Nikon F2 Focus screen issue.

M

mlyonrubio

Newbie
Local time
2:11 AM
Joined
Sep 13, 2017
Messages
1
Hello
Im new to the forum and I've been dealing with an issue regarding my F2 focus screen.
For the F2, Nikon made several models of focusing screens.

I recently lost my focus screen. When I went to the camera shop (in Paris) to buy a new one they only had de G4 model.
As you can see below, taken from mir.com I found out the G4 was specially made for 300mm lens.

I own a 50mm lens and my question is if by using the G4 focus screen with my lens, will it make my photos be out of focus?

Thanks!

Type G (G1, G2, G3, G4)
Nikon description: Clear Fresnel field with extra-bright 12mm-diameter microprism focussing spot for use in poor light. Four models correspond to lenses with different focal lengths:

[​IMG]
G1 for fisheye
G2 for wideangles
G3 for 50f/1.2 and 300f/2.8
G4 for 300f/2.8
 
No, focus has nothing to do with focus screen variants, but seeing the image/DOF might be a problem. The G focus screens are specialty screens that work best with the listed lenses. I don't have a G4 but my guess is that it might have unexpected issues with "wrong" lenses. I do have a G3 and it works beautifully with my 50mm f/1.2, but it blacks out very easily in the center spot with slow lenses.

Instead of relying on local shops for decades-old accessories, try eBay. I wanted to try different focus screens and I bought about a dozen various types for a few dollars a piece.
 
"No, focus has nothing to do with focus screen variants" - this is incorrect, in fact it has, you can verify this by checking the focus on a chart and changing the screens, and this is also one of the reasons for making various screens and "matching" them to specific lenses. It has to do with the angle, at which the rays hit the screen, and also with the maximum aperture of the lens. There is good news though - you can also use screens from Nikon F3 on F2, by flipping the F3 screen upside down. Just look for one of the mainstream screens.
 
Why would the focus change? If the screens in question are not matched to the lens, I understand microprism blackout and such can happen, but if the focus is off it seems like it is a defective screen. I don't have any really oddball screens, like the ones for very long telephotos, so I have no way of testing really wacky combinations. I have used A, B, D, E, H, G, J, and K screens interchangeably with various lenses and never seen such a phenomenon.

My favorite screens for all types of photography are the J screens or similar microprism spot screens. Can't stand the pseudo-RF split-image screens, they drive me nuts.
 
Corran, As stated above, having a lens that actually focuses precisely on an SLR, is in fact, an exception. Convince yourself: place your camera on a tripod and shoot a target chart at 45% from 1 meter or so, and then observe the results with various lenses and screens. It has to do with the way the screen interacts with the angle of rays from lens. You will notice, that the differences get smaller as the focal length becomes longer.
 
I'm afraid my ability to focus wide angles through a squinty viewfinder is suspect, so that would be nothing more than a sobering reminder of such. Perhaps instead you can provide a link to someone else's test and perhaps more explanation about how the angle of rays changes the focus on a wide angle, thanks. As it stands I have never seen any problems in focus among my focus screens and normal lenses. Wide angles haven't seemed to be a problem either but larger apparent DOF could be the reason.
 
Corran said:
Why would the focus change? If the screens in question are not matched to the lens, I understand microprism blackout and such can happen, but if the focus is off it seems like it is a defective screen.
Click to expand...

Split prisms and microprisms ease focusing by selecting the edge rays of the lens, thus creating a wide focus base. But as a direct consequence, you focus on the worst possible zone on any basic lens type. If the lens does not have a perfectly flat field (very few do) or has the edges moustache-corrected to return back into the main plane of focus (a common trick of SLR lens manufacturers), the prism focus will inevitably be off. Hence the rather puzzling compatibility tables issued by Nikon - both aperture compatibility and the best possible focus location have to be taken into account when picking a screen to match a lens.
 
mlyonrubio, you can also use the Nikon F3 screens. Just file down the small ledge -- I have done this before and it's a very simple procedure. I find the B screen the best general screen.
 
mfogiel said:
"No, focus has nothing to do with focus screen variants" - this is incorrect, in fact it has, you can verify this by checking the focus on a chart and changing the screens, and this is also one of the reasons for making various screens and "matching" them to specific lenses. It has to do with the angle, at which the rays hit the screen, and also with the maximum aperture of the lens.
Click to expand...

It is a bit more complex than that - optical focusing aids (split and microprisms) have to account for aperture, exit pupil and curvature of field. The screen plane itself must invariably be in the same position as the film.

There is good news though - you can also use screens from Nikon F3 on F2, by flipping the F3 screen upside down. Just look for one of the mainstream screens.
Click to expand...

Not upside down - but that is self evident as it won't fit that way. Front to back will often work. If the fit is too tight, you must file off a bit of the F3 registration tab, or the screen won't sit flat in the proper position.
 
Can not flip upside down. Screens are actually two parts, the focus aid on the bottom piece and glass on the top with a "hill' on it facing up. The two are held together with tape around the edges. Then they are placed in the frame.

To take them apart, you need very small screwdrivers, good tweezers to hold the tiny screws when reassembling.

Flipping will place the actual focus screen way out of position.
 
F3 screens work fine in F & F2 bodies if you file off the tab on the F3 screen. Personally, when I did this (I did a number of such "conversions") I would always disassemble the screen before filing so that I could properly clean the frame and not risk getting filings onto the screen itself or between it and the condenser lens (these are not always "sealed" with tape).

The optical elements of most of the common versions of the early F3 screens will actually file inside of an F/F2 screen frame. The later "dot" (brighter) F3 screens will not fit properly into F/F2 screen frames. Also, the G and H series, and a few others, need their own special frames and can't be swapped into other frames.
 
As per recommendation of Brian Sweeney I went to an A screen and an E screen. They are great. I got rid of the other screens I had.
 
Dwig said:
The later "dot" (brighter) F3 screens will not fit properly into F/F2 screen frames.
Click to expand...

This is not true. As any F2 and F3 screens they won't fit in the first series of F screen frames only. This is the same for Nikon F4 focusing screens (which are identical to the "red dot" Nikon F3 screens). If you use late Nikon F screen frames (with either yellow or red markings) you can do the swap with no problem, were you using regular F3 screens of "red dot" F3 screens or F4 screens.

See this :

http://www.destoutz.ch/typ_focusing-screens.html
 
You must log in or register to reply here.
Back
Top Bottom