[stevebrot]

On a K-3 as well? It has been a while since I pulled my screen.

Yep.


Steve

[John Shriver]

So I just retested with a more rigorous approach. Printed the Siemens Star from Wikipedia. Folded it in half and set it vertically. Put a sloped ruler next to it. Focused by eye on the star, and then checked the ruler with Live View. More or less dead on, or maybe focused 1mm behind the mark at 0.5 meters. I doubt I can do any better with shims in 0.1mm thickness increments.

[BigMackCam]

So I just retested with a more rigorous approach. Printed the Siemens Star from Wikipedia. Folded it in half and set it vertically. Put a sloped ruler next to it. Focused by eye on the star, and then checked the ruler with Live View. More or less dead on, or maybe focused 1mm behind the mark at 0.5 meters. I doubt I can do any better with shims in 0.1mm thickness increments.

I'd say that's an excellent result, John. It would be difficult to get better accuracy with a third party screen.

[tonezime]

I doubt I can do any better with shims in 0.1mm thickness increments.

I wonder if focusingscreen.com would be able to do anything useful with this feedback (e.g. provide an 0.05mm shim) or if they're at the limit of what they can provide already.

Thanks for sharing all this information, it's very helpful.

[UncleVanya]

So I just retested with a more rigorous approach. Printed the Siemens Star from Wikipedia. Folded it in half and set it vertically. Put a sloped ruler next to it. Focused by eye on the star, and then checked the ruler with Live View. More or less dead on, or maybe focused 1mm behind the mark at 0.5 meters. I doubt I can do any better with shims in 0.1mm thickness increments.

What focal length lens were you using? There is a rule of thumb for what distance to calibrate at based on focal length. 0.5m could be OK - or it could be too close.

[John Shriver]

Pentax-A 50mm f/1.2 lens. Figured it had the shallowest DOF of anything I have.

[UncleVanya]

Pentax-A 50mm f/1.2 lens. Figured it had the shallowest DOF of anything I have.

One of the test systems with a 150-250mm target gives a 2.5M distance. LensAlign suggests 25x the focal length at a minimum. So about 4' for that one. Your target size may be smaller and require closer but generally a bit longer is preferred by these systems. I don't know if that helps you any.

[John Shriver]

So I went on vacation with the K-1 with the "S" screen. I found I was having to change the exposure compensation for each lens. Quite an annoyance!

Tempts me to put back the stock screen, and admits that I may just have to use Live View with focus peaking to use manual focus lenses like Pentax-A 50/1.2 and Komura 100/1.8. Heck, I even had some focusing challenges with the Pentax-A 16/2.8 fisheye, and it has gobs of DOF.

I really miss manual focus, and wish it could be done well with the K-1. (It's a joy on the Pentax LX.) Of course, maybe I wasn't all that accurate with it on my film cameras, but couldn't tell when shooting on film. With the power of pixel peeping via a 36 megapixel sensor, you get fussy...

[stevebrot]

So I went on vacation with the K-1 with the "S" screen. I found I was having to change the exposure compensation for each lens. Quite an annoyance!

Are you saying this for stop-down metering only or for open-aperture metering too?

Heck, I even had some focusing challenges with the Pentax-A 16/2.8 fisheye, and it has gobs of DOF.

Unfortunately fisheye lenses have the same DOF as rectilinear lenses of the same focal length and may be noticeably thin at moderate distances. Everything is too teeny to assess focus, but it can still be out a fair amount and that fair amount is readily evident at full resolution. A split image is sensitive enough with my Zenitar 16/2.8 as is live view...the matte field, not so much so.

Sorry this solution turned out to be a disappointment.


Steve

[John Shriver]

This was all open-aperture metering, all the lenses were Pentax-A or Pentax-FA.

But this whole non-linearity of screen brightness with f-stop is probably also why folks have problems with "green button" stop-down metering.

[stevebrot]

But this whole non-linearity of screen brightness with f-stop is probably also why folks have problems with "green button" stop-down metering.

That is a part of it.


Steve

[pschlute]

But this whole non-linearity of screen brightness with f-stop is probably also why folks have problems with "green button" stop-down metering.

You should have tried stop-down metering with old lenses on the K-10 !!

[John Shriver]

Finally gave up a month ago and put the original screen back in. If I'm doing tough MF, I'll just have to use live view. The exposure hassles are just too much.

[stevebrot]

Finally gave up a month ago and put the original screen back in. If I'm doing tough MF, I'll just have to use live view. The exposure hassles are just too much.

Sorry to read this, though I understand. Are you planning on writing a review of the screen?


Steve

[felixkh]

I have the K-1 F6-L Focusing Screen (Nikon) from Focusingscreen.com and focusing is great. I did not have to change the shims but needed to add little stickers to the sides of the screen to align to the centre.

Focusing Screen