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06-05-2014, 08:46 PM - 3 Likes   #1
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Pentax K-3 Compatibility with S type Focus Screen

The S type focus screen (cut-down Canon ee-S) from focusingscreen.com is a favorite of manual focus fans here on Pentax Forums and is highly praised by those that use it. In fact, I don't know that I recall a single review, post, or comment that indicated dissatisfaction with the screen. As a result, it was with a good deal of eager anticipation that I ordered the S type screen with AF frame lines for my yet to be delivered K-3. I have had a very good run with the Katz Eye screen on my K10D, but have found the focus aides to be a distraction and a bother when doing close-up and macro work. The S type screen promised accurate and snappy natural focus along with realistic DOF rendering. Cool!

Although delivery took some time, I was very pleased to find everything exactly as my fellow forum members described, right down to the little finger-cots. Installation was a simple matter and soon I was happily assessing whether the glowing reports were true. Are they? In a word, yes. The viewfinder image was bright, images snapped into focus, DOF was true, and the field was wonderfully free of distraction. One thing that surprised me was the AF frame lines. I had expected the usual fine dark etching as with the stock screen. Instead the lines appear to be laser-scribed and are a broad bright-line as opposed to fine dark line. The lines reminded me of the albedo bright frame lines on many rangefinder cameras. It struck me that the lines appeared to be VERY bright in some light, but I dismissed my concerns.

I spent a couple of weeks using the K-3, usually with my new Sigma 17-70/2.8-4 HSM (C) and occasionally with my FA 35/2 and other fairly fast lenses. It was so nice to focus easily with those wide aperture lenses. The honeymoon came to an abrupt halt a couple of weeks ago when I decided to see how dim the finder is with a somewhat slower lens, say the DA 18-55/3.5-5.6.

The 18-55 kit is usable with the Katz Eye screen, but a little too dim for the microprism. I expected similar dimness with the S type screen. Sure enough, the view was dim, but still usable. I then took a couple of test shots including a meter evaluation of a blank wall. I was expecting mild overexposure and was alarmed to see that all of the test shots were severely underexposed. The blank wall exposure settings were a full 2 1/2 stops below a live-view metering of the same wall. I then put my FA 35/2 on the camera and repeated the experiment. All shots were properly exposed and the blank wall exposure agreed with the live view exposure. Wow, that was unexpected. Neither lens had ever given me poor exposure readings on the K10D.

I took the camera out into the field for some real shooting that weekend and was disappointed that about half my frames taken with the Sigma 17-70 were similarly about 2 stops underexposed. The underexposed frames appeared to mostly be of low contrast subjects. Bummer

Cut to the chase

I decided to do a controlled test of viewfinder metering vs. live view using both my DA 18-55 and FA 35/2. The basic setup was shooting through the white cellular blinds of my north-facing breakfast nook with the light being supplied by mid-afternoon sky (no direct sun) on a cloudless day. The intent was to provide even luminance of moderate intensity with daylight color balance. Several exposures were done within the span of a few minutes. General setting were Av mode, f/8, ISO 100, matrix metering with camera on tripod and the lens manually focused on the surface of the blinds. Eyepiece was shielded (thumb) before exposure. No exposure compensation was applied.

First, here are the results for the FA 35/2:
  • Pentax-FA 35/2 lens
  • Metered shutter speed using the viewfinder exposure meter: 1/15s
  • Metered shutter speed using the live view metering: 1/13s
Note the close agreement between the viewfinder and live view metering. This is a very acceptable result and what I would expect.

Now, here are the results for the DA 18-55:
  • Pentax-DA 18-55/3.5-5.6 @ 35mm focal length
  • Metered shutter speed using the viewfinder exposure meter: 1/50s
  • Metered shutter speed using the live view metering: 1/15s
Notice that the viewfinder meter using the S-type screen indicates 2 stops less exposure with the relatively slow 18-55 zoom than the meter reading from the live view sensor using the same lens. The live view exposure is in agreement with the results from the faster FA 35/2 lens.

For those unclear of the setup:




What happened?

My theory at this time is that the laser-etched bright frames are interacting in an unexpected way with the K-3's new high-density 86,000 pixel RGB viewfinder metering system not found in earlier Pentax models. That would explain why users on the K-5, K-30 and other cameras have not encountered this problem. I believe that the bright lines bias the meter for certain types of subjects. Here is a very poor photograph through the viewfinder with the DA 18-55 mounted:



To the eye the lines are strikingly bright relative to the even background. I did some careful observance in general shooting and noticed that the contrast between the frame lines and the subject varied according to the scene. with complex, high contrast subjects the frame lines are fairly indistinct. With low contrast subjects the lines fairly pop.

Conclusion and advice:

I was not able to find a work-around that would allow predictable metering with the S type screen on my K-3. Even maximum apertures as wide as f/2.8 could result in unanticipated severe underexposure. I finally reverted to the stock focus screen on the K-3 and have not decided what to do with the S type screen. With the stock screen installed, exposure meter behavior has returned to normal, meaning excellent.

Based on my experience, I would strongly advise K-3 owners against purchase of the S type screen with AF frame lines from focusingscreen.com. They make a good product, but apparently have not tested this particular screen on the K-3 camera. If you do purchase and find you are having problems similar to mine, they will not accept a return. I know. I tried. Their answer was that I should know before I buy whether the product is appropriate for my camera.

FAQ:
  • Which focusingscreen.com screens are affected? I found this problem with the S type screen equipped with the optional AF frame lines. Other screens may be affected, but there is no evidence to date this is so.
  • Is there a problem with other Pentax dSLRs? To the best of knowledge, there are no similar reports with the K-5, K-30, K-50, or any of the other bodies that are listed as compatible with this screen model.
  • Has focusingscreen.com proposed a solution or offered a recall? No, focusingscreen.com has indicated that this is a user problem and that they bear no responsibility.
  • Is this just you who has noticed this problem? There are a few other reports that were part of the comment thread: https://www.pentaxforums.com/forums/115-pentax-k-5/142241-best-screen-ever-ma...n-ee-s-43.html

For anyone who is interested, this report pains me somewhat. I am not in the habit of whining about gear or the shortcomings of kit that does not meet my specific need. I do however feel that it is a reasonable expectation that a fairly expensive accessory should not seriously compromise basic camera functions. It is in the spirit of bringing this issue to the attention of other K-3 users, that I make this post.

Steve


Last edited by stevebrot; 06-05-2014 at 10:03 PM.
06-05-2014, 08:58 PM   #2
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It's a shame they would not accept a return. "User Problem"? Hardly.

I was contemplating buying a screen for my K-3, but focusingscreen.com will not be the one to get my money...
06-05-2014, 09:11 PM   #3
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QuoteOriginally posted by OregonJim Quote
It's a shame they would not accept a return. "User Problem"? Hardly.

I was contemplating buying a screen for my K-3, but focusingscreen.com will not be the one to get my money...
I am sorry too. I have referred many users on this site to focusingscreen.com and had considered them to be a reputable dealer. I was hoping they would have thanked me for bringing this issue to their attention, but the message they sent me indicated that they saw no need to change what they sell for the K-3.

Again, while I might not be happy with focusingscreen.com, my major concern is that K-3 owners not have my experience. If I had not done the research, I would likely be negotiating a return of my camera on warranty as defective instead of just reverting the screen.


Steve
06-05-2014, 10:06 PM - 1 Like   #4
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Well, I understand your issue a little better now. I buy that there could be an issue with the frame-line-equipped s-screen and the new metering system on the K-3. In the other thread I mistakenly thought you were saying that the problem existed with all bodies.

As you know, my screen in my K-3 has no markings so I can't do an apples-to-apples comparison, and my screen in my K-5IIs has the grid lines, not AF area markings, so those are still not really in the same part of the screen. Plus, that screen required shimming so I'm not really eager to do a swap.

It is unfortunate that you had to find this out the hard way, especially since it seems to have been substantiated by another. I still understand the seller not wanting to offer a return on such a delicate item, but I agree that he should be willing to put a notation on his site about this particular combo. Of course, we all know that customer relations are a weak point with him, so I guess it's not too surprising.

Anywho, kudos for a fair assessment of the screen and your situation and for the heads-up to others.

06-06-2014, 05:49 AM   #5
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Bummer.

Without having done any systematic testing, I have noticed occasional underexposure (about 1 stop) with my K-5 with a screen with AF area markings. It seems to happen mostly in very bright scenes with slow lenses; I first noticed it with pictures taken with the kit lens in the harsh midday light in open landscapes in Namibia. Can't see any problems in (for me) more normal/mixed scenes or with faster lenses.

Again, I haven't really looked into it as I can live well with a 1 stop underexposure in bright scenes.

Thanks for the heads-up - something to think about should a K-3 find its way to me.
06-06-2014, 05:59 AM   #6
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Excellent write up of this issue, which I am unfortunate enough to be experiencing myself.

I also have the AF etched screen in a K-3. I have a k-5 and will swap put my k-3 into that camera, and see if I still have the exposure problems.

---------- Post added 06-06-14 at 06:05 AM ----------

QuoteOriginally posted by savoche Quote
Again, I haven't really looked into it as I can live well with a 1 stop underexposure in bright scenes.

Thanks for the heads-up - something to think about should a K-3 find its way to me.
It would be great if you could do a quick check on your k-5 and verify if you have the same issue. If you mount a slow lens an point it against a even colored wall it is as simple as switching to Av and getting the exposure normally and then via live view (which of course by passes the screen). We are seeing a 1-2 stop difference immediately.

And it would be REALLY great to see PF members with a NON etched screen do the same test, and see what results they get.

Last edited by HenrikDK; 06-06-2014 at 06:26 AM.
06-06-2014, 07:48 AM   #7
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Thanks for the comments. I would not have posted except that the S type screen is so highly regarded and it was such a disappointment that it did not work well with my K-3.


Steve
06-06-2014, 11:00 AM   #8
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QuoteOriginally posted by stevebrot Quote
Thanks for the comments. I would not have posted except that the S type screen is so highly regarded and it was such a disappointment that it did not work well with my K-3.


Steve
Thanks for the write up indeed! I have been having quite severe underexposure issues with the K3 and the sigma 500/4.5 on the pentax 1.4x tc. The really hard thing (up to a point also with other lenses) is the exposure inconsistency. Against bright (blue) skies, the underexposure requires more than +2ev compensation, but in flat lighting perhaps only +0,6ev.
And considering that I was really impressed with the K3's metering when I first got it (and still had the stock screen in it) this is saying a lot.
Since my s-type screen (from focusingscreens.com with AF markings) was damaged when switching it from the K5 to the K5IIs, I wanted to order a new one, but have been held off by the exposure issues. As I have four Zeiss ZK manual focus lenses, switching back to the stock screen was no option.
Thanks to your post, I today ordered a new s-type screen, but this time without the AF markings, that are not important to me anyway.
I hope that with the new screen especially the bad underexposures against bright light will be gone.

regards
Chris

06-06-2014, 11:25 AM   #9
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QuoteOriginally posted by HenrikDK Quote
It would be great if you could do a quick check on your k-5 and verify if you have the same issue. If you mount a slow lens an point it against a even colored wall it is as simple as switching to Av and getting the exposure normally and then via live view (which of course by passes the screen). We are seeing a 1-2 stop difference immediately.
I'll see if I can get around to doing that. I'm going to be away from home a lot so it might take a bit.

QuoteQuote:
And it would be REALLY great to see PF members with a NON etched screen do the same test, and see what results they get.
Definitely!
06-06-2014, 11:41 AM   #10
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QuoteOriginally posted by Chris Mak Quote
Thanks to your post, I today ordered a new s-type screen, but this time without the AF markings, that are not important to me anyway.
If I were you I would cancel the order and wait until someone with a blank screen tests. There was another PF member with a K10 and a blank s screen that appeared to have underexposure issues as well, though it was a little unclear. In other words I am not sure our theory of the AF markings holds or not, though it seems like a very plausible and likely explanation.

I suspect (hope) there will be someone testing a non-etched screen in the next few days...

Last edited by HenrikDK; 06-06-2014 at 11:47 AM.
06-06-2014, 12:33 PM   #11
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QuoteOriginally posted by HenrikDK Quote
If I were you I would cancel the order and wait until someone with a blank screen tests. There was another PF member with a K10 and a blank s screen that appeared to have underexposure issues as well, though it was a little unclear. In other words I am not sure our theory of the AF markings holds or not, though it seems like a very plausible and likely explanation.

I suspect (hope) there will be someone testing a non-etched screen in the next few days...
I don't really have any other option, as my main lenses are all MF and f2, and going back to the stock screen is no option. Besides, underexposure can easily be compensated for, it's the exposure inconsistency that is the real problem, the brighter the view, the more the K3 underexposes. If that is caused by the etched AF markings (and that does seem plausible), than that problem should be solved. If not, that would mean constantly having the finger on the exposure compensation dial.
06-06-2014, 06:50 PM   #12
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QuoteOriginally posted by Chris Mak Quote
I don't really have any other option, as my main lenses are all MF and f2, and going back to the stock screen is no option. Besides, underexposure can easily be compensated for, it's the exposure inconsistency that is the real problem, the brighter the view, the more the K3 underexposes. If that is caused by the etched AF markings (and that does seem plausible), than that problem should be solved. If not, that would mean constantly having the finger on the exposure compensation dial.
Please let us know how the new screen behaves. I also have one with AF markings and my metering is often off.
06-11-2014, 08:00 PM   #13
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So yesterday I moved my EE-S screen from my K-3 to my K-5. Put on one of my slow lenses, and voila - my exposure via the view finder now matches live view! Well - it was of slightly by 1/3 of a stop or so, but that is no more than the stock screen.

EXCELLENT! Threw on my FA31 just to check.... ARGHHHHHH

Now my fast lens is over exposing. Sometimes exposure is OK, but most of the time it is over by half to one stop, and often more than that. Unfortunately I can't see any rhyme or reason for when it happens, though it generally involve light/bright areas Tried it in daylight again today - same thing. Center weight does not make it any better - in some instances makes it worse.

Under exposure, especially for slower lenses, I can tolerate. There you at least have a good chance of recovering. Overexposure on the other hand.... Once you blow those highlights...

I should add that my screen have the AF etchings. However, when I see the over exposure, the etchings do NOT stand out as it did with the under exposure on my K-3
07-09-2014, 06:28 PM   #14
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Interesting resource at focusingscreen.com

I don't know why I did not see this before, but focusingscreen.com provides a page detailing how the grid lines are made and how they appear at different lens aperture settings.

Very interesting...

Focusing Screen--Grid focusing screens


Steve
07-10-2014, 02:08 PM   #15
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I guess all the high praise for the screens are for unmarked ones?

I never got a screen for my K5 because I had one in my K10d that was horrible for exposure. Now I'm thinking of a K3, and would like something a bit more reliable than the stock screen, but not necessarily at the expense of exposure. I mostly shoot AF anyway, although I'd like to pick up a few more older A or M lenses.
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