[Lance B]

I posted this on DPR as well as here.

A few days ago I posted that the Katz Eye screen fits the K10D which it does but there seems to be an exposure problem. My particular Katz Eye is purely the ground glass screen, has screen has no split prism or microprism collar, only 1/3rd grid lines and a circle around the centre of the screen. Basically it looks the same as the Pentax LL60 screen. I shall tell a bizarre story:

I tried the Katz Eye screen not long after I had the K10D and found that it fitted and decided to use it as I love the 1/3rd grid lines.

So, the next day I go out and start taking photos with various lenses. Tried the FA31, FA50, FA77, FA*28-70, DA16-45, FA*80-200, FA*300 etc to see how they all performed on the K10D. All had excellent exposure except I was getting some seriously underexposed shots with the DA16-45 and also the FA*300. Hmm, maybe the people who were complaining about the DA16-45 underexposing were right after all and I(and Brett St Pierre) were somehow lucky that it worked perfectly for us on our *ist D. I also noticed that I was getting serious underexposure with the FA*300! Hmm, what the hell is going on?

I first dismissed the screen as a possibility as all the other lenses all worked as they did on the *ist D. I then did a series of tests on a white card and my suspicions were vindicated, every lens worked as previously on the *ist D except the DA16-45 and FA*300. They were both underexposing by about 1/2 a stop!

I put a lens on the D and then on the K10D and compared the histograms. All lenses on the D were spot on the middle line of the histogram except the DA16-45, the DA14 and DFA100 macro which were -0.2 to the left of the centre line. The DA/DFA lenses are what I consider perfect exposure and are my most consistent lenses. I believe that -0.2EV to -0.3EV seems to give the most accurate exposure for digital.

All the lenses on the K10D were also spot on the centre line of the histogram excep for the DA16-45 and the FA*300. These two lenses were consistently -0.7EV underexposed. I could not for the life of me work out how ONLY two lenses could be different than the rest when they worked fine on the D. I thought that Pentax must have put the wrong program in the K10D for these two lenses. All sorts of things were running through my head.

In a forlorn hope, I decided to try the LL60 screen to see if it made any difference. After all, it is a genuine Pnetax screen so should be ok. No luck, same problem. F***! I rang Brett to see if he could check his lenses on the K10D and compare them to his *ist D. His K10D worked perfectly with the DA16-45. We checked his procedure and it was the same as mine, so no luck there. I was really begining to think that the K10D was a dud. How could Pentax stuff this up?

I was beginning to run out of ideas and was prepared to try anything and so my last hope was to try the original screen - the LF80 - back in the K10D. What a surprise to find that the DA16-45 and the FA*300 now exposed as they had on my D!! Checked all the other lenses and they too were perfect! All my lenses expose as they should and I am now VERY happy again.

So what the hell was going on? How could a screen affect some lenses and not others??? This is bizarre, don't you think?

I have my own ideas, but I wonder if anyone would like to venture their opinions on this very strange behaviour.

I therefore recommend that you stick with the new "80"(original supplied with the K10D) series screens which have been designed for the K10D. DO NOT use the Katz Eye or the "60" series screens in the K10D.

[wjwncpro]

Hi Lance,
Prior to the DS2 software update, the DA 16-45 underexposed -0.5EV on my DS but with the Katz Eye w/split&grid exposes right on. I took out the Katz Eye a few months ago prior to getting the update and since then (with the update / without the Katz Eye) the 16-45 exposes as should. I just put the Katz Eye back in this past weekend and I'll try to get some pics this Sunday with the 16-45 and see how they come out.

[Lance B]

Hi Lance,
Prior to the DS2 software update, the DA 16-45 underexposed -0.5EV on my DS but with the Katz Eye w/split&grid exposes right on. I took out the Katz Eye a few months ago prior to getting the update and since then (with the update / without the Katz Eye) the 16-45 exposes as should. I just put the Katz Eye back in this past weekend and I'll try to get some pics this Sunday with the 16-45 and see how they come out.

The reason for the Katz Eye exposing correctly on the DS is due to the split prism and microprism collar. I will elaborate.

Brett and I did some extensive testing with the Katz Eye in the D and found that with darker lenses like the DA16-45 f4 and the FA300 f4.5, one half of the split prism, and also each half of the tiny little microprism collar prisms, would go dark. This had the affect of fooling the cameras meter into thinking there was less light than there actually was and so the camera compensated by giving extra exposure. We found that it affected exposure by about 0.7EV.

Spot metering with the Katz Eye was unuseable IMO.

I sold my Katz Eye as it gave too many variable results with the DA16-45 and FA300. I sold it to a forum member who was having underexposure issues with his DS and DA16-45 and it worked for him too.

I think the firmware update for your DS addressed the ORIGINAL underexposure issue and probably made the DS expose correctly like the D does. You may find now that you will have the same problem as Brett and I did with our D.

The DA16-45, like all the new DA/DFA lenses, was one of my most consistently correct exposing lenses. I could always rely on it and I used it as a sort of "standard" by which I judged all other lens exposure. All the FA/FA* lenses generally needed -0.30EV dialled in when used on the D.

The Katz Eye used in the K10D did NOT have any split prism or microprism collar and was effectively just the ground glass screen with 1/3rd grid lines, almost identical to the Pentax LL60 focus screen(which also doesn't work in the K10D). I therefore wonder how it can affect the exposure on just two lenses, but not the others. Maybe the ground glass screen has a slight effect like the Katz Eye with split prism and microprism collar.

[wjwncpro]

I took the Katz eye out of my DS a few months after I got it mainly 'cause it was a pain to keep clean. The split prism and grid would collect a lot of dust in the etchings and getting it clean was 50/50. I did like using the split prism as it was kind of nostalgic and reminded me of my old Minolta XD-11. As far as the lower part going dark, I did not notice it too much unless I was above f11 or with a tc and I shoot mostly MF. That's the way it was for me 30 years ago...

[roscot]

Hi Lance,
I seem to recall reading somewhere that, although the focus screens in the K10 are the same size as the D/DS, they have a new coating on them that is suppose to make them brighter. That would explain why the Katz Eye would render inconsistent readings. It is a bit bizarre that it only shows up on a couple of lenses.

I wonder if the Optibrite coating would make a difference. Anyway, I also read that Katz Optics is looking for someone to volunteer a K10 that they can use to make a screen designed for it. You get a free screen for your trouble.

Thanks for doing the experiment. Saved me the trouble.

-Alan

[Lance B]

Hi Lance,
I seem to recall reading somewhere that, although the focus screens in the K10 are the same size as the D/DS, they have a new coating on them that is suppose to make them brighter. That would explain why the Katz Eye would render inconsistent readings. It is a bit bizarre that it only shows up on a couple of lenses.

This makes sense.

I wonder if the Optibrite coating would make a difference. Anyway, I also read that Katz Optics is looking for someone to volunteer a K10 that they can use to make a screen designed for it. You get a free screen for your trouble.

I wondered the same thing. I also heard that Rachel Katz was looking for a volunteer so she could get a K10D to trial. I would like to help, but being in Austrlalia....

Thanks for doing the experiment. Saved me the trouble.

Not so much an experiment, more so a big mistake.

-Alan

[roscot]

I wondered the same thing. I also heard that Rachel Katz was looking for a volunteer so she could get a K10D to trial. I would like to help, but being in Austrlalia....

-Alan

I would since I like their screens, but since I've only had my toy a week, and haven't really had a chance to actually shoot beyond some testing, no way anyone will pry it from my hands.

[stern]

Hi Lance,
I seem to recall reading somewhere that, although the focus screens in the K10 are the same size as the D/DS, they have a new coating on them that is suppose to make them brighter. That would explain why the Katz Eye would render inconsistent readings.
-Alan

yep! same for me. read it on some german pentax-site. was at a local store here in vienna 2 days ago to order a LL-60 as well as the VF-magnifier (designed for the K10 but compatible with earlier models and) and told the dealer about the different brightnesses of the screens. he phoned up pentax germany to verify this info, got the verification and placed the orders for me. by the way: the new screens cost more than double than old ones (at least here in austria).

cheers,
stern