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03-11-2016, 01:12 PM   #1
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The Misadventures of a Pentax Noob (humor)

I previously owned a K-01 and enjoyed it, but I found that no matter how careful I was, I had trouble using my manual focus 50mm f:2 lens with it. Phase detection is a great step in aiding focus, but it never seemed to quite work for me.

I remembered using the old split prism focus screens on regular SLR cameras back in high school photography in the late 1980s. While it took a little longer for me to focus, I always had tack sharp focus on whatever I aimed at.

I set out on a misguided quest to replace the stock focus screen of my recently acquired K10D with a split prism focus screen. The main determinations were price and time. It came down to picking between eBay, focusingscreens.com or Amazon. I’d dealt with Fotodiox via Amazon before when I replaced the stock focusing screens in my old Nikons and they’d worked beautifully every time. The other advantage was the price of about $20 on Amazon versus $70 from focusingscreens.com. The last point for me was the wait time—I’m notorious for my lack of patience.

So off to Amazon I went and I order the screen. It arrived a few days later and I set to work.

After installing it, I found that instead of the sharp focus I’d expected when I lined everything up plus getting the green confirmation dot in the viewfinder, I found that I had a problem with front focus. Ok, I can deal with this. I printed out a cute little camera target and focusing ruler, glued and assembled it and carefully set everything up to begin the process of correcting the front focus issue.

Then I found that I had updated the K10D to the latest firmware and there wasn’t any debugging menu anymore. Whoops! So the next few hours were spent chasing down options on rolling back the firmware. I finally ran down the necessary files, installed them into the camera and tricked it into rolling back the firmware. All on a Mac no less! I then saved those buggers to my Dropbox in case I ever needed them again.

After several frustrating misses of accessing the elusive debugging option, I finally was able to tap in the sequence quickly enough to start it. Yes!

Then the next few days of agony began.

I could never seem to get the 50mm lens to work quite right. I’d finally think I had reached the sweet spot as I carefully dialed in the focusing adjustments, reaching the perfect focus, only to find that suddenly I couldn’t get any kind of sharp focus at infinity or that while it worked in the focusing tests, in the real world, it was still front focusing. I began to lose my grip on my sanity as I started over.

By this point, I started to look at my manual focus 50mm lens with a more jaundiced eye and began to question my desire to work with it. Sure the regular 35-80mm f:4-5.6 was adequate but it also had AUTO FOCUS and I was starting to think the old-fashioned way of doing things might not be so great anymore. But then another little voice would argue that the 50mm had a better light capture quality and could impart superior sharpness in my photos where I wanted it. So I trudged on.

I finally had a moment of brilliance and tried a few other lenses. Naturally they didn’t work quite right anymore either. Not at least until I zeroed out my adjustments in the debugging menu. Then they’d focus, but it took them more time than before and the focus was ever so slightly off. I tried using the split screen manual focus option but it was still the same problem.

I finally swapped the focusing screens again and tried everything out. With the stock focusing screen, my autofocus lenses hunted far less and gave me sharp results again. With the 50mm manual, I was back to a slightly softened, out of focus result no matter what aperture I tried, no matter that the focusing confirmation dot came on.

At this point, after resisting the urge to smash the old manual focus lens with a sledgehammer while speaking in tongues, I’ve begun to see the light and embrace autofocus lenses in spite of their higher prices. Sorry manual focus lenses, for the sake of my sanity, we can’t play together anymore.

03-11-2016, 03:30 PM - 1 Like   #2
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Welcome to the forum and thank you for a very interesting introduction.
03-11-2016, 05:16 PM - 1 Like   #3
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One of the problems with DSLRs is that they get focus in a way that uses a light path that isn't the same as the sensor path. This means that you have to shim the screen very precisely. Typically with a modern DSLR with live view you can use to double check the focus.
03-11-2016, 05:31 PM - 1 Like   #4
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Unfortunately, you didn't shim it properly, Jerry. :-(

03-12-2016, 12:49 PM   #5
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QuoteOriginally posted by UncleVanya Quote
One of the problems with DSLRs is that they get focus in a way that uses a light path that isn't the same as the sensor path. This means that you have to shim the screen very precisely. Typically with a modern DSLR with live view you can use to double check the focus.
I've started to realize that. What I don't know about shimming could fill a book at this point. I might come back to this little project in the future once I've gained more confidence and done more research to familiarize myself with shimming.

I just came back from my yearly visit with my eye doctor. I like to joke that I've joined the Geritol generation as I now need bifocals. I wonder if my issues with manual focusing will improve once I get my new glasses?

---------- Post added 03-12-16 at 01:58 PM ----------

QuoteOriginally posted by clackers Quote
Unfortunately, you didn't shim it properly, Jerry. :-(
I've begun to hear that. I didn't realize shimming was necessary with Pentax focus screens. When I had swapped focus screens in a couple of Nikons a few years ago, it was a simple operation and everything worked immediately with no fine tuning or shimming needed. I also compared the two focus screens as I swapped them and realized the split prism focus screen was visibly thicker than the stock focus screen. I am beginning to think that my choice of the cheap screen might've sabotaged my efforts. I guess this is an example of you get what you pay for.

I might return to this project at a later date once I've done more research. What I don't know about shimming could fill a book. Still, despite the aggravation from last week, I think I learned a great deal as I tried to make my project work.
03-12-2016, 03:02 PM - 1 Like   #6
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QuoteOriginally posted by jerry7171 Quote
Sorry manual focus lenses, for the sake of my sanity, we can’t play together anymore.
Welcome to the forum, sorry to hear you say that, good luck with this new fangled autofocus malarky.
03-13-2016, 01:18 AM   #7
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QuoteOriginally posted by Kerrowdown Quote
Welcome to the forum, sorry to hear you say that, good luck with this new fangled autofocus malarky.
Never say never. I might try again in the future. Between the need to research shimming and seeing how new bifocals affect my vision I might yet get the confidence and knowledge to use manual focus lenses with more success. Maybe it will involve purchasing another split focus screen elsewhere too. Just the same, I'm having as much fun as a person can have with a camera.
03-13-2016, 01:26 AM   #8
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QuoteOriginally posted by jerry7171 Quote
I'm having as much fun as a person can have with a camera.
I'm a totally manual man who's wondering if I'll be "alligator wrestling" with the new K1's when they arrive.

03-13-2016, 03:03 AM   #9
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QuoteOriginally posted by jerry7171 Quote
. When I had swapped focus screens in a couple of Nikons a few years ago, it was a simple operation and everything worked immediately with no fine tuning or shimming needed.
My K-30 didn't need to be shimmed. You may have needed to shim other focus screens in your Nikons. Manufacturing variation and all. ☺
03-13-2016, 03:34 AM   #10
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QuoteOriginally posted by jerry7171 Quote
I previously owned a K-01 and enjoyed it, but I found that no matter how careful I was, I had trouble using my manual focus 50mm f:2 lens with it. Phase detection is a great step in aiding focus, but it never seemed to quite work for me.

I remembered using the old split prism focus screens on regular SLR cameras back in high school photography in the late 1980s. While it took a little longer for me to focus, I always had tack sharp focus on whatever I aimed at.

I set out on a misguided quest to replace the stock focus screen of my recently acquired K10D with a split prism focus screen. The main determinations were price and time. It came down to picking between eBay, focusingscreens.com or Amazon. I’d dealt with Fotodiox via Amazon before when I replaced the stock focusing screens in my old Nikons and they’d worked beautifully every time. The other advantage was the price of about $20 on Amazon versus $70 from focusingscreens.com. The last point for me was the wait time—I’m notorious for my lack of patience.

So off to Amazon I went and I order the screen. It arrived a few days later and I set to work.

After installing it, I found that instead of the sharp focus I’d expected when I lined everything up plus getting the green confirmation dot in the viewfinder, I found that I had a problem with front focus. Ok, I can deal with this. I printed out a cute little camera target and focusing ruler, glued and assembled it and carefully set everything up to begin the process of correcting the front focus issue.

Then I found that I had updated the K10D to the latest firmware and there wasn’t any debugging menu anymore. Whoops! So the next few hours were spent chasing down options on rolling back the firmware. I finally ran down the necessary files, installed them into the camera and tricked it into rolling back the firmware. All on a Mac no less! I then saved those buggers to my Dropbox in case I ever needed them again.

After several frustrating misses of accessing the elusive debugging option, I finally was able to tap in the sequence quickly enough to start it. Yes!

Then the next few days of agony began.

I could never seem to get the 50mm lens to work quite right. I’d finally think I had reached the sweet spot as I carefully dialed in the focusing adjustments, reaching the perfect focus, only to find that suddenly I couldn’t get any kind of sharp focus at infinity or that while it worked in the focusing tests, in the real world, it was still front focusing. I began to lose my grip on my sanity as I started over.

By this point, I started to look at my manual focus 50mm lens with a more jaundiced eye and began to question my desire to work with it. Sure the regular 35-80mm f:4-5.6 was adequate but it also had AUTO FOCUS and I was starting to think the old-fashioned way of doing things might not be so great anymore. But then another little voice would argue that the 50mm had a better light capture quality and could impart superior sharpness in my photos where I wanted it. So I trudged on.

I finally had a moment of brilliance and tried a few other lenses. Naturally they didn’t work quite right anymore either. Not at least until I zeroed out my adjustments in the debugging menu. Then they’d focus, but it took them more time than before and the focus was ever so slightly off. I tried using the split screen manual focus option but it was still the same problem.

I finally swapped the focusing screens again and tried everything out. With the stock focusing screen, my autofocus lenses hunted far less and gave me sharp results again. With the 50mm manual, I was back to a slightly softened, out of focus result no matter what aperture I tried, no matter that the focusing confirmation dot came on.

At this point, after resisting the urge to smash the old manual focus lens with a sledgehammer while speaking in tongues, I’ve begun to see the light and embrace autofocus lenses in spite of their higher prices. Sorry manual focus lenses, for the sake of my sanity, we can’t play together anymore.
Sorry to learn of these misadventures. I installed a split-screen in a K-20 specifically for use with legacy lens, and I lived happily ever after.
03-13-2016, 12:57 PM   #11
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QuoteOriginally posted by Kerrowdown Quote
I'm a totally manual man who's wondering if I'll be "alligator wrestling" with the new K1's when they arrive.
Please do keep everyone informed! If I could afford it, I'd have gotten a K1. It would be overkill for what I use photography for but it would be an awful lot of fun making such highly detailed photos for my hobby (photogrammetry). I think since it is a full frame camera that it could use a legacy split prism from a rangefinder Pentax? I see those float up on Craigslist and shopgoodwill.com frequently at prices so low that you essentially are just paying postage to take them off the sellers hands. I haven't done a search today, but I wonder if this is a topic already elsewhere?

---------- Post added 03-13-16 at 01:03 PM ----------

QuoteOriginally posted by clackers Quote
My K-30 didn't need to be shimmed. You may have needed to shim other focus screens in your Nikons. Manufacturing variation and all. ☺
Where did you order your focus screen from? Was it eBay or focusscreens.com? The particular example I ordered on the cheap from Amazon doesn't look like it was the right thickness and that makes me wonder if that was a factor in my lack of success? The stock screen was plainly thinner.

---------- Post added 03-13-16 at 01:09 PM ----------

QuoteOriginally posted by ivanvernon Quote
Sorry to learn of these misadventures. I installed a split-screen in a K-20 specifically for use with legacy lens, and I lived happily ever after.
If it weren't for bad luck, I don't think I'd have any luck at all! Ha! I strongly suspect my choice of a cheap screen via Amazon instead of the more expensive screen from focusscreens.com was the reason for my lack of success. Is that where you purchased yours? Or did you find yours elsewhere?
03-13-2016, 04:52 PM   #12
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In theory your replacement focusing screen should use the same shimming as the old one. But the reality is the level of accuracy needed is low since auto focus is not affected by the shimming. This is why the shimming might be off.
03-13-2016, 10:48 PM   #13
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QuoteOriginally posted by jerry7171 Quote
Please do keep everyone informed! If I could afford it, I'd have gotten a K1. It would be overkill for what I use photography for but it would be an awful lot of fun making such highly detailed photos for my hobby (photogrammetry). I think since it is a full frame camera that it could use a legacy split prism from a rangefinder Pentax? I see those float up on Craigslist and shopgoodwill.com frequently at prices so low that you essentially are just paying postage to take them off the sellers hands. I haven't done a search today, but I wonder if this is a topic already elsewhere?

---------- Post added 03-13-16 at 01:03 PM ----------


Where did you order your focus screen from? Was it eBay or focusscreens.com? The particular example I ordered on the cheap from Amazon doesn't look like it was the right thickness and that makes me wonder if that was a factor in my lack of success?
It's a Katzeye - no longer in business, I'm afraid.

It came with shims but the camera tech I paid to put it in said they weren't needed.

@Stevebrot knows which ones to try from focusingscreens.com, though.
03-14-2016, 10:23 AM - 1 Like   #14
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QuoteOriginally posted by clackers Quote
@Stevebrot knows which ones to try from focusingscreens.com, though.
I know a little what to avoid, that is all.

QuoteOriginally posted by jerry7171 Quote
Then I found that I had updated the K10D to the latest firmware and there wasn’t any debugging menu anymore. Whoops! So the next few hours were spent chasing down options on rolling back the firmware. I finally ran down the necessary files, installed them into the camera and tricked it into rolling back the firmware. All on a Mac no less! I then saved those buggers to my Dropbox in case I ever needed them again.

After several frustrating misses of accessing the elusive debugging option, I finally was able to tap in the sequence quickly enough to start it. Yes!
Focus adjust using debug only adjusts the auto-focus system. It does not affect the calibration of your new focus screen. The two systems are completely uncoupled. My suggestion would be to undo any debug mode changes you might have made. They are just "noise in the channel" in regard to your new screen.

QuoteOriginally posted by jerry7171 Quote
I finally swapped the focusing screens again and tried everything out. With the stock focusing screen, my autofocus lenses hunted far less and gave me sharp results again. With the 50mm manual, I was back to a slightly softened, out of focus result no matter what aperture I tried, no matter that the focusing confirmation dot came on.
While the confirmation dot gives an indication of correct focus, its results are always within the limitations of the AF system. As a result, work with a fast manual focus lens (maximum aperture wider than f/2.8) may be unsatisfactory if shooting at wider apertures. The reasons are complex, but it is enough to say that precision of the AF system is rather poor. Unfortunately, the same is true for manual focus using the stock focus screen due to low magnification and exaggerated depth of field (DOF).

The conventional solutions run like this:
  • First, make sure your eyepiece diopter is set properly to your eyes. Use the AF area printed lines as a guide. These should be in sharp focus when properly adjusted.
  • Use live view (not available on your K10D)
  • Viewfinder magnification may give enough of an edge to make the stock screen usable. At least that is the word from some users on this site. The Pentax 0-ME-53 is highly favored, but other magnifiers from eBay and elsewhere might also work (Pentax O-ME53 Magnifying Eyecup 30150 B&H Photo Video)
  • Aftermarket focus screen. The two types below are strongly favored:
    • Split/image or other focus aid. This type of screen may be familiar to users of film SLRs. One major caution is that the center split will affect accuracy of your camera's spot meter option.
    • Super Precision Matte (Canon-S). This type of screen is optimized for use with fast lenses and will darken considerably at f/4 and narrower. That being said, its ability to snap focus is pretty amazing.
If you decide on an aftermarket screen, you have a couple of options. You can buy a Nikon or Canon screen from B&H or elsewhere and cut it to size itself or get one already cut down from an eBay, Amazon, or Web merchant. I caution strongly against the first two. In the past we had the choice between two excellent Web-based makers, Katz Eye and focusingscreen.com.

Unfortunately Katz Eye went out of business last year. That leaves us with focusingscreen.com. Fortunately focusingscreen.com has a good selection and makes a quality product. In fact, their selection is broad enough that making a choice may be confusing. My recommendations from them are:
  • (Nikon) K3 Split-image/Microprism (LINK). The K-3 was made for use in Nikon the FM3A camera and is very similar to a Katz Eye screen in both appearance and performance. Its strengths are a split image that resists blackout down to almost f/11, competent ground glass ring and matte field, and a printed circular ring to assist in diopter adjustment.
  • (Canon) S-type Matte Field (LINK) As noted above, this screen excels when paired with a fast lens and when an unobstructed field is desirable. The trade off is that it dims significantly at narrower apertures such as are present with most kit zooms.
They offer a number of options for grid line or other etching. This is done using a laser and makes for a very clear bright line that is visible even in dim light. I would caution regarding ordering the grid lines due to potential for improper metering in dim light or narrower maximum apertures. At least that was my experience. One other caution regarding focusingscreen.com is that while they are very good at providing additional shims, they are very sticky about returns. Their policy is that if the inner packaging for the screen itself is breached, they probably will not accept a return. This makes sense given the nature of the product.

In regards to shimming...Yes, this addresses your original post. Focusing screen calibration is done placing thin shim(s) between the screen and the bottom face of the pentaprism. That being the case, you may have guessed that screen thickness may affect calibration and it does. The various aftermarket screens may or may not have the same thickness as your stock screen. Often times, using an aftermarket screen will not require any changes to the shims. That was the case with my K10D. Other times, that may not be the case. I had to change out the shims on my K-3.

How to adjust screen calibration:
  • Before attempting shim adjustment, be sure the screen is properly seated within its frame and recess
  • Add thickness for back focus
  • Subtract thickness for front focus
  • With live view both accuracy and direction to correct are fairly easy to determine
  • Without live view, it is a matter of trial and error using actual photos. This is one case where a slant focus device may be useful to at least provide an hint as to direction and amount of shim needed.
  • Focusingscreen.com provides decent instructions for installation and calibration, but getting to the most useful resource is not straightforward. This page is used for almost all Pentax dSLRs: --Pentax K5/K7/K10D/K20D/K30/K50/ISTD/K-S1/K-S2 Focusing Screen Installation Instruction-- At the bottom of the page are links to assist with calibration*
  • If you do need to adjust with shims, remember that the shims go between the screen and the bottom face of the pentaprism. I don't remember if the K10D has a separate retainer frame for its shims. If so, it will be between the screen and the bottom face of the pentaprism.

In regards to metering...The camera's meter system takes its readings off the focus screen. As a result changes to the apparent brightness or look of the screen may affect meter accuracy. These problems will exist regardless of whether you have a modern lens on the camera. The most common problem is with spot metering. With a split screen this is effectively disabled. The other is that the screen may be somewhat dimmer than the stock screen when used with slower lenses. Depending on the screen design, the effect may be severe. As mentioned above, laser etched grid lines may also fool the meter. My experience with the K-3 and S-type screen with etched AF-area lines was that of 1.5 - 2 stops under exposure in dim light or at f/4 maximum aperture.


I hope this covers everything


Steve

(...been using a Katz Eye screen for about eight years now...very happy...)

Last edited by stevebrot; 03-14-2016 at 10:35 AM.
03-14-2016, 09:59 PM   #15
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QuoteOriginally posted by stevebrot Quote
I know a little what to avoid, that is all.



Focus adjust using debug only adjusts the auto-focus system. It does not affect the calibration of your new focus screen. The two systems are completely uncoupled. My suggestion would be to undo any debug mode changes you might have made. They are just "noise in the channel" in regard to your new screen.



While the confirmation dot gives an indication of correct focus, its results are always within the limitations of the AF system. As a result, work with a fast manual focus lens (maximum aperture wider than f/2.8) may be unsatisfactory if shooting at wider apertures. The reasons are complex, but it is enough to say that precision of the AF system is rather poor. Unfortunately, the same is true for manual focus using the stock focus screen due to low magnification and exaggerated depth of field (DOF).

The conventional solutions run like this:
  • First, make sure your eyepiece diopter is set properly to your eyes. Use the AF area printed lines as a guide. These should be in sharp focus when properly adjusted.
  • Use live view (not available on your K10D)
  • Viewfinder magnification may give enough of an edge to make the stock screen usable. At least that is the word from some users on this site. The Pentax 0-ME-53 is highly favored, but other magnifiers from eBay and elsewhere might also work (Pentax O-ME53 Magnifying Eyecup 30150 B&H Photo Video)
  • Aftermarket focus screen. The two types below are strongly favored:
    • Split/image or other focus aid. This type of screen may be familiar to users of film SLRs. One major caution is that the center split will affect accuracy of your camera's spot meter option.
    • Super Precision Matte (Canon-S). This type of screen is optimized for use with fast lenses and will darken considerably at f/4 and narrower. That being said, its ability to snap focus is pretty amazing.
If you decide on an aftermarket screen, you have a couple of options. You can buy a Nikon or Canon screen from B&H or elsewhere and cut it to size itself or get one already cut down from an eBay, Amazon, or Web merchant. I caution strongly against the first two. In the past we had the choice between two excellent Web-based makers, Katz Eye and focusingscreen.com.

Unfortunately Katz Eye went out of business last year. That leaves us with focusingscreen.com. Fortunately focusingscreen.com has a good selection and makes a quality product. In fact, their selection is broad enough that making a choice may be confusing. My recommendations from them are:
  • (Nikon) K3 Split-image/Microprism (LINK). The K-3 was made for use in Nikon the FM3A camera and is very similar to a Katz Eye screen in both appearance and performance. Its strengths are a split image that resists blackout down to almost f/11, competent ground glass ring and matte field, and a printed circular ring to assist in diopter adjustment.
  • (Canon) S-type Matte Field (LINK) As noted above, this screen excels when paired with a fast lens and when an unobstructed field is desirable. The trade off is that it dims significantly at narrower apertures such as are present with most kit zooms.
They offer a number of options for grid line or other etching. This is done using a laser and makes for a very clear bright line that is visible even in dim light. I would caution regarding ordering the grid lines due to potential for improper metering in dim light or narrower maximum apertures. At least that was my experience. One other caution regarding focusingscreen.com is that while they are very good at providing additional shims, they are very sticky about returns. Their policy is that if the inner packaging for the screen itself is breached, they probably will not accept a return. This makes sense given the nature of the product.

In regards to shimming...Yes, this addresses your original post. Focusing screen calibration is done placing thin shim(s) between the screen and the bottom face of the pentaprism. That being the case, you may have guessed that screen thickness may affect calibration and it does. The various aftermarket screens may or may not have the same thickness as your stock screen. Often times, using an aftermarket screen will not require any changes to the shims. That was the case with my K10D. Other times, that may not be the case. I had to change out the shims on my K-3.

How to adjust screen calibration:
  • Before attempting shim adjustment, be sure the screen is properly seated within its frame and recess
  • Add thickness for back focus
  • Subtract thickness for front focus
  • With live view both accuracy and direction to correct are fairly easy to determine
  • Without live view, it is a matter of trial and error using actual photos. This is one case where a slant focus device may be useful to at least provide an hint as to direction and amount of shim needed.
  • Focusingscreen.com provides decent instructions for installation and calibration, but getting to the most useful resource is not straightforward. This page is used for almost all Pentax dSLRs: --Pentax K5/K7/K10D/K20D/K30/K50/ISTD/K-S1/K-S2 Focusing Screen Installation Instruction-- At the bottom of the page are links to assist with calibration*
  • If you do need to adjust with shims, remember that the shims go between the screen and the bottom face of the pentaprism. I don't remember if the K10D has a separate retainer frame for its shims. If so, it will be between the screen and the bottom face of the pentaprism.

In regards to metering...The camera's meter system takes its readings off the focus screen. As a result changes to the apparent brightness or look of the screen may affect meter accuracy. These problems will exist regardless of whether you have a modern lens on the camera. The most common problem is with spot metering. With a split screen this is effectively disabled. The other is that the screen may be somewhat dimmer than the stock screen when used with slower lenses. Depending on the screen design, the effect may be severe. As mentioned above, laser etched grid lines may also fool the meter. My experience with the K-3 and S-type screen with etched AF-area lines was that of 1.5 - 2 stops under exposure in dim light or at f/4 maximum aperture.


I hope this covers everything


Steve

(...been using a Katz Eye screen for about eight years now...very happy...)
Thanks for the in-depth explanation Steve. I really appreciate this! I can't wait to try again in another month or two.
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