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03-31-2011, 08:53 AM   #1
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Dark photos with K-x and manual lens

I bought myself a nice cheap manual lens on Ebay to go with my K-x to teach myself how to use them, but I'm having some problems. This is the lens:

PENTAX PK Cosina MC Z 80-200mm 4.5 on eBay (end time 22-Mar-11 22:47:55 GMT)

I found the aperture setting so that I can actually take photos but they all seem to come out quite dark. When I turn the camera on I'm asked for the focal length, and it seems like the smaller the number I use, the lighter the picture is, but even setting it to 8 produces dark photos.

I've followed the instructions in the manual lenses sticky, but the photos still seem dark. Where am I going wrong?

Thanks for any help

P.S. Please be gentle, I know next to nothing!

03-31-2011, 09:20 AM - 1 Like   #2
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From what I've read, every manual lens needs some kind of exposure compensation, you just have to find how much is necessary for yours and then stick with that value.
03-31-2011, 09:31 AM   #3
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Fair enough, sounds like an easy fix

Thanks
03-31-2011, 09:34 AM   #4
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Can you post samples with exif?

I'm not familiar with this lens, and I can't quite tell by the picutre, but I'm assuming it operates like a Pentax M and doesn't have an "A" setting. What this means is that while the lens is mounted on the camera, the aperture blades don't move when you rotate the aperture ring. As a result, you need to use it in manual mode on the dial and "green button" meter for exposure.

03-31-2011, 09:34 AM   #5
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Your welcome.
03-31-2011, 09:45 AM   #6
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QuoteOriginally posted by Tippon Quote
I bought myself a nice cheap manual lens on Ebay to go with my K-x to teach myself how to use them, but I'm having some problems. This is the lens:

PENTAX PK Cosina MC Z 80-200mm 4.5 on eBay (end time 22-Mar-11 22:47:55 GMT)

I found the aperture setting so that I can actually take photos but they all seem to come out quite dark. When I turn the camera on I'm asked for the focal length, and it seems like the smaller the number I use, the lighter the picture is, but even setting it to 8 produces dark photos.

I've followed the instructions in the manual lenses sticky, but the photos still seem dark. Where am I going wrong?

Thanks for any help

P.S. Please be gentle, I know next to nothing!
Oops, forgot to mention this part.

The focal length setting won't effect the exposure. That setting is for shake reduction.
03-31-2011, 10:07 AM   #7
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I have a very similar manual lens, and it really depends on the lighting for how much light you get in the camera. In general, though, I have found that pushing the white balance up about +1 while in Av aperture priority mode compensates for it pretty well.

Also, I have read that if you're using a manual zoom, setting the focal length to the midpoint between the two ends will work well enough for the shake reduction. On my 80-200mm, 135 seems to work well.
03-31-2011, 10:15 AM - 1 Like   #8
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QuoteOriginally posted by icywindow Quote
I have a very similar manual lens, and it really depends on the lighting for how much light you get in the camera. In general, though, I have found that pushing the white balance up about +1 while in Av aperture priority mode compensates for it pretty well.

Also, I have read that if you're using a manual zoom, setting the focal length to the midpoint between the two ends will work well enough for the shake reduction. On my 80-200mm, 135 seems to work well.
I think instead of "white balance" you meant "exposure compensation".

However, I don't think this lens will meter properly in Av mode. The lens appears to lack an "A" setting and, therefore, requires the user to use manual mode and green button metering.

03-31-2011, 11:45 AM   #9
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This may be your problem indeed, I think you keep it in AV, so your camera meters wide open, and closes the aperture when taking the picture, resulting in darker photos than expected. That is because these newer cameras have what's called a "crippled" mount, which means they lack a lever which was able to tell what aperture you're at. It became redundant when the A series lenses came out. Now what the green button does, is briefly closes the aperture, takes a reading of the light that will actually fall on the sensor, keep that reading in memory and expose for that. It's called stop-down metering, and it's as antique as the Spotmatics, before open-aperture metering came out. You'll notice that you won't have to hit the green button before every picture, as long as you don't change exposure settings in the camera and the lighting conditions don't change.
There is another option in the menu that should be modified, I think, which sets what the green button does in M mode. It should be "Tv shift" I think, it must vary the shutter speed according to the current aperture.
I hope that's it. If this is the case, then what I've told you before, about exposure compensation, is just for fine-tuning. Good luck.

Last edited by kcobain1992; 04-03-2011 at 02:55 PM.
03-31-2011, 03:14 PM   #10
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Thanks guys

I set the camera to M on the dial and MF, and tried both of the green button settings, but still got dark photos. I could change the ISO setting, but couldn't see where to change the exposure compensation. I've attached a pic taken with the manual lens and one taken with the kit 18-55 lens for comparison, both with ISO set at 1600.

It's quite late now, so I'm going to get some sleep and come back with a fresh head tomorrow

Thanks for helping me with this
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03-31-2011, 04:29 PM - 1 Like   #11
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Exposure compensation is accessed by pressing the black +/- button to the left of the green button on the K-x, then using the zoom wheel to jog left or right to set the exposure comp.

Also, it was not clear to me whether you had reprogrammed the green button to use Tv Shift, so here's the instructions in case you hadn't.
(copy/pasted from Using Older Lenses with the PENTAX K-x | Pentax Support)

To set up your PENTAX K-x to use older PENTAX lenses:
Press the Menu button
Press the left button on the four-way controller to get to page 4 of the Rec. Mode menu
Press the down button on the four-way controller, select Green Button
and press the right button on the four-way controller.
Press the down button on the four-way controller, select Action in M Mode
then press the right button on the four-way controller and select Tv SHIFT. Press the OK button then the Menu button twice.

Last edited by icywindow; 03-31-2011 at 04:31 PM. Reason: Directionally challenged.
03-31-2011, 05:44 PM - 1 Like   #12
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QuoteOriginally posted by Tippon Quote
Thanks guys

I set the camera to M on the dial and MF, and tried both of the green button settings, but still got dark photos. I could change the ISO setting, but couldn't see where to change the exposure compensation. I've attached a pic taken with the manual lens and one taken with the kit 18-55 lens for comparison, both with ISO set at 1600.

It's quite late now, so I'm going to get some sleep and come back with a fresh head tomorrow

Thanks for helping me with this
What was your aperture on the manual lens shot?

Forgive me, but I don't have a Kx and I'm not sure what the bolded section means. What two settings does the green button have?

Reading icywindow's link shows the green button can be customized to meter when pressed. Interesting since it also says the exposure compensation (+/-) button will do the same thing. So, you have two buttons to do the same task.

To get your exposure you just need to be in Manual mode, turn the aperture ring to your desired setting, press your customized green button or the exposure compensation button, then take your picture.

You have at least three variables comparing these images:
  1. You changed lenses
  2. The first one has more of the largely white object in the center. The second one has a much wider view. If the scene changes, even a single lens could give a different exposure.
  3. The manual lens is metering center weighted. The kit lens is using multi-segment. So, not only did you change the scene, but the camera changed the metering mode that made it more likely the exposures would be even more different. Even if you didn't change the lens, this difference in metering mode could change the exposure.

    Metering For The Right Exposure

And lastly, exposure compensation does not work in manual mode. You simply change the values of your exposure; ie change the aperture or the shutter speed.

[edit]I just wanted to add something about the different metering modes.

With your kit lens the camera can use any of the three modes. With a manual lens the camera can only use spot or center weighted. You could, to get a better comparison of exposures, set the camera to spot or center weighted, take a picture at 80mm on the Cosina, and then put the kit lens on, recompose for the same composition and take a second picture. Oh, and set the F Stop to the same value on both lenses. This way the only number that may vary is the shutter speed.

Last edited by wasser; 03-31-2011 at 06:00 PM. Reason: added bottom edit
04-01-2011, 10:35 AM   #13
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QuoteOriginally posted by wasser Quote
And lastly, exposure compensation does not work in manual mode.
Sorry about that, really didn't realize until now.
04-01-2011, 10:43 AM   #14
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QuoteOriginally posted by kcobain1992 Quote
Sorry about that, really didn't realize until now.
Metering in manual mode should be really accurate even with a manual lens, at any aperture. The trick is to make sure you meter off the the right part of the scene. For instance, if you're using center-weighted metering, and hit the green button when you're centered on a bright sky, it will underexpose the whole image because it's trying to make the sky gray. You really have to find the area that you want to be the mid tone and meter off that before settling on a final composition.
04-03-2011, 01:39 PM   #15
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Sorry about the slow reply. Thanks for all the responses and advice

I think I've cracked it! When using the kit lens, the +/- button acts slightly differently to with a manual lens, so I was getting myself confused. With the kit lens, it lets you change what looks like a sliding scale at the bottom left of the display that goes from +3 to -3, while with a manual lens it lets you change a value at the top left of the display which goes from 1/6000 to measurements like 0.3". Apparently it's the shutter speed, which would explain why I've been under / over exposing pictures.

I managed to take a half decent pic of some lambs, which isn't great, but is much better than I was doing

Thanks again for all the advice
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