Nikon FM and 20mm AI

[Justix]

I bought a Nikkor 20mm AI f4 lens for my Nikon FM. The focus microprism ring is dark on one end and i cant see to focus properly. Is this a fault or have i got the wrong lens type for this camera somehow?

 

[Ariston]

That lens should be fine as far as I know. Do other lenses work okay with the FM? The focusing screen may have been dislodged.

 

[abruzzi]

Being a slower lens, the focus aids will tend to go dark. You might try repositioning your eye in different places to see if you can get it to turn light. My pre-AI 28/3.5 has a tendency to turn the prism dark.

 

[jimjm]

Nope, lenses f:4 and slower on the FM will exhibit some darkening of the focusing prism. 3.5 and faster lenses do not do this on my FM. The focus screen is brighter on the FM2/FE2 bodies, so they look OK with f:4 lenses.
The FE came out a year later than the FM, so it may not have this issue, but it does have interchangeable screens, which the FM does not. It is a very good camera, though.

 

[tomkatf]

The 20/4 is a great compact lens. All comments above are correct... but the lens has so much depth of field you should be able to estimate distances and be OK even wide open, unless you're doing super critical close ups. If you set the lens at the hyperfocal distance (around 10ft), even at f/4 the depth of field is from aprox 5ft to infinity... Try using the DoF indicators Nikon has provided on the lens barrel itself. At f/16, set at the hyperfocal distance of around 3 ft(!) the DoF is from a little over 1.5ft to infinity, virtually universal focus. I used to use this method when street shooting (with a 28/2) to be able to snapshoot without fumbling for focus and missing a shot.

 

[Russ - SVP]

Being a slower lens, the focus aids will tend to go dark. You might try repositioning your eye in different places to see if you can get it to turn light. My pre-AI 28/3.5 has a tendency to turn the prism dark.

Yes. What Abruzzi said.

 

[Justix]

Thanks all for your help.

 

[Smaug01]

Justix, how do you like the lens so far? I've got focal lengths from 28 to 300 mm covered in my Nikon system. I'm thinking of adding either a 20 or 24 mm, or maybe even a ultra-wide zoom.

 

[tomkatf]

Justix, how do you like the lens so far? I've got focal lengths from 28 to 300 mm covered in my Nikon system. I'm thinking of adding either a 20 or 24 mm, or maybe even a ultra-wide zoom.

Not Justix but I can highly recommend the 20mm focal length. Very useful lens... If you already have a 28mm, I would go to 20mmm and skip 24mm. Unless you want both...

 

[Smaug01]

Not Justix but I can highly recommend the 20mm focal length. Very useful lens... If you already have a 28mm, I would go to 20mmm and skip 24mm. Unless you want both...

Thanks Tom. I had the 20/2.8 AF-D before and I liked it. Might be the same optics.

 

[tomkatf]

Thanks Tom. I had the 20/2.8 AF-D before and I liked it. Might be the same optics.

I've read(no personal experience) that the 20/2.8 Ai-S, is slightly better than the similar AF version... cite here: http://www.naturfotograf.com/lens_wide.html

 

[Smaug01]

I've read(no personal experience) that the 20/2.8 Ai-S, is slightly better than the similar AF version... cite here: http://www.naturfotograf.com/lens_wide.html

That is an awesome reference site; thanks!

 

[jimjm]

The 20/2.8 AIS is a great lens. Relatively small and very sharp.