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01-23-2016, 02:12 PM   #1
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K-30 metering with green button

I've recently begun testing some of my manual lenses at the full spectrum of f-stops. Basically, I set the camera with lens on a tripod, focus on an object and take a picture. I reset the apature one stop, press the green button and take another picture.

As I review the rsults, I find a significant difference in exposure while I thought they would be much closer. What am I missing.

The following pictures display the extreme difference.

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01-23-2016, 02:21 PM   #2
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The second photo was in spot metering mode, and you pointed the camera at a darker part of the image, which resulted in foreground overexposure. The first photo was center-weighted, so the deer probably covered most of the metering area and thus resulted in a darker image.

I would stick with matrix metering for the most part.

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01-23-2016, 02:25 PM   #3
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QuoteOriginally posted by Adam Quote
The second photo was in spot metering mode, and you pointed the camera at a darker part of the image, which resulted in foreground overexposure. The first photo was center-weighted, so the deer probably covered most of the metering area and thus resulted in a darker image.

I would stick with matrix metering for the most part.
Yes, I noticed that after posting. Here are two better examples.
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01-23-2016, 02:26 PM   #4
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One metering mode is center weight, the other is spot. Can make a huge difference, as evidenced in your shots.

Edit: looks like we were trying to help all at once! Well, now you've got it.

---------- Post added 01-23-16 at 01:30 PM ----------

QuoteOriginally posted by onlineflyer Quote
Yes, I noticed that after posting. Here are two better examples.
Not sure why, but can't read these EXIFs.

---------- Post added 01-23-16 at 01:44 PM ----------

Now I can read them, but your f stop isn't showing. If you're saying that the two shots above are only one f stop apart, yet the slower shutter speed is darker, something's up with your aperture. Lens? Camera? What happens when you put on a AF lens?

01-23-2016, 02:50 PM   #5
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QuoteOriginally posted by Kath Quote
One metering mode is center weight, the other is spot. Can make a huge difference, as evidenced in your shots.

Edit: looks like we were trying to help all at once! Well, now you've got it.

---------- Post added 01-23-16 at 01:30 PM ----------



Not sure why, but can't read these EXIFs.

---------- Post added 01-23-16 at 01:44 PM ----------

Now I can read them, but your f stop isn't showing. If you're saying that the two shots above are only one f stop apart, yet the slower shutter speed is darker, something's up with your aperture. Lens? Camera? What happens when you put on a AF lens?
F-stop at different ends of the spectrum, nearly wide open and nearly close
01-23-2016, 03:09 PM   #6
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Here are two more, lens is a M 50mm f1.7. Apature setting f1.7 and f22
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01-23-2016, 05:09 PM   #7
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Sorry, @onlineflyer, it sounds to me like this is a function specifically of manual lens behavior on your K30. I use AF lenses exclusively, so I can't be helpful.

I wonder if you might get some useful responses from the folks that hang out here: https://www.pentaxforums.com/forums/122-lens-clubs/27739-m-club-364.html
01-23-2016, 05:21 PM   #8
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QuoteOriginally posted by Kath Quote
Sorry, @onlineflyer, it sounds to me like this is a function specifically of manual lens behavior on your K30. I use AF lenses exclusively, so I can't be helpful.

I wonder if you might get some useful responses from the folks that hang out here: https://www.pentaxforums.com/forums/122-lens-clubs/27739-m-club-364.html
Thanks, I'll give this thread some time but if i don't get any clear answers I may take up your suggestion.

01-24-2016, 02:38 AM - 1 Like   #9
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I come across this all the time with older lens. I am pretty sure the iris is a little sticky and not responding at a consistent speed. So when when you press the green button it is not metering correctly and when you shoot it responds differently. Try (with a M lens) by not quite clicking it home (unmounted by 7-8 mm) and set the camera to AV and see if you get a correct exposure. This trick means the body can not reach the aperture lever of the lens so the lens works manually just like an old M42 does. I think a lot of M irises are sluggish so this is how I use them.
Another issue that threw me a lot (until I worked it out) is that you tend to hold the camera away a little to find the green button and with your eye off the viewfinder light can pour in there stuffing the exposure reading. I think it is ridiculously poor design that light can enter that way and stuff up basic metering.
01-24-2016, 03:49 AM   #10
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QuoteOriginally posted by GUB Quote
Another issue that threw me a lot (until I worked it out) is that you tend to hold the camera away a little to find the green button and with your eye off the viewfinder light can pour in there stuffing the exposure reading. I think it is ridiculously poor design that light can enter that way and stuff up basic metering.
This is something every (D)SLR suffered from since the started using built in TTL light meters some 50 years ago. It's hard to avoid as the light meter is up in the prism housing.

It's the reason why there often comes a cover to block the OVF with the camera.
PENTAX ME Viewfinder Cap reviews - Pentax Camera Accessory Review Database
01-24-2016, 12:49 PM   #11
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QuoteOriginally posted by Fogel70 Quote
This is something every (D)SLR suffered from since the started using built in TTL light meters some 50 years ago. It's hard to avoid as the light meter is up in the prism housing.

It's the reason why there often comes a cover to block the OVF with the camera.
PENTAX ME Viewfinder Cap reviews - Pentax Camera Accessory Review Database
Yes I realize that, and the system works well until you progress to using a tripod or using the green button. The funny thing is it is a not very publicized issue, leaving a lot of people confused. It could be designed out with auto darkening glass and its own little light meter. That would be a far more important performance based gizmo than some of the metering modes.
01-24-2016, 01:50 PM   #12
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QuoteOriginally posted by GUB Quote
Yes I realize that, and the system works well until you progress to using a tripod or using the green button. The funny thing is it is a not very publicized issue, leaving a lot of people confused. It could be designed out with auto darkening glass and its own little light meter. That would be a far more important performance based gizmo than some of the metering modes.
Thanks everyone for your input.



---------- Post added 01-24-16 at 04:17 PM ----------

[/COLOR]
QuoteOriginally posted by Adam Quote
The second photo was in spot metering mode, and you pointed the camera at a darker part of the image, which resulted in foreground overexposure. The first photo was center-weighted, so the deer probably covered most of the metering area and thus resulted in a darker image.

I would stick with matrix metering for the most part.
Adam, from what I understand matrix metering is not available with K or M manual lenses.

Per the K-30 e-book:

"When using lenses other than DA, DA*, D FA, FA J, FA, F or A, the metering defaults to Center Weighted."

Am I missing something?

Last edited by onlineflyer; 01-24-2016 at 05:19 PM.
01-25-2016, 08:45 AM   #13
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Okay, the problem has been solved thanks to GUB.

After getting the same results after testing a number of manual, A and FA lenses, I began shooting in live view and started getting proper exposure. I then shot more pics in OVF mode but I placed my thumb over the eye piece to shut out all light before pressing the green button. I could see the shutter speed setting change as I changed aperture and every picture was properly exposed. So, backlight through the OVF was causing the improper exposure setting.
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