Topic: matte screen or fresnel in 35 mm SLR?

[imagesfrugales]

Hi folks,

the screens from the mid 70s to mid 80s on almost all mf 35 mm SLR were the brightest ever, before autofocus came and had eaten up all the good properties. None of the latter came even near to the screen image quality of a humble Minolta X-300. But these ultra bright screens seem to have a big disadvantage that they share with the recent AF screens: the dof is displayed much bigger than it is later in the image. I heard that only real oldschool matte screens without any "tricks" can show the real depth of field, be it wide open or stopped down.

This is quite important for me because I want to shoot much more with a diy single element lens with a very narrow dof and it's extremely difficult for me to predict the wanted effect. Which M42 SLR would be suitable, I only know of the early Zenits. f.e. the Zenit B.

Here's an example with the lens:

the last sunflowers by imagesfrugales, on Flickr

[Francois]

Well, most of the screens have had a fresnel lend for a long time, especially 35mm.
But I do have an Argus STL 1000 which has a regular non-fresnel screen with focus spot in the center. It's pretty massive and heavy.

My Praktica L has a pretty coarse fresnel, so I think that is better avoided.
I also have a Mamiya MSX 1000 which has a very smooth fresnel.

You'll probably get a lot of information here
http://camera-wiki.org/wiki/M42

[jojonas~]

A x-300 minolta should work fine with a lensless adapter. Gotta love that short flange distance of the old minolta mount

[imagesfrugales]

I have several X-300, Jonas, great cams and cheap. I renewed the odd capacitor in each one. They have the biggest and brightest screens available, but that's the problem here. I'm looking for a M42 SLR with an old fashioned ground glass screen, because the bright ones don't show the real dof. This is an almost unknown fact. And the X-300 has no stop down lever ;-)

[Ezzie]

What about the Fujicas? ST801 for instance? Bright, micro prism and split image focusing.

[imagesfrugales]

Mh, how can I say it? I do not want a bright screen with bells and whistles. I have about  10 SLR bodies with the brightest screens ever made on this planet. They do not show the real depth of field as it will be later in the real image you hold in your hands. This fact is rarely known.

I do want a SLR body with an oldschool ground glass without microprisms and split image. No fresnel, but simple ground glass, nothing else. I want to use it for proper focusing and prediction with an extremely narrow depth of field.

A Zenit B f.e. would provide such a screen

http://camerapedia.wikia.com/wiki/Zenit_B

but I thought there should be some other models exept the heavy and ugly Zenits. See how difficult it is to get the proper info, the camerapedia artical contradicts himself. First it says: "There were also no focusing aids apart from the plain ground-glass screen." And some lines later: "Focusing: Fresnel matte glass screen". There is quite a difference between a fresnel screen and a ground glass screen.

[imagesfrugales]

sorry, double post

[mcduff]

I cannot help with your quest but thanks for explaining what I have internally realized but never articulated - the discrepancy between what I see in the VF and on the neg. So there are no replaceable screen M42 SLRs? I am pretty sure the OMs could use a matt screen but that will not help unless u got an adapter.

[tkmedia]

The Minolta screens were so good that they licensed them to other manufacturers like hassy, fuji!

[Francois]

I think I have your solution!
I was looking in an old Nikon book and discovered that for an F-2 type camera you can get the following screens:
Type C: fine ground matte with 4mm clear spot and cross hair
Type D: all-matte fine ground surface

These were available for the F2, F2A Photomic and F2AS Photomic.

I'm pretty sure other makers had them for some models. This is an option that was only available on professional gear... though I don't think it matters much now.

These were suggested for micrography... if that helps.

[Flippy]

For plain matte screens and m42 - probably the easiest bet is one of the later Exas. They all have interchangeable screens, and the plain ground glass screen is probably the most common.  You can switch to a microprism or fresnel if you want to at any time.

The Exaktas take the same screens, but do not have an M42 mount - although one from an Exa can be swapped in easily. 

The Edixa SLRs continued without fresnel screens to the end, although they began to use a split image prism in the center from the 1960s. The better models had interchangeable screens.

Just about every 35mm SLR adopted fresnel screens by the early 60s.

I want to add a couple things: even a ground glass will not give you a 100% accurate display of depth of field, as the coarseness of the grind will change this effect in the viewfinder. Second: a split prism is really nice for ultra precise focusing, although I use plain ground glass a lot, my favorite type is the ground glass with a split image spot. This gives quick, precise focusing, and a good idea of depth of field and lens effects. 

[jojonas~]

ah, an all matte screen? sorry for the misunderstanding!

okay.. m42 and no focus help. just matte screen? this might not be an easy to use camera but smaller than a zenit b at least... have you looked up the contax s?
the prism is just filed on the bottom part. I read about it here (swedish) http://www.fotosidan.se/blogs/straightphotography/straight-2116-contax-s-och-den.htm

more info on the camera and others from the same era here: http://www.earlyphotography.co.uk/site/entry_C285.html

[imagesfrugales]

Oh yes, the Contax S. A beautiful camera and anchestor of all Prakticas. There must be some Prakticas with ground glass only but I have no overview about the many many models.

[mcduff]

OK now if I see a Matt screen for my OM stuff for sale I am going to buy one just to I can see my DOF for once. (I can see why it will not be a good all around focusing aid but you have piqued my nerd interest!)

[imagesfrugales]

.... but you have piqued my nerd interest!

hehe, don't blame me for extended gas :-D

PS: thank you very much, Flippy, for the further infos, they are highly appreciated.

[Flippy]

Chronologically speaking, the KW praktiflex is more the ancestor of the Contax, than the Contax is the ancestor of the Prakticas.

I would not recommend the Contax though, aside from most not being in working order these days, the viewfinder is not very good compared to Exaktas/Exas or even Edixas really - it's dim and small, and often blurry/discolored from deterioration of the silvering on the prisms.

I think all the Prakticas used a ground glass up until the Nova series. An FX3 can be a fun camera to use.

[imagesfrugales]

OK, FX3 is an option, maybe also the Praktica IV?

[Flippy]

The original IV has a plain screen, but the later variants use a split image.

I think the upside with the FX3 is that the magnifier on the WLF will make precision focusing easier than it will be through a pentaprism (lower magnification) on the IV. But if eye level viewing is important, than the IV may be a better choice.

[steve_pounder]

I am confused by this thread. The reason why modern cameras do not normally show the correct depth of field when viewing is because the lens is wide open except during the time that the shutter is firing, even when the lens itself is set to a high aperture. The Zenit B did not have the ability to open up the aperture between shots, hence  the depth of field seen in the viewfinder was always what you got on the film. It has nothing to do with the focusing screen, which is just a piece of glass.

To see the depth of field at the taking aperture, use a camera or lens with a depth of field preview facility.

Or have I got this completely wrong?

[mcduff]

I have been reading about the dozen plus screens avail for the OM. It is interesting in that there are a few all-matte screens but one brags about being an extra fine matte finish that was designed for astrophotogtaphy and extreme close up work (funny, ligjt years or inches away). I  presume that one may be fun for me to find and play with if I want to have a more accurate experience of DOF.

[Francois]

This is not really surprising in a way. I used to have a 500mm mirror that was giving me hell. It caused the fresnel screen to go dark at odd angles depending how I placed my eye...

[imagesfrugales]

"Or have I got this completely wrong?"

Yes. Sorry.

The fact is quite unknown that bright fresnel screens show a wrong (always bigger) depth of field compared to the final image. No matter if stopped down or not. Make a shot f.e. with a 1.4/50 lens wide open, focus at maybe 1 meter, compare the print with the "live" image on the screen. Only DSLR with live view will show the real dof. Every screen will show a bigger dof, the simple ground glass screens are closest to the final image, the bright screens are the worst in this regard.

Next, with slow telephoto lenses or other slow lenses the split image focus aid is completely useless, the microprisms are also often misleading, plain ground glass was always recommended by the manufacturers for telephoto, at least when they were offering different exchangeable screens. Of course they never said: don't trust our bright screens.

The first pictures I made with this homemade meniscus lens were unusable because the dof was shown much bigger on the camera screen, I was really shocked, see below. I added a smaller aperture made from cardbord and the images were usable. Getting a realitic impression of the final image still is delicate. A better, plain ground glass screen would surely help.

[Francois]

Have you tried replacing the fresnel with a home made screen made from the cover of a CD case that has been sanded?
If the thickness is right, it just might work.

[imagesfrugales]

Have you tried replacing the fresnel with a home made screen made from the cover of a CD case that has been sanded?

No, although I tinker a lot I'm not brave enough. I guess the focus has to be adjusted then very carefully. With a 35mm SLR it should be much more difficult as with a 6x9 folder and a simple infinity adjustment. Maybe I should get a working Zenit B with the regular plain ground glass. A Nikon F2 with exchangeable screens would be nice of course, but it's still quite expensive and I don't have a single Nikon lens, but some really fine M42, Canon-FD and Minolta-SR lenses. And I can't change the system because all those fine lenses would be absolutely unaffordable for me from Nikon.

[Flippy]

I have a feeling from the images you are posting it's not simply a matter of judging depth of field, but you're not accurately seeing the effect of the lens - have you taken any pictures which show an even plane of focus at all? Because what I see looks like what happens when you pull the aperture out of an old box camera lens and you get a soft focus effect. That is it looks like you won't get a sharp area regardless of what screen you use to focus,  the lens is just incapable of providing a sharp area unless you fit it with some sort of aperture.

[imagesfrugales]

Yes, it is a meniscus as in simple box cameras but with a much too big aperture producing huge amounts of aberations. That is what the lens was made for. No, the images have a decent sharp center. But judging the aberations is almost impossible with a regular fresnel screen, because they show a much too deep dof. So the blurred corners appear much to sharp on the fresnel screens. Thank you.

[imagesfrugales]

PS: the aforementioned characteristic is intrinsic for all fresnel screens with all lenses, also the "good" ones.

PS2: the lens above can be focused rather precisely by moving the element forth and back, range is from about 50cm to oo