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04-18-2019, 09:38 PM - 1 Like   #16
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QuoteOriginally posted by dms Quote
As a happy accident, this means if you set your exposure by spot metering the brightest area in the scene, no exposure adjustment is required at f/5.6 and above.
Are you talking maximum aperture with open-aperture metering or metered aperture with stop-down metering? If stop-down, even the Nikon K3 will begin to black-out at or near f/8. I would expect severe problems when that is the case.


Steve

(...we be soooo off topic... ...maybe not, but just seems that way...)

04-18-2019, 10:18 PM - 1 Like   #17
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QuoteOriginally posted by stevebrot Quote
Are you talking maximum aperture with open-aperture metering or metered aperture with stop-down metering? If stop-down, even the Nikon K3 will begin to black-out at or near f/8. I would expect severe problems when that is the case.


Steve

(...we be soooo off topic... ...maybe not, but just seems that way...)
It was both, A lens if the open-aperture reading and K lens if stop down, as It is the aperture at which the exposure determination is being made, and not the aperture that will be used, that determines the exposure adjustment. You may be right about the blacking out at f/8, I only really used the spot metering for theatre photo's and in that scenario I was never closed more than f/5.6, and usually f/4.

As regards off topic, there was (were) comments about the debit side of the replacement screen being the inability to use spot metering reliably. My point is to say it still can be used, with some additional adjustment.
04-19-2019, 03:48 AM - 1 Like   #18
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The Canon AE-1 had something called "split image focusing", in which a circle drawn in the center of the viewfinder's image was split horizontally, and you could tell when you've got the focus right when the two halves matched up. Really, the precursor to contrast-based AF. But I wish I could have that in my Pentax cameras, because it worked better than anything else I've ever seen.
04-19-2019, 03:51 AM - 1 Like   #19
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That's what some of us have, and what we have been discussing messing up the spot auto exposure - mine is diagonal rather than horizontal though.

04-19-2019, 04:12 AM - 3 Likes   #20
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I have not read through all the responses above, so I may be repeating something or stating common knowledge, BUT, when adjusting the eyepiece diopter remember to focus on the focusing screen, not the image. In fact, either twist the lens far out of focus or remove the lens entirely when adjusting the diopter so you can concentrate on the surface of the focusing screen.
04-19-2019, 04:29 AM - 2 Likes   #21
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QuoteOriginally posted by dlh Quote
But I wish I could have that in my Pentax cameras
Any Pentax camera with a removable focus screen can have a split prism screen. i had one in my DS and K10D.
04-19-2019, 05:37 AM - 1 Like   #22
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thanks for the tip; after a bit of searching, I ordered a couple of screens from:
Focusing Screen in Taiwan R.O.C.; two hundred bucks incl. shipping.

04-19-2019, 05:50 AM - 1 Like   #23
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live view ... slow but sure http://www.pentaxerostore.info/pentax/upload/14/05/121420002jpg.jpg
05-02-2019, 12:23 PM - 1 Like   #24
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QuoteOriginally posted by dlh Quote
thanks for the tip; after a bit of searching, I ordered a couple of screens from:
Focusing Screen in Taiwan R.O.C.; two hundred bucks incl. shipping.
Installed the first in the K-50 this morning. Installation was a snap, as long as one is careful to observe which side is up and which side the tab is on, prior to fully removing the old screen. Nowhere near as complicated as, say, rebuilding a Rochester Quadrajet. Testing for front-to-back focus showed no adjustment needed - picture of a typesize guage below, focus was on the six-inch point. There were two things that bothered me - first, "focusingscreen.com" is in Taiwan, and their English needs a lot of work - the instructions are pretty much unintelligible. Secondly, they say they need ten-day turnaround because the screens are "custom-made to order". What I got were screens in standard Canon packaging; they had sticky labels attached showing which Pentax camera they were for, but either they're not "custom made" or they're trademark knock-offs. My guess is the former, they're probably drop-shipping from a Canon distributor or something. The difference is that if you know what to look for, you can order the same thing off Canon's website for a third the cost.

However, I didn't know what I was looking for, and it was worth the extra cost not to have to think about it. Summation: I'm happy, it's a terrific improvement over the original screen.

I'm a mostly-manual guy, generally put up with live view and autofocus but I hate 'em. So the improved split-image prismatic or whatever it is, is an enormous relief, improves the utility of the camera many multiples.

Last edited by Unregistered User; 10-01-2019 at 07:56 AM.
05-02-2019, 01:46 PM - 2 Likes   #25
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QuoteOriginally posted by dlh Quote
What I got were screens in standard Canon packaging; they had sticky labels attached showing which Pentax camera they were for, but either they're not "custom made" or they're trademark knock-offs.
They are cut down from Canon product intended for their FF dSLRs and made to order.


Steve
05-04-2019, 04:19 AM - 1 Like   #26
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QuoteOriginally posted by stevebrot Quote
They are cut down from Canon product intended for their FF dSLRs and made to order.

Steve
Thanks for that. Another update. Installing the second of the two I'd bought, this one in a K-1, was a bit more work. The metal 0.185" shim in the camera was too thick, so I replaced that with the thicker of the two plastic shims supplied, but it took several tries to get the thing back together because the plastic kept slipping around as I closed the latch. Then I had to put little stickers (supplied) on a couple of the edges to get the center lined up properly. Finally got it almost damn-near perfect. I say "almost", because, with a 100mm macro lens with the aperture wide open (shallowest possible depth of field), the focus is still slightly off - back-focusing about 6mm off at about six feet. That's probably close enough for most of the stuff I do (greater depth of field will take care of it with most of the lenses I use), but I figure to see if I can get me a package of metal shims in appropriate thicknesses. Let me know, please, if you know of such a thing.
05-04-2019, 04:48 AM   #27
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QuoteOriginally posted by dlh Quote
Thanks for that. Another update. Installing the second of the two I'd bought, this one in a K-1, was a bit more work. The metal 0.185" shim in the camera was too thick, so I replaced that with the thicker of the two plastic shims supplied, but it took several tries to get the thing back together because the plastic kept slipping around as I closed the latch. Then I had to put little stickers (supplied) on a couple of the edges to get the center lined up properly. Finally got it almost damn-near perfect. I say "almost", because, with a 100mm macro lens with the aperture wide open (shallowest possible depth of field), the focus is still slightly off - back-focusing about 6mm off at about six feet. That's probably close enough for most of the stuff I do (greater depth of field will take care of it with most of the lenses I use), but I figure to see if I can get me a package of metal shims in appropriate thicknesses. Let me know, please, if you know of such a thing.
One thing you could try is to use the AF/FA menu to adjust the focus to compensate for that backfocus **. If the 100mm macro is a manual lens you can use the "APPLY ALL" setting. This will further require you to AF/FA any autofocus lenses you have using the "APPLY ONE" setting (even if you leave it at "0") otherwise you will find those lenses may be corrected too depending on your menu setting. Let me know if you want to try this and I can go into more detail.


** There is one thing I am not 100% sure about and perhaps someone else can chip in here. I have always assumed that the AF/FA adjustment worked by moving the sensor backwards or forwards rather than moving the AF module. If I am wrong then this wont work at all.
05-04-2019, 05:06 AM - 1 Like   #28
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QuoteOriginally posted by BigMackCam Quote
How do you find accuracy of the various metering modes with the replacement screen? I found I could get away with matrix metering (with some adjustments, depending on the scene), less so with centre-weighted, and all bets were off with spot metering. It was metering inaccuracies that eventually caused me to revert to the original screen...
This is 100% spot on.

I use a split image finder in the k10:also

Mine is from jinfinance, and is a a dual split image. As others have mentioned you should set the diopter to see clearly the focusing screen.

Last edited by Lowell Goudge; 05-04-2019 at 06:13 AM.
05-05-2019, 12:22 PM - 2 Likes   #29
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Since my (previous and only) post regarding focusing non-automatic lenses on my K10 Pentax, I have been amazed at the informed and erudite discourses that I have unwittingly provoked. As I said, I’ve always had a love for, and admiration of, slightly out of date technology and to prove the point I have just acquired a Voigtlander Vito B. My previous and other dSlr, and I’m sorry to use the C word, is a Canon 50d, another weighty dinosaur of a camera. I am nowhere near as well-versed in digital Slr science as you people so when I bought my 50d, I was able to buy a really excellent book by DavidBusch who takes the reader by the hand and leads him step by step through the argot to a clearer understanding. Is there a book on my Pentax that will do the same? The custom settings are a case in point: AF Button Function 3, Centre of AF point. Is this a duplication of the Auto Focus Switching Dial?
Let me say now that I’ve been most impressed with you all and, incidentally, by your excellent use of good grammatical English so lacking in many forums. I shall follow your further remarks with great interest.
05-05-2019, 02:45 PM - 1 Like   #30
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QuoteOriginally posted by pschlute Quote
I have always assumed that the AF/FA adjustment worked by moving the sensor backwards or forwards rather than moving the AF module. If I am wrong then this wont work at all.
That is not how it works. The physical components of the image sensor and the PDAF sensor and its mirrors/lenses stay exactly as they were placed at the factory. Unfortunately, full explanation of how it does work would take several pages and multiple diagrams. The summary version is that AF fine adjustment is required when the contrast blur at a line boundary is asymmetrical with or without ambiguity (low peak or no clear peak). The fine adjust applies a numeric correction to the detected curve so that the detector acts as if it were more one way or the other. Whether that correction works well at all distances, in all light, and at all focal lengths may be true in many (most?) cases, but may not with a number of lenses. For example, Sigma supports AF fine-tune on the lens side using the USB dock device. I don't have a clue as to how it works since the body will grind away at its end until it gets a clear maximum signal near the detection array's center point. The important point is that a Sigma zoom will usually require adjustments at several different focal lengths and several distances for each focal length. Ideally, the in-body tune should work similarly, but that is not the case.


Steve

Last edited by stevebrot; 05-05-2019 at 03:05 PM.
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