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01-14-2016, 02:42 PM   #1
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Manual Focus Tips

I've used to have a Zenith with manual focus in the USSR, and it had split screen. K-3II seems to have nothing special for MF, right? For manual lenses like Voigtlander Nokton 58mm, what do folks do to improve MF accuracy?

A+

01-14-2016, 02:52 PM   #2
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Until recently, Katzeye was a popular solution, but their last production run was November 2015.
01-14-2016, 02:58 PM   #3
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Catch in focus is nice. Switch the camera to AF, hold down the shutter button and focus close to the area and then fine focus. It will fire for you. Burst shooting helps too. It works for all the K mount lenses, although not very good for M42 lenses since they don't have a metal connection right on top of the connections in the mount.
01-14-2016, 03:03 PM   #4
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There is also a "focus indicator" in the viewfinder. And if you can afford LV (or have to use it) then focus peaking (for dynamic scenes) and 10x magnification (for static scenes - in my opinion best accuracy).

01-14-2016, 04:41 PM   #5
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+1 live view with magnification to give best accuracy and corroborate your OVF efforts.

Your main options to add to the OVF are
1. change the focus screen as mentioned. Check out some of the numerous threads like this recent one:
https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/311710-manual-fo...ng-screen.html
2. A magnifier. The O-ME53 is a good option, but for me a Tenpa 1.36x works better see my review. Lives on my K5.

Viewfinders and Screens - Pentax Camera Accessory Review Database

Last edited by marcusBMG; 01-15-2016 at 05:03 PM.
01-14-2016, 07:20 PM - 3 Likes   #6
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QuoteOriginally posted by braver Quote
For manual lenses like Voigtlander Nokton 58mm, what do folks do to improve MF accuracy?
We can start by complaining to Ricoh/Pentax regarding poor selection of focus screens. Here is the executive summary of the current state of manual focus on Pentax dSLRs:
  • The stock focus screen has poor precision. In technical terms, its focus sensitivity is about f/4 meaning that the ability to attain fine focus with an f/2 lens is the same as with an f/4 lens. This is due to exaggerated DOF that is never narrower than that present at f/4.*
  • The focus confirmation system also has a focus sensitivity of f/2.8 on your K-3II, but only for the center column of AF points. The other points are f/5.6.
  • Catch-in-focus (CIF) has the same limitations as focus confirm.
  • None of the above are adequate for fine focus with an f/2 or faster lens, particularly at longer focal lengths
  • The conventional solutions are to either use magnified live view (gold standard) and/or replace the stock screen with something having higher focus sensitivity and/or use a viewfinder magnifier
  • I have not used a viewfinder magnifier, but some users on this site report good results
  • There are two screen variants that are popular by users on this site:
    • Canon S-type (high performance matte field)
    • Split-image/microprism with matte field
  • The S-type screen works real well with faster lenses (focus sensitivity of about between f/1.2 and f/1.4) and not so well with slower glass (maximum aperture below about f/3.5). The screen gets very dark very quickly. There may also be problems with metering with some models.**
  • The split-image types also work very well with focus sensitivity in excess of f/1.2, but depend on the presence of a vertical line at the intended plane of focus. The microprism ring on most versions may be used instead, but has fairly limited focus sensitivity (f/2.8 - f/3.5 depending on screen). The better split-image screens have a matte field that rivals the S-type.
  • Options for the Canon S-type include:
    • Cutting your own from a FF Canon screen. These may be purchased for reasonable money from B&H and other online vendors.
    • Buying pre-cut from an Internet vendor. Users on this site have had good luck with screens from focusingscreen.com and that is my recommendation over the eBay vendors. When buying pre-cut, it is usually possible to order with various inscribed grids or other markings.
  • Options for split image are similar to those for the S-type. The Nikon K3 screen is favored for DIY and also pre-cut from focusingscreen.com. Focusingscreen.com has example views for the screens that they sell. If Katz Eye were still in business, I would give their screen (split-image similar to the Nikon K3) a strong recommendation, but alas, they are gone
Well, there you go. My personal testimony is that I was getting ho-hum results from my manual focus attempts on my K10D back in 2007 until I got a Katz Eye. Making the switch made all the difference. Now that I have the K-3, having a good screen is all the more important and I would not be without it.

Having made a strong case for an aftermarket screen, here are the cautions:
  • Neither the Canon S-type or split-image screens will be as bright as the Pentax stock screen with most lenses
  • Adding a center focus aid (split image or microprism) will adversely affect spot metering. This is a historic problem dating back to the earliest spot-metered SLRs. When I move to a split screen, I kissed spot metering goodbye. As always, YYMV so it may be worth a try.
  • Metering...Most screens do not have a huge impact on meter performance, though the potential is definitely there, particularly if there is an split-image blackout (see below)
  • Prism blackout (half or all of the prism goes dark) is a characteristic with all split-image screens at narrower apertures. The point of black-out depends on the design of the screen and below that point the split is not usable. Resistance to blackout is one of the strong points of the Nikon K3 screen and also of the late and lamented Katz Eye. Both are generally usable down to between f/8 and f/11.
  • Calibration...You notice I left this one until last. The good news is that a well-calibrated screen of decent quality will outperform the best PDAF systems currently available. The bad news is that most aftermarket screens will only be properly calibrated using the shims inserted when the camera was made if they are the same thickness as the stock screen. Unfortunately, most are not.
    • Calibration is not hard, just tedious and made more so if you don't have access to decent shims
    • Shims...yes, I said shims. They fit between the focus screen and the bottom of the pentaprism. Too thick and you have front focus. Too thin and you have back focus. (I think...)
    • Some vendors include plastic shims (e.g. focusingscreen.com), but they tend to be flimsy and it is often not clear which ones to use
    • Some users on this site have shimmed using thin strips of paper
    • Ricoh/Pentax will not sell official shims to other than repair shops
    • Katz Eye (RIP) had access to and would sell shims on their Web site, but alas, no more ***

Well there you go!


Steve


* The reason is complex, but has to do with screen optimization to offset the light lost to service the AF system (the main mirror is half-silvered).

** I had problems on the K-3 with an S-type screen that I bought from focusingscreen.com. I added brightline laser etching (AF zones) and the had severe problems with underexposure. As always, YYMV, but it should be noted that they do not accept returns for that sort of thing.

*** Forum rules stipulate that we are not supposed to sell outside the marketplace, but I know what happened to Katz Eye's stock of shims...

Last edited by stevebrot; 01-14-2016 at 07:26 PM.
01-15-2016, 04:44 PM   #7
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This is not a very easy state of affairs! I'm not feeling like messing with my camera to install screens, would rather have it done in a clean room with proper equipment. Should be a factory-service option... Also am not willing to sacrifice brightness. Ideally would be an add-on solution I could add with manual lenses... Very strange that a DSLR with optical path and legacy lenses does not provide an easy way to do MF these days. Wonder if the FF will be better.

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01-15-2016, 04:53 PM   #8
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Get yourself an O-ME53 eyepiece magnifier and go take photos. For me it was quite an improvement, especially on the small and dim K100D viewfinder. Practice! Over time, you *will* get better as you become accustomed to manual focus. And, as others have said, live-view and focus peaking are very effective.


Last edited by paulh; 01-15-2016 at 04:58 PM.
01-15-2016, 04:55 PM   #9
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QuoteOriginally posted by braver Quote
This is not a very easy state of affairs! I'm not feeling like messing with my camera to install screens, would rather have it done in a clean room with proper equipment. Should be a factory-service option... Also am not willing to sacrifice brightness. Ideally would be an add-on solution I could add with manual lenses... Very strange that a DSLR with optical path and legacy lenses does not provide an easy way to do MF these days. Wonder if the FF will be better.

A+
I don't think the FF will be any better in this regard. I may be wrong.

Pentax does not produce a split prism focusing screen. As Steve already mentioned, those from "focusingscreens.com" are the best currently available. I have one I fitted to my K3 and it's excellent - really excellent.

Any camera, whether Pentax, Nikon, Canon etc. would require the same work to fit a new focusing screen - it's not a Pentax-specific thing. If you're not happy fitting one yourself, the better local camera shops would be able to do this for you, for a fee. But, I had no problems fitting mine. I was a little anxious, but I needn't have been.

I would also recommend the O-ME53 magnifying eye-cup for your camera. This slips on in place of the existing eye-cup and provides a bit more magnification through the optical viewfinder. It's more than good enough to allow me to focus my 50mm manual lenses and some of my 35's even without a split prism focusing screen. This might be your best first step.
01-18-2016, 08:10 AM   #10
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There are the Bresson focusing screens Bresson FS-45DS Split Image Focusing Screen reviews - Pentax Camera Accessory Review Database
I have one in K-3

This is totally belief that spot AF and metering go in between the splits. As I'm getting unchanged spot focus and metering.
Sure that is ugly to watch through and is darker than original lens. Serves me well with Soviet glass and gives peace of mind when using modern AF lenses.
01-18-2016, 01:40 PM   #11
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QuoteOriginally posted by braver Quote
I've used to have a Zenith with manual focus in the USSR, and it had split screen. K-3II seems to have nothing special for MF, right? For manual lenses like Voigtlander Nokton 58mm, what do folks do to improve MF accuracy?
mirrorless with a good evf is the most accurate, by far, but live view in the lcd also works, because both of those options have magnification capability.
01-18-2016, 02:23 PM   #12
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Yeah, all the above.
If you have lots of light, the Pentax viewfinders work pretty well for MF. Otherwise it's tough. I had a split-focus screen in my old K10 but didn't in the K5. Still, out in the field I'd drop to MF a lot with the K5 to get shots. The placement of the focus switch was convenient for that. I am considering adding one to my K3II if they don't screw up metering. I agree it would be a great option for a limited edition camera or B&H or someone to do this as a service upon purchase.
01-19-2016, 01:15 AM - 1 Like   #13
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If your eyesight's not the best, it's much easier to judge when two halves of a line coincide than look at pixels and decide if they're sharp enough. Split prism focusing can be very quick, no umming and ahhing, albeit it's for people who focus and recompose.
01-20-2016, 01:47 PM   #14
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So I'm playing with Voigtlander Nokton 58mm now, and it turns out this is not too bad as the camera is beeping when focus is achieved, which looks at the right time in focusing. However I have two reservations:

-- it asks to enter the focusing distance, and the nearest value is 55mm. K-3II seems to only offer a menu there, so I can't enter 58mm.
-- the focusing and beeping seems incessant when the focus mode switch is in AF position. E.g. if the last focus was on infinity, everything at infinity seems to cause the focus confirmation blink and beep. Turning the switch to MF seems to stop this. Probably the effect of AF-A, so AF tries to confirm focus continuously? Is there any recommendation on keeping focus mode AF or MF for confirmaion?

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01-20-2016, 03:57 PM - 1 Like   #15
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QuoteOriginally posted by clackers Quote
it's much easier to judge when two halves of a line coincide
This is one of the most powerful feature of human eyesight. Normally human can detect 1 arc minute difference. But when line makes sudden bump like one pixel shifts one pixel horizontally in one pixel wide vertical line. It can be detected even if it is less than arc minute. And that makes split screen so useful.
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