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04-22-2012, 05:25 AM   #16
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QuoteOriginally posted by kh1234567890 Quote
Maybe one day the moronic Pentax firmware programmers will realise that it would be useful to be able to store exposure calibration offsets linked to lens ID in the camera.
lens transmission has little to do with this - the focusing screen is what is causing the problem. Besides every major photographic lens manufacturer produce lenses that transmit slightly less light than the F numbers indicate - but the light loss is 0.08 of a stop or smaller.

04-22-2012, 10:37 AM   #17
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QuoteOriginally posted by Digitalis Quote
lens transmission has little to do with this - the focusing screen is what is causing the problem. Besides every major photographic lens manufacturer produce lenses that transmit slightly less light than the F numbers indicate - but the light loss is 0.08 of a stop or smaller.
But the brightness of the screen, which is what the viewfinder metering normally measures, varies with the maximum aperture of each lens. It is even worse with variable f zooms where the max aperture changes with the set focal length. All this could be user settable, the fiddle factors seem to be already there but I suspect are actually set for the stock screen and the kit 18-55mm lens.
04-22-2012, 06:28 PM   #18
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QuoteOriginally posted by kh1234567890 Quote
But the brightness of the screen, which is what the viewfinder metering normally measures, varies with the maximum aperture of each lens. It is even worse with variable f zooms where the max aperture changes with the set focal length. All this could be user settable
And that is why we have exposure compensation,though it would be a cumbersome workaround where variable aperture zoom lenses are being used. However most of them only lose a stop of light at either end.And with High DR sensors like the one used in the K-01 and the Pentax K5 one stop is a trivial difference in exposure.
04-22-2012, 09:19 PM   #19
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The whole idea with single lens reflex is to be able to see the actual picture before the photo is taken. And every add-on to this concept should be made to make this idea a reality. Like when you add a switch to preview the depth of field. So when the ‘Live View‘ mode produces better metering than the view finder mode, then I think itīs not good. Then the camera is not really an SLR no more and the single lens reflex view finder becomes an add-on to a digital camera of sorts. I also do shoot short videos from time to time, but if I intended to do more, I would get a dedicated video camera. Or if I preferred to shoot stills and do the focusing based on a live view I could get a 3/4 camera. But I donīt. I prefer a (D)SLR for my stills. We should have a digital LX or something like it (..well—if I had the money—a 645D perhaps).


Last edited by jt_cph_dk; 04-22-2012 at 10:31 PM.
04-22-2012, 10:41 PM - 1 Like   #20
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QuoteOriginally posted by jt_cph_dk Quote
So when the ‘Live View‘ mode produces better metering than the view finder mode, then I think itīs not good
you are being critical of something that you have purposely altered beyond the manufacturers specifications and then you say the whole optical metering system on your camera is no good? If anyone is to blame for a malfunction in the metering of the camera it is you. Not Pentax - they provide a focusing screen with their cameras that typically provide very accurate results, third party focusing screens are known to cause problems because every camera metering system works differently - and have differing levels of sensitivity.

Last edited by Digitalis; 04-23-2012 at 04:45 PM.
04-22-2012, 11:58 PM   #21
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QuoteOriginally posted by Digitalis Quote
you are being critical of something that you have purposely altered beyond the manufacturers specifications and then you say the whole optical metering system on your camera is no good? If anyone is to blame for a malfunction in the metering of the camera it is you. Not Pentax - they provide a focusing screen with their cameras that typically provide very accurate results, third party focusing screens are known to cause problems because every cameras metering systems work differently - and have differing levels of sensitivity.
Well, you are right. However, I donīt know (correct me if Iīm wrong?) that Pentax produces a split prism focusing screen—and when they hang on to K-mount and the old manual focus lenses and provide a green button, they should also make a meter that can handle such a prism since itīs a natural choice with manual focusing. You can simply get more sharp photos with it than without it. I use the auto-focus confirmation and then most often correct it slightly with the split prism.
04-23-2012, 12:31 AM   #22
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What I really want is a DLX, an LX type manual focus digital SLR camera. Where the ‘digital‘ mainly means substituting film as media. I think the problem that I have with the K7 derives from trying to implement to many features into one tool. There are so many, that I hardly ever use (auto-focus, video and lots of tweeking options etc.).
I also think, that the basic choices should be made in-camera, when shooting and would prefer, that there was a much more simple development procedure, than all the required PP that has to be done with RAW files (the so called digital negative? Can we access our files in ten or twenty years?).
I have shifted over to shooting jpgs lately for these reasons.
04-23-2012, 01:55 AM   #23
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QuoteOriginally posted by jt_cph_dk Quote
I also think, that the basic choices should be made in-camera, when shooting and would prefer, that there was a much more simple development procedure, than all the required PP that has to be done with RAW files
I shoot DNG - that certainly keeps things simple. I convert the files into jpeg for web display, Tiff for image editing with a final export to Jpeg or for printing. I use several cameras that used DNG K7,K5,645D Leica M8.2 and M9 - that my Nikon and Canon DSLR cameras* are in the minority, my workflow with DNG is not all that different from my cameras that do not have a DNG raw file option Lightroom does a good job with all formats.

*I use the Nikon D3s and D300s I also use the Canon 1Ds MKIII, 1D MkII N and 20D

04-23-2012, 02:43 AM   #24
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QuoteOriginally posted by Digitalis Quote
I shoot DNG - that certainly keeps things simple. I convert the files into jpeg for web display, Tiff for image editing with a final export to Jpeg or for printing. I use several cameras that used DNG K7,K5,645D Leica M8.2 and M9 - that my Nikon and Canon DSLR cameras* are in the minority, my workflow with DNG is not all that different from my cameras that do not have a DNG raw file option Lightroom does a good job with all formats.

*I use the Nikon D3s and D300s I also use the Canon 1Ds MKIII, 1D MkII N and 20D
You sure have been around some digital cameras. That 645D is one I would really like to try out. I use the Pentax 67 system instead. I ‘only‘ own one DA Ltd — the 2.8/40 and the rest is all manual primes except for a Kit 18-55. I donīt know your lens line-up? But the old ones does set some limits to convenience with the K7.
And what works for you is just fine by me. Iīm keen on hearing details on your workflow, because although I have some 15 years of professional experience as a graphic designer/artist I have only been using DSLRs/PEFs/DNGs for about a year. So there is probably much to learn. As it is, I find my self spending half the time in front of my Mac instead of out there shooting, when I do DNGs. So, I enjoy my photography work very much, when I get print-ready results (7mb Adobe1998 jpgs) straight out of the camera. When I donīt have to make image quality/color/crop/etc. decisions post-shooting. This is why I started the thread in the first place. I want to setup the camera to do this. Thankīs
04-23-2012, 04:19 AM   #25
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QuoteOriginally posted by Digitalis Quote
you are being critical of something that you have purposely altered beyond the manufacturers specifications and then you say the whole optical metering system on your camera is no good? If anyone is to blame for a malfunction in the metering of the camera it is you. Not Pentax - they provide a focusing screen with their cameras that typically provide very accurate results, third party focusing screens are known to cause problems because every cameras metering systems work differently - and have differing levels of sensitivity.
Complete rubbish. The viewfinder metering system is a hangover kludge from the days of film (it never worked well even then, that's why Olympus gave up on it) and should have been ditched ages ago. It is hit-and-miss even with the stock screen.
04-23-2012, 05:38 AM   #26
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QuoteOriginally posted by kh1234567890 Quote
Complete rubbish. The viewfinder metering system is a hangover kludge from the days of film (it never worked well even then, that's why Olympus gave up on it) and should have been ditched ages ago. It is hit-and-miss even with the stock screen.
Well that is too bad, it is what we are stuck with. I have used many, many cameras from different makers over the years and I have found common SLR metering systems to be perfectly satisfactory for 90% of situations encountered during daylight hours. You know, even off the sensor AE metering systems can be fooled. There is no such thing as a perfect metering system and if you think you are in any position to be critical of the tried and true - then I challenge you to come up with a perfect AE metering system that gives perfect results 100% of the time without fail.

Last edited by Digitalis; 04-23-2012 at 05:54 AM.
04-23-2012, 06:18 AM   #27
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I find the LX meter magnificent. It delivers more than correct and actually interesting in-it-self measurements. Especially in difficult low light. But more than that, I also find that it is ‘charming‘ — it reaches out to you — and, that my photographic ideas about a given scenery are easily put into reality. For instance through making a couple of measurements and adding some personal, perhaps creative preferences. Simple. With great results. Even when exchanging the lens mid-session, it will still deliver. It is completely reliable. This is not the case with the K7. At least not when using ‘old‘ lenses. I think.
04-23-2012, 06:37 AM   #28
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Although I do not use my K7 or K5 regularly at this time with legacy lenses, I think I can help you understand the issue, and also the ways to work around it.

First of all, pentax DSLRs do not have inconsistent metering,

I say this because once you do some simple tests, you will find that the metering, while perhaps not correct, is very consistent in its errors.

To aid in this discussion, I have attached a chart that is very well known in the forums, which I really should update to include legacy lenses as well, but just have not had the time.



This is for K mounts, but shows for most of the flagship models (K20 missing but assumed identical to K10D) the performance with 50 mm lenses.

This is common for all focal lengths and leads me to believe that the metering is dependant on the true aperture of the lens, and therefore when an A lens is used, the camera corrects for the open aperture behavior

This also leads to errors when using teleconverters, which is how this whole thing came about.

To compound this issue, when using legacy lenses, which do not short any pins, there is, a model to model difference in some offsets in exposure that can be present. some models require an exposure compensation of 1-2 stops, and this may also change between manual mode and Av mode when using M42 lenses/

My advise is to use a block wall, paved road or other similarly uniform color, uniformly lit surface and map the performance of your metering system. once it is known, you will not have issues. As a simple point, if you shoot at F5.6 you will meter with the most consistency, I suspect this is because the kit lenses are all F4-5.6 lenses
04-23-2012, 09:36 AM   #29
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QuoteOriginally posted by jt_cph_dk Quote
I find the LX meter magnificent. It delivers more than correct and actually interesting in-it-self measurements. Especially in difficult low light. But more than that, I also find that it is ‘charming‘ — it reaches out to you — and, that my photographic ideas about a given scenery are easily put into reality. For instance through making a couple of measurements and adding some personal, perhaps creative preferences. Simple. With great results. Even when exchanging the lens mid-session, it will still deliver. It is completely reliable. This is not the case with the K7. At least not when using ‘old‘ lenses. I think.
The LX used off the film metering, Pentax answer to Olympus. Took them years to work round the patents. Not so easy to do with a shiny sensor instead of film though.
04-23-2012, 04:17 PM   #30
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QuoteOriginally posted by Lowell Goudge Quote
This is common for all focal lengths and leads me to believe that the metering is dependant on the true aperture of the lens, and therefore when an A lens is used, the camera corrects for the open aperture behavior
Hello Lowell, Thankīs for posting your chart.

I donīt get this meter? With any given lens and aperture, it is supposed to measure the amount of light that comes through to the sensor calculating the time and/or ISO needed for a correct exposure. Then from that and for my reasons, I can then choose to over- or under-expose the whole or parts of the scene. However, and as your chart shows, This meter does not deliver consistent results regardless of what ever aperture setting I choose (I have made the test shots going through all the steps) but instead comes up with a fluctuating (or inconsistent) result as described earlier. Then Iīm told itīs the split prism. And I can understand that. This needs calibration. But I still donīt get why there is a kind of algorithmic disorder. Why is it not the same for every step of aperture, if the problem derives from the split prism being added to the flow of light?

I know how to work around it and get the results that I want, but I find it inconvenient to have to do so every time I change the aperture. Itīs supposed to be enough to push the green button when in M mode and should be manual (by switch) in Av mode with the Takumars.

Last edited by jt_cph_dk; 04-23-2012 at 05:29 PM.
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