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.