bright viewfinder is not necessarily best

[RobC]

Some years ago I put a bosscreen on my technikardan. It made a big difference to the viewfinder brightness but I've always found it difficult to focus exactly.
I just put back the original Linhof ground glass and using a 45 reflex viewer in dim light just after sunset, I was able to focus really accurately even though it is far less bright than the bosscreen.
The crop is from a notice board to the left of the arched church door and is at 100% of scan resolutoin which was done at 3200dpi unsharpened. On the neg with a 6x loupe, I can read most of what is on that notice board so I'm really pleased I put the old GG back. It just seems to snap into focus unlike the bosscreen.
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[darinwc]

why was the boss screen harder to focus? was it just not sharp or was there a 'hot spot'

 

[RobC]

It's because the granularity in the linhof gg is either in focus or not. There seems to be a point with the linhof glass that it just pops into focus which is obvious. With the bosscreen a little either side of focus is difficult to detect, especially in dim light. I seemed to get more images slightly off focus with the bosscreen. It could just be me but I'm pleased with going back to the linhof gg. I should have done it long ago.

 

[gbenaim]

I had a similar experience w an Beattie Intenscreen and then a regular satin snow gg. There was probably a 2 stop difference, but the satin snow was much sharper.

 

[ic-racer]

I have had this same experience with a Intenscreen. The brighter a screen is made, the closer it gets to an 'impossible-to-focus' aerial image.

I remember using a Beaulieu movie camera in which the focusing screen could flip out of the way, so you could have the best of both worlds

 

[Chris Breitenstein]

I think that has something to do with the use of a Fresnel; It creates a distinct spiral pattern that is almost impossible to get a sharp focus through. I can see how that would definitely be a problem if you are making enlargements.

yours;

 

[Steve Hamley]

Same experience with a Maxwell versus Ebony. I like the Ebony better because it "snaps" into focus. Granted the Maxwell is about 1/2 to a stop brighter, but it does not "snap" into focus. I think a lot of people want a "TV screen" with no granularity, but don't realize the effect granularity has on determining accurate focus.

That said, a Maxwell for a wide angle may likely be a good thing.

Cheers,

Steve