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10-13-2010, 09:04 PM   #31
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Commit this chart to memory:

Sunny 16 rule - Wikipedia, the free encyclopedia

In time, it will be all the meter you really need. Also, turn on flashing highlights/shadows in your camera's menu. When a highlight is totally white with no detail, it will flash on the instant preview. Likewise with a shadow totally black.

10-13-2010, 09:41 PM   #32
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QuoteOriginally posted by Obs Quote
After a couple of night shots with the k-x, I have come to the conclusion that metering using stop down via the +/- button is useless. I guess I just save my money for a good DA lens. Can anyone recommend a thread
I am also a newbie in digital photography. I just bought 2 lenses to cover all my need for now: DA 15 and D FA 100 WR. I take mostly landscape, portrait and macro. These 2 lenses produce superb IQ. You can go to the lens forum and look for
(1) DA15 controls my mind; (2) LBA D FA 100mm F2.8 WR.
10-14-2010, 12:44 AM   #33
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One cause for erratic exposures can be malfunction of the lens. Did you try only one lens? Have you checked that the aperture blades move freely and instantenously (at every f-stop)? Also a bent or stiff aperture lever can cause problems.
10-14-2010, 08:37 AM   #34
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QuoteOriginally posted by ovim Quote
One cause for erratic exposures can be malfunction of the lens. Did you try only one lens? Have you checked that the aperture blades move freely and instantenously (at every f-stop)? Also a bent or stiff aperture lever can cause problems.
Another cause for uneven exposures based on the selected aperture is the bright focusing screen added starting with the K10d. Please note that these exposures are easily predicted, as found by Lowell Gouge with his detailed testing, not erratic, but not the same when the aperture changes. With lenses that do not feature the A setting on the aperture ring, the exposure varies based on the aperture. One or two are close enough, go one way and overexposure results and the other side is underexposure.

This effect was resolved on my K10d by replacing the focusing screen with the LL-60 screen from the *ist D series. Lowell did extensive testing on this and reported to the forum nearly three years ago. Each lens tested had an accurate metering aperture, and things went off the rails either side. In the early days of detecting this particular problem there were a number of speculations on this, including a possible cause based on how the aperture stop down lever was regulated. For my own use I tested my trusty M 400/5.6 using the "Sunny 16" meter and assorted combinations of shutter speed and aperture and found that the problem was not mechanical. There is a series on my Flickr pages. I then, following Lowell's advice, purchased and installed the LL-60 screen, and now my metering is even across all aperture values.

10-14-2010, 09:30 AM   #35
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Lowell and Rockie's solution (*ist focus screen) is appropriate for the K10D and K20D. It should not be needed for your K-x. The K-x should meter properly with all non-A contact lenses in M-mode using stop-down metering. This is not true in Av mode. The exposure issues present in the earlier K series bodies were corrected by Pentax for the K-7 and K-x models. If your stop-down settings are completely off the wall, there is either an issue with your camera or with your lens.


Steve
10-14-2010, 09:49 AM   #36
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QuoteOriginally posted by stevebrot Quote
Lowell and Rockie's solution (*ist focus screen) is appropriate for the K10D and K20D. It should not be needed for your K-x. The K-x should meter properly with all non-A contact lenses in M-mode using stop-down metering. This is not true in Av mode. The exposure issues present in the earlier K series bodies were corrected by Pentax for the K-7 and K-x models. If your stop-down settings are completely off the wall, there is either an issue with your camera or with your lens.


Steve
Steve, stopped down metering issue is only partially corrected on the K7 with the biggest improvement in the large aperture area.

It is a very worthwhile exercise for people to validate the exposure behavior of their kit WITH ALL LENSES, as even new lenses like my Tamron XR Di 28-57 F2.8 have exposure errors. It drifts up slightly leading to a 1 stop error by F32.
10-14-2010, 08:12 PM   #37
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I have no experience in disassembling a lens and would like to know how to remove the aperture control lever. If it is too much trouble to remove it, I would use a jewel saw to cut it. Without that lever, there is no more "stop-down" problem. I can open the aperture to focus, then set the aperture and shoot. It is easier for the camera body also without having to hold that lever under tension all the time.
10-15-2010, 11:09 AM   #38
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QuoteOriginally posted by violini Quote
I have no experience in disassembling a lens and would like to know how to remove the aperture control lever. If it is too much trouble to remove it, I would use a jewel saw to cut it. Without that lever, there is no more "stop-down" problem. I can open the aperture to focus, then set the aperture and shoot. It is easier for the camera body also without having to hold that lever under tension all the time.
I think you miss the point a little.

with pentax cameras, depending on model, you either press the green button or the AE button to set the exposure with manual aperture lenses in Manual mode.

exposure normally does not change significantly between shots, therefore untill lighting changes there is no need to do it again. In manual mode the aperture is stopped down to the setting on the aperture ring when you press the shutter button, so you get wide open focusing and exposure control, having already set the expsoude with the pressing of the green button.

In stop down mode, the metering is active, but does not adjust the shutter speed, it only reports the +/- EV compared to correct exposure.

This is how my *istD, K10D and K7D all work with manual aperture K mount lenses. If there is something that the single wheel cameras do differently, let me know as I am only basing those observations on forum member comments.

10-15-2010, 01:33 PM   #39
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I think Violini meant that then he can shoot in Av mode just like with M42 lenses. Without the aperture lever the aperture doesn't stay open when mounted on a cam.
10-15-2010, 02:10 PM   #40
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QuoteOriginally posted by ovim Quote
I think Violini meant that then he can shoot in Av mode just like with M42 lenses. Without the aperture lever the aperture doesn't stay open when mounted on a cam.
I understand he would like to have Av mode and wants the lens to behave like M42, but from a practical point, the green button metering in M mode is the same, with 2 advantages, first you can focus wide open and the camera will stop down to shoot, so you don't have to worry about this yourself, and second, since exposure does not change often between shots, there is no need to have the lens function in stopped down mode, you meter once and are done with it for several shots, until lighting changes.

Even long before digital cameras, when I had cameras with aperture couplings, I would meter off a roadway or path or tree trunk, and stay in manual mode, as opposed to Av mode.

It is so simple once you start, there is no real problem.

Aside from that I don't see the point in damaging a perfectly good lens to make it work in stopped down only mode. At least not a K mount. I would consider it if I was swapping the mount of another system like Canon FD, Minolta MD or Nikon AI, and I have done this, because I sometimes find cheap but good lenses in other mounts and this is a way to use them effectively, but I would never modify a K mount lens, it is just not worth it.
10-15-2010, 04:47 PM   #41
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With my K10 the green button will usually give me at least one stop under exposure. I found that if I opened the lens or used about one stop less exposure than the green button told me, that I was pretty close to the necessary settings. It wasn't erratic but pretty uniform in it's under exposure, so I'd use the green button and subtract a stop, to get very close. Of course I was using the "M" setting, since that's the only setting that works with manual lenses.
10-15-2010, 04:51 PM   #42
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QuoteOriginally posted by jimH Quote
With my K10 the green button will usually give me at least one stop under exposure. I found that if I opened the lens or used about one stop less exposure than the green button told me, that I was pretty close to the necessary settings. It wasn't erratic but pretty uniform in it's under exposure, so I'd use the green button and subtract a stop, to get very close. Of course I was using the "M" setting, since that's the only setting that works with manual lenses.
What lens? I would not expect this with any lens
10-15-2010, 06:12 PM   #43
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I only have 2 manual lenses, M50mm/1.7 and 135/3.5 which I bought with Pentax ME; both the camera and the lenses are in very good condition. Therefore, I better not do any irreversible modification to them. When I find a junk lens, I will go ahead to remove the aperture lever.
10-15-2010, 08:09 PM   #44
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QuoteOriginally posted by violini Quote
I only have 2 manual lenses, M50mm/1.7 and 135/3.5 which I bought with Pentax ME; both the camera and the lenses are in very good condition. Therefore, I better not do any irreversible modification to them. When I find a junk lens, I will go ahead to remove the aperture lever.
I am also one with two manual lenses from the M series, and a recently acquired 55/1.8 Takumar that I have not used very much yet. I find no need to remove pieces from my lenses. I find that generally speaking, a quick stab at the green button on my K10d is only needed when first facing an exposure situation. I may adjust exposure after examining the LCD display - I have blinkies on and check as well multiple histograms when I am in a situation that might be problematic for exposure. Once the lens and shutter are adjusted, there is no further need, and I don't bother with the button any more.
10-17-2010, 01:38 PM   #45
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QuoteOriginally posted by Lowell Goudge Quote
What lens? I would not expect this with any lens
Well the lenses that I have used with the K10 are: M-50 f1.4, M-28 f3.5 and they both seem to do the same thing when it comes to exposure. I kind of misspoke when I said "One stop less exposure" when I meant one stop more exposure. The green button pretty consistently sets the exposure about on stop darker than I like, so I either open the lens one stop or set the shutter on stop slower than recommended by the "green button". With your camera you can do some experimenting, but whatever it does, it should be pretty consistent, so you should be able to work with that.
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