K10D - AV vs Manual discrepancy?

<p>Just something weird I noticed the other day while messing around, and not sure if this is normal. For some reason, AV mode seems to give much brighter images than in manual. Both these were shot at same aperture, and ISO100.</p>

<p>AV mode, ISO100, 1.5 second exposure</p>

 

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<p>But in manual mode I get a much darker image, even with a much longer exposure (4 seconds).</p>

<p>Manual mode, ISO100, 4 second exposure</p>

 

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<p>And the exposure compensation was set to 0 while in AV mode, by the way. I notice this even more so when using a flash. Certain situations, even shooting at f22 with the flash dialed down the image will be blown out using AV mode. Is my camera just borked, or does AV mode work differently than I think it does?</p>

<p>Or could it be something to do with my lens? As this only seems to happen with my manual lens, but not the kit lens. Maybe the contacts need to be cleaned? Some other part of the lens causing it? Thanks.</p>

<p>Which 'manual' lens? Using 'A' on the aperture ring? Using stop-down metering?</p>

<p>And what kind of flash/ flash exposure--P-TTL? Auto flash? Manual?</p>

<p> </p>

<p>The manual lenses have different types of coupling which result in different levels of compatibility to your K10D. That's why to give you a correct answer we need to know more specifically about your "manual" lens and exactly HOW you used that lens in Av and Manual modes because it's also likely that you used it in a wrong way</p>

<p>Well these are from my Soligor 80-200mm. It's an older lens, at least before '87 or so which is when I came in possession of it. Neither of these are using a flash, and I've deleted all the ones that were blown out, but will try to reproduce it later, if need be. Also happens with my Focal 135mm, too. And there is no "A" on the aperture ring (on either lens), so I have it set to "permitted" in the menu to allow operation in modes other than "A". And aside from that all other menu options are still at default, as I've never messed with any of them.</p>

<p>ok, so what did you do in mode A? did you: turn mode dial to Av, turn the back wheel to set aperture=F8? and Press shutter release fully down?</p>

<p>and what did you do in mode M? ...</p>

<p>John, Without an "A" contact he wouldn't be able to set an f-stop on the back wheel. The LCD would only show "--" instead of an f number.</p>

<p>On my preset lens, I can shoot in Aperture Priority to have it adjust the shutter for me; it's the best part about the M42 lens functionality. In Manual Mode with the same lens, I just ensure that the shutter is what I need. 1/1000 @ f/2.8 is still 1/1000 @ f/2.8, but there is one variable we haven't talked about yet...</p>

<p>Brendon, do you have Auto ISO turned on? In Manual mode, the ISO setting wouldn't change, but in some other Automatic mode, the camera might decide you need more ISO. I don't have a K10 yet, but I know I set my ISO and leave it off Automatic. This could be the factor we're forgetting about.</p>

<p>If you are using the aperture ring, not the A position, with a K mount lens, the camera will only shoot wide open in Av mode. I think that may be the source of your issue?</p>

<p>Brendon, what aperture did you use in each case? When you shot in Av you shot wide open (I can assure you that), but what about in M mode? What did you set the aperture to?</p>

<p>ISO was not on auto, manually set to 100. Aperture I'm pretty sure was wide open (4.5), for both images. I had initially taken the first, brighter shot in AV mode, so figured a longer exposure in manual would make the sprinkler show up even better. I certainly wouldn't rule out user error, but I really don't think I would have stopped it down for the manual shot considering I wanted it to be even brighter.</p>

<p>I'll keep running some tests, but it seems to be an intermittent thing, or at least it has been with using the flash. I think sometimes it just adds its own exposure compensation, regardless of settings. Just did a couple of shots in daylight, setting it on AV first which metered at 1/30. So set it to manual at 1/30 and they seemed identical. Probably drive myself crazy trying to reproduce it to no avail. Going to give the lenses a good cleaning, too. I've only ever cleaned the glass up until now. Time to give the base rings a good rub down, methinks.</p>

<p>I would sort out what is going wrong with non-flash exposures before adding the complication of the flash unit. I think that Nick is probably on the right track - the Av mode on a K10D (or any other camera probably) is not designed for use with a fully manual lens. The non-manual modes in a dSLR (P, Av, Tv, Sv) rely on the camera being able to set the aperture on the lens. I don't know the Soligor 80-200, but if it is like my '80s era and earlier fully manual lenses (i.e. without an A (for 'auto-aperture') setting on the aperture ring) then it cannot send or receive information from the camera, and the camera has no idea what aperture the lens is set to. Kind of defeats the purpose of Aperture Priority mode, as well as confusing the camera. I would be surprised if there were any electrical contacts between your Soligor and the camera for you to clean.</p>

<p>I do not use fully manual lenses on anything but M mode on my K10D, but that works well for me. Av mode does not, and I don't expect it to. (The manual says somewhere that you will get exposure errors with manual lenses on Av)</p>

<p>Brendon, have you used the green button to set the exposure in M mode? If not, try this:<br>

In M mode, set the lens to the aperture you want, then press the green button. The camera will stop the lens down to the set aperture, measure the light and set a shutter speed. You can then take the shot, or vary the speed. Nine times out of ten, the camera suggested speed is spot on for me. </p>

<p>None of the above explains why you got the exposures you did. But I would make sure that your manual lenses are working properly with the camera in M mode. If they are then you can rule out lens and camera errors. If not, let us know what results you do get.</p>

<p>You're right in there are no contacts on the lens itself, but thought maybe some gunk on the base ring might cause some error between the contacts on the camera.</p>

<p>Sounds about right, tho. 90% of the time AV mode works fine, with the occasional slight over-exposure. This one was just drastic enough for me to try to suss it out. Guess I have to go with "it's a feature, not a bug". Thanks everyone.</p>

<p>brendon,<br>

in case you have not read this article, check this out<br>

http://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-manual-lenses-m42-screwmount-m-k-pentax-dslrs-f.html#post1140022<br>

--osamu</p>

<p>The other question is about the flash--I believe that the built-in flash will always fire full power with a lens like this.</p>