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03-28-2012, 01:36 PM   #1
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Using M lens

I will put camera on Manual, select an aperture, press the +/- button for the camera to select a shutter speed. I see the speed on the screen and I know from experience that is too fast or slow(I get too fast a speed most times) and if I press it again a few times I get a different shutter speed. I don't understand why that's happening. I have a K-x. Comments much appreciated.
Here is what happened just now:
Using a Viv 75-205 at f8, took a pic at 1/125. Pressed button mentioned above and speed jumped to 1/400 then to 1/320, then to 1/250. Took a pic at 1/320(a little darker obviously)

03-28-2012, 02:24 PM   #2
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Pressing the +/- key takes a light meter reading based on exactly where the camera is pointed when you press it. So depending on which metering method is selected if you are looking at a scene with sharp differences in brightness you could easily get different readings. Check that you are not using spot metering as well, because that would make it even worse in this case.
03-28-2012, 02:55 PM   #3
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Thanks jatrax, I aim at the same subject and note these changes all within 10th to 20th(guessing) of a second. Spot and center-weighted metering is the only metering available in manual on K-x. Don't know about other bodies. I will try center-weighted next chance I get.
03-28-2012, 03:23 PM   #4
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Hi Royden,
And you can select bracket mode in M to get 3 exposures by shutter speed (-, 0, +) where you select the steps.

03-28-2012, 03:30 PM - 1 Like   #5
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QuoteOriginally posted by royden Quote
Thanks jatrax, I aim at the same subject and note these changes all within 10th to 20th(guessing) of a second. Spot and center-weighted metering is the only metering available in manual on K-x. Don't know about other bodies. I will try center-weighted next chance I get.
I think you'll have less shutter speed fluctuations by using center-weighted metering. I'd def. give that a try.
03-28-2012, 04:50 PM   #6
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QuoteOriginally posted by royden Quote
I will put camera on Manual, select an aperture, press the +/- button for the camera to select a shutter speed. I see the speed on the screen and I know from experience that is too fast or slow(I get too fast a speed most times) and if I press it again a few times I get a different shutter speed. I don't understand why that's happening. I have a K-x. Comments much appreciated.
Here is what happened just now:
Using a Viv 75-205 at f8, took a pic at 1/125. Pressed button mentioned above and speed jumped to 1/400 then to 1/320, then to 1/250. Took a pic at 1/320(a little darker obviously)
If you're pretty sure you are aiming at the same spot when you get these very different shutter speeds at f8, then I would check the aperture blades to make sure they are "snappy". Sluggish blades will give you some odd/different readings. The easiest way to check is to use the lens wide open at f3.8 and take several readings with the green button. You can also take a look at the lens off the camera, set at f8 and actuate the little lever, it should be pretty quick to close AND open...

I've found the K-x is pretty accurate when using the green button...
03-28-2012, 05:02 PM   #7
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QuoteOriginally posted by royden Quote
Spot and center-weighted metering is the only metering available in manual on K-x. Don't know about other bodies. I will try center-weighted next chance I get.
I believe that is correct. If you are using spot metering I suspect that is your problem, spot metering uses a very small sample. I don't have the manual handy but I think maybe 3 degrees?? Just the act of pushing the button might move the camera enough to get different readings. Try center weighted and see if that changes things. If not, post back, maybe somebody else has another idea.

I have found green button (or +/-) metering to be quite accurate with manual lenses so you should not be seeing that kind of change unless something is wrong.
04-01-2012, 10:53 PM   #8
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This takes getting used to. Everytime you move a bit you have to meter again by pressing the green button. Several times I have recomposed and taken a shot only to realise the exposure is wrong because I forgot to press the green button to meter again.

In Av mode you dont need to do this at all as the shutter speed keeps changing as you recompose. The only problem is that your lens is stuck wide open.

04-02-2012, 04:05 AM   #9
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QuoteOriginally posted by Culture Quote
This takes getting used to. Everytime you move a bit you have to meter again by pressing the green button. Several times I have recomposed and taken a shot only to realise the exposure is wrong because I forgot to press the green button to meter again.

In Av mode you dont need to do this at all as the shutter speed keeps changing as you recompose. The only problem is that your lens is stuck wide open.
Actually what you should do with spot metering is point it at what ever you want in the middle of the histogram. The meter will attempt to make what it sees the center of the histogram then the rest of the frame should be fine. I generally meter off something that is mid grey. Either a tree trunk or roadway
04-02-2012, 07:49 AM   #10
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In M(anual metering) mode, it is NOT necessary to hit the Green button for every exposure. Such re-metering is only needed when the light changes. I'll often meter, shoot, chimp, adjust to my satisfaction, then leave the shutter-aperture-ISO alone for some time, as long as ambient light remains the same.

I'll trot-out this example again: One spring afternoon I was in the red-rock country near Sedona Arizona. (Will be again in a couple weeks too.) Blue skies, puffy white clouds, red rocks, tawny sand, dark-blue mountains, vegetation from dark to light green, multi-colored structures, and me with my K20D and DA18-250.

For a set of 'scapes, I proceeded as described above -- meter, shoot, chimp, adjust, lock-in -- kept the same exposure until the sun was closer to the horizon. If I'd been in an Auto mode or had re-metered constantly, the intensity of sky+clouds+hills etc would be different in every shot. That's not what I wanted. I wanted, and got, consistent exposures, a nice set of photos that work together as a set.

This is one reason to keep a neutral-gray card handy. Meter the ambient light, not a specific subject. This is basically how the Sunny-16 Rule works -- shooting the light. And it's how I've shot subjects in tricky light with just a center-weighted film P&S: Look for something that's about the same shade as the subject, and read off that. I've used my hand, or sleeve, or nearby ground, etc.

Shooting without aperture automation ain't no big thang. Just practice a bit.
04-02-2012, 08:15 AM   #11
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Right, changing exposure for every shot is just plain crazy talk. The differences between dark and light objects with a scene is tiny compared to the differences in light levels between scenes. Metering is mostly to account for the latter, not the former. At most, occasional one-click-of-the-thumb-wheel adjustments if you see that you are focusing on an unusually dark or unusually light object within the scene might be necessary.
04-02-2012, 03:40 PM   #12
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I do the same. Get it set for a good exposure then leave it alone until I know the light has changed. So far it has worked great. I found this out while learning with Pentax KX and K1000 film cameras. No need to reset the exposure every time, except on cloudy days when lighting changes every few seconds. In fairly constant lighting conditions I rarely have to change anything unless I change the aperture deliberately for depth of field or change shutter speeds to stop motion. When shooting for a long time I check it occasionally, but most of the time it rarely changes. For example yesterday I started shooting macro shots outside, f8 at 1/750 was working fine. Kept it there most of the day, switched between two 50mm lenses and the Vivitar 200mm M42, just made sure I started at f8 and 1/750 every time and never had to change it.
04-02-2012, 09:50 PM   #13
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Thanks for all the answers and I appreciate this very much. Because it is bug for me to press the green button all the time thinking that I am metering wrong.

So let me get this straight. You meter ambient light but not the object that you are shooting. This makes sense to me if you are shooting landscape like RioRico explained.

But if you have an af lens then isnt it always metering when you recompose and focus? At least that is why i thought i always had to press the green button. Or do you mostly lock the exposure?

I guess I have to get me a grey card.
04-03-2012, 04:00 AM   #14
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QuoteOriginally posted by Culture Quote
Thanks for all the answers and I appreciate this very much. Because it is bug for me to press the green button all the time thinking that I am metering wrong.

So let me get this straight. You meter ambient light but not the object that you are shooting. This makes sense to me if you are shooting landscape like RioRico explained.

But if you have an af lens then isnt it always metering when you recompose and focus? At least that is why i thought i always had to press the green button. Or do you mostly lock the exposure?

I guess I have to get me a grey card.
If you have an AF lens, the camera is always metering , yes, but in manual mode, it is not adjusting, only telling you the over/under exposure for your present settings, so using any A lens in manual mode allows you to meter on what you want by pressing the green button and it then tells you the over/under for the subject /scene as a whole against what your settings will give
04-03-2012, 06:49 AM   #15
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QuoteOriginally posted by Lowell Goudge Quote
If you have an AF lens, the camera is always metering , yes, but in manual mode, it is not adjusting, only telling you the over/under exposure for your present settings, so using any A lens in manual mode allows you to meter on what you want by pressing the green button and it then tells you the over/under for the subject /scene as a whole against what your settings will give
Quite right. If you use an AF or A-type lens, have tricky lighting, and want a subject to be exposed neutrally, then set the camera to M mode and spot metering. Read|meter the subject carefully. Take a test shot, chimp it, adjust exposure as needed, and fire for effect, as we say in the field artillery biz. If the lighting isn't so tricky, then set metering to center-weighted or matrix and proceed as above. In manual mode, once you meter for the right exposure, you can just leave aperture+shutter+ISO alone until the light changes.
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