Re: Katz Eye question
On Jun 15, 2008, at 11:54 AM, Boris Liberman wrote: Focusing screens with split image focusing aids are very sensitive to being exactly on the lens optical axis for clean imaging with the focusing aid. I just got a reply from Rachael Katz herself. Boy, that was fast, and it is Sunday! It turns out that if I move my eye to the left and to the right ever so slightly (never thought of this direction) - it helps to bring the darkening to become symmetrical (both top and bottom portions of the split screen) and screen is indeed usable at least at f/8 in moderate tungsten light. I just tried it right now. My understanding is that I did everything properly up to the production tolerances. Most probably, I will simply have to use the screen extensively in order to get used to it. Nonetheless, I couldn't focus my A 50/1.2 at f/1.2 and be sure of the precision of the focus before I bought the screen. So undoubtedly it was worth it. Yes indeed: alignment with the optical axis of the viewfinder system is very critical with some lenses, moving your eye around to find the 'sweet' spot is a good tactic. Rachael is right: use it a while. I'm sure it will work out to be fine for your needs. :-) Godfrey -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
Re: Katz Eye question
From: Boris Liberman [EMAIL PROTECTED] Date: 2008/06/15 Sun AM 04:21:53 GMT To: Pentax-Discuss Mail List pdml@pdml.net Subject: Katz Eye question Hi! I seem to have a problem/issue/strange thing with the K-E screen that I bought. It says (as I asked for it) that it has the optibrite treatment and all such. Now, if I mount that DA 21/3.2 I see that the bottom half circle in the center of the screen is slightly dark. If I mount FAJ 18-35/4.0-5.6 that bottom half becomes seriously dark. I can still use it somewhat for manual focusing but I am more concerned that like this it really intervenes with AF and AE. I am shooting wearing glasses all the time. What have I done wrong? When installing the screen I did not hear the clicking sound when I was locking the filter in place, but I felt that I was closing something very tightly. Also I noticed that the red light for the center AF point is just a bit lower that the center of the split screen circle... Concerned. Boris Difficult to be sure but it does sound as if it is not properly seated. More due to the lack of positive latch than the darkening. This is common with split image prisms. Unless your eye is precisely aligned with it, one side will appear darker. Less alignment, more darkness. This becomes more pronounced as the widest aperture of the lens decreases. - Email sent from www.virginmedia.com/email Virus-checked using McAfee(R) Software and scanned for spam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
Re: Katz Eye question
Focusing screens with split image focusing aids are very sensitive to being exactly on the lens optical axis for clean imaging with the focusing aid. The Pentax K10D's screen retaining hardware and overall tolerances for positioning of the prism to focusing screen has a good deal of potential for inexact alignment. Modest speed, short focal length lenses can aggravate these problems, causing one or the other side of the aid to become darkened. Wearing glasses requires a higher eyepoint as well, relative to the viewfinder optics, which can also have an influence. I've never found the AF LED indicators to be terribly well aligned with the sensing area either but I wouldn't take that as much of a negative. It's issues like these, btw, which are why I have always preferred a simple, plain matte fresnel focusing screen rather than one with focusing aids. The AF sensor system is in the mirror box so this problem to your eye shouldn't affect its operation. However, depending upon how the metering sensors which read from the screen are set up, you might find some variability in the metering. Godfrey On Jun 14, 2008, at 9:21 PM, Boris Liberman wrote: I seem to have a problem/issue/strange thing with the K-E screen that I bought. It says (as I asked for it) that it has the optibrite treatment and all such. Now, if I mount that DA 21/3.2 I see that the bottom half circle in the center of the screen is slightly dark. If I mount FAJ 18-35/4.0-5.6 that bottom half becomes seriously dark. I can still use it somewhat for manual focusing but I am more concerned that like this it really intervenes with AF and AE. I am shooting wearing glasses all the time. What have I done wrong? When installing the screen I did not hear the clicking sound when I was locking the filter in place, but I felt that I was closing something very tightly. Also I noticed that the red light for the center AF point is just a bit lower that the center of the split screen circle... -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
Re: Katz Eye question
It won't affect AF as AF is done lower than focussing screen. It may affect AE however. On Sun, Jun 15, 2008 at 6:21 AM, Boris Liberman [EMAIL PROTECTED] wrote: Hi! I seem to have a problem/issue/strange thing with the K-E screen that I bought. It says (as I asked for it) that it has the optibrite treatment and all such. Now, if I mount that DA 21/3.2 I see that the bottom half circle in the center of the screen is slightly dark. If I mount FAJ 18-35/4.0-5.6 that bottom half becomes seriously dark. I can still use it somewhat for manual focusing but I am more concerned that like this it really intervenes with AF and AE. I am shooting wearing glasses all the time. What have I done wrong? When installing the screen I did not hear the clicking sound when I was locking the filter in place, but I felt that I was closing something very tightly. Also I noticed that the red light for the center AF point is just a bit lower that the center of the split screen circle... Concerned. Boris -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- Thibault Massart aka Thibouille -- Photo: K10D,Z1,SuperA,KX,MX, P30t and KR-10x ;) ... Thinkpad: X23+UB,X60+UB Programing: D7 user (trying out D2007) -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
Re: Katz Eye question
Thanks everyone who responded. I will probably open it one more time and try to realign the screen. Basically, my understanding is that I haven't done much harm. I've googled this issue and it turns out that many people indicate that the AF needs a bit of touch up. And they of course mention those Pentax lenses that allow full time manual focus (quick shift system). At least I will learn something during the process, I hope. Thanks again! -- Boris -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
Re: Katz Eye question
Hi! Godfrey DiGiorgi wrote: Focusing screens with split image focusing aids are very sensitive to being exactly on the lens optical axis for clean imaging with the focusing aid. I just got a reply from Rachael Katz herself. Boy, that was fast, and it is Sunday! It turns out that if I move my eye to the left and to the right ever so slightly (never thought of this direction) - it helps to bring the darkening to become symmetrical (both top and bottom portions of the split screen) and screen is indeed usable at least at f/8 in moderate tungsten light. I just tried it right now. My understanding is that I did everything properly up to the production tolerances. Most probably, I will simply have to use the screen extensively in order to get used to it. Nonetheless, I couldn't focus my A 50/1.2 at f/1.2 and be sure of the precision of the focus before I bought the screen. So undoubtedly it was worth it. Thanks! Boris -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
