-2012, 12:26 AM   #16
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Hmmm.... Followed this topic to try and help me get to grips with using manual lenses.

I have to say that I am getting very confused about use of M lenses and the K-01. For example I put my Agfa-Color 50 F1.4 lens on my K-01 this morning (it does not have the "A" setting on the lens) and set it to F8.

I set the camera to Av mode and as I point it at different subject areas in my study the Shutter speed varies (much as I would expect - and how both my Samsung GX-10 and NX100 handle manual lenses) and on shooting I get a correctly exposed image.

I then set the camera to M mode and when pointing at the same subject as I used in Av mode, I depress the green button for it to select the shutter speed and again I get a correctly exposed image. However something really does not make sense.

With the first image the Settings were:
Aperture: F8 (set on lens - this is a mechanical adjustment and nothing the camera does can change it)
ISO 800
Shutter Speed: 1/80s

With the 2nd image the settings were:
Aperture: F8 (see above)
ISO 800
Shutter Speed: 0.4s

But both images were correctly exposed. The settings can't both be correct as that just does not make any scientific sense. Aperture and ISO are both fixed, so it must be the Shutter speed that is wrong in one of them. Any ideas about what crazy something is going on here?

Neil

10-09-2012, 01:40 AM   #17
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Update...

I've been doing some further research and found this thread:

https://www.pentaxforums.com/forums/pentax-k-01/179185-k-01-green-button.html

I note that while I can use Av Mode when using a Pentax M lens or equivalent, and exposure seems to be correct - as the OP observed in the initial post on this thread - there are out of focus issues that do not exist when using M Mode. While I observe this myself having done some outdoor shooting today, I can't understand it. I just don't see how either depth of field or focus can be affected by the mode. The focus point is determined by the focal point adjustment on the lens and depth of field is a function of the aperture that has been set. Both of these are manually set by the lens. The only variables that the camera can adjust are Shutter speed and sensitivity (ISO) and I can see no way that these should affect either Focal Point or DOF. So it really is a mystery to me how the K-01 can manage to screw these up when operating in Av mode - especially when it manages to return a correctly exposed image!

So - I know WHAT to do - I just don't understand WHY and that really annoys me.

Neil
10-09-2012, 09:50 AM   #18
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In Av mode on K or M lenses, the K-01 just holds the aperture wide open (it overrides the aperture ring by pushing the lever on the back of the lens), although it will change the shutter (and ISO, if on Auto-ISO) to get a correct exposure. I've verified this by shooting lots of blurry pictures of myself - no matter what is set on the lens, the iris never contracts. For K and M lenses, the only option is Manual mode and the green button. This is pretty much the same behavior as previous models. Shooting wide open will probably give a soft image (especially on old glass) and will affect DoF.

The reason for this is that the lens lacks the 'A' contact points to tell the camera its range of apertures, so the camera can't calculate how far to move the aperture lever. Also, K and M lenses used different linkages from A lenses, so even when tinkerers add the contact points themselves, the lens only exposes correctly for part of the range of apertures.

One (big) difference with the K-01, is that most screw-mount lenses, the ones that don't touch any contacts on the mount, DON'T work like the K and M lenses, and the Green Button DOESN'T work. This appears to be a bug in the firmware. However, if you use Auto-ISO, it looks like the camera meters continously, and selects a workable shutter speed and ISO for whatever light is coming through the lens. I've found this to be so handy that I put some cellophane tape on an M lens to make it work like a screw-mount.

Last edited by THoog; 10-09-2012 at 12:11 PM.
10-09-2012, 01:53 PM   #19
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Thanks #Thoog

Your explanation was very clear and I can now see why things are happening as they are.

Neil

10-14-2012, 11:02 AM   #20
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QuoteOriginally posted by THoog Quote
I put some cellophane tape on an M lens to make it work like a screw-mount
This sounds like an excellent "feature" as I would rather use the Green Button for something else. Would it be possible for you to explain how to do this please - where exactly do you put the tape?

Thanks

Tony
10-14-2012, 11:53 AM   #21
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QuoteOriginally posted by TonyM Quote
This sounds like an excellent "feature" as I would rather use the Green Button for something else. Would it be possible for you to explain how to do this please - where exactly do you put the tape?
Sure thing! A picture is worth a thousand words, so here's a picture. And some words.

Making an M lens automatic, sort of. | Flickr - Photo Sharing!

Last edited by THoog; 10-14-2012 at 11:59 AM.
10-14-2012, 12:50 PM   #22
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Excellent! Thank's very much. (This also made me revisit a cheap Vivitar 2x converter that I had assumed was defective because the green button didn't work. Et viola, same issue! The plastic mount made it behave in the same way, constantly metering.)

Regards

Tony

PS Another interesting side-effect is that focus peaking covers the dof for the selected aperture, not wide open!

Last edited by TonyM; 10-14-2012 at 01:19 PM. Reason: Extra information
10-14-2012, 04:13 PM   #23
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Yeah, the non-conducting mount issue comes up from time to time (usually for a camera not being able to do catch-in-focus with an old lens). Fixes included inserting a piece of aluminum foil under the mount, conductive paint, etc. Thanks to Auto-ISO, there's finally an up-side. I hadn't thought about the DoF, but you're right (must resist the urge to spend an hour making the DoF slither across the carpet...) (okay, so I have a Low Threshold of Entertainment.)

10-15-2012, 08:29 PM   #24
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With the new firmware update, the green button now works with screw-mount lenses. In M mode you can now set the aperture on the lens and press the green button to set the correct corresponding shutter speed. The +/- EV scale still appears in the viewfinder, and you can use the wheel to adjust your shutter speed.
10-17-2012, 08:35 AM   #25
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With new FW still have blurry images with pentax-A ?
10-17-2012, 11:58 AM   #26
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QuoteOriginally posted by towa Quote
With new FW still have blurry images with pentax-A ?
If you try to use Av mode with a K- or M- series lens (that is soft wide open), yes. Av mode holds K- and M-series lenses wide open, regardless of the aperture ring setting. This is the same for all Pentax dSLRs, not just the K-01.

The only thing the firmware changed with respect to manual lenses was that in Manual mode, the green button now works with M42 screwmount lenses, or lenses with a non-conductive plastic or painted mount that the camera can't detect.
09-03-2013, 12:43 PM   #27
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I'm confused

QuoteOriginally posted by romansolar Quote
thanks guys!

today i used for a first time my "new" revueonon 1.4 50mm. I did some shooting, wonderful images, but it somehow not so sharp as i thought could have. Well, when i switched to manual on my Kr and found finally for what i have AV button, everything seems just fine! tomorrow i will do some outdoor shooting, but i am sure i will be pleased

thanks again
I shoot with A lenses...are we saying that they do not stop down to the correct arperture using Av on the K 01?
09-03-2013, 01:27 PM   #28
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QuoteOriginally posted by Thespoiler Quote
I shoot with A lenses...are we saying that they do not stop down to the correct arperture using Av on the K 01?
A lenses (using the A setting on the aperture ring) do stop down to your selected aperture when taking a shot in Av mode. The K and M lenses do not stop down in Av mode, and so you must use M mode and the green button to get correct exposure.
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