spiratone 20mm f2.8 infinity focus issue

hello, i am not sure if this should go to 'classic manual cameras' or here in to the nikon subforum.

 

so, i have a nikon n2000, two of them. I have 50mm f1.8, and chinar 28mm f2.8. both work fine.

 

i recently obtained spiratone 20mm f2.8, so the issue is, when it's on camera, any of them, and i put the focus to infinity sign, then in the viewfinder, the lines are still broke by the line in the circle.

 

 

you know, you see a circle and an intersecting line, and this line divides the lines you see, and if the line in your scene is broken by the line in the lens, then the focus is not on that object the line belongs to. you need to rotate the focus ring so that the line of the object you are aiming to keep in focus become uninterruptible.

 

so, with this spiratone, at least on my cameras, this line is always broken.

 

my impression is, this spiratone lens have been made specifically for nikon.

 

what do you think? is it normal? does it mean the lens are not calibrated?

i did not have the results yet, but when i keep the focus on infinity, and shoot buildings, does that mean the building will be out of focus, because its lines are interrupted in the viefinder?

or may be on another nikon camera the lens will work okay?

thank you.

It is an OLD lens. It may have been knocked out of alignment, the focus scale could have rotated, or it was improperly "fixed" in the decades since it was first sold.

Do NOT focus on infinity on the lens, focus with the viewfinder. Although with DoF at f/8 it probably won't make any difference.

Do NOT focus on infinity on the lens, focus with the viewfinder

Yup, +1 on that.

 

If you can't get the lines to align on a far off building, power line, tree etc return it. It's either been opened up and reassembled badly or has taken a big knock somewhere.

 

my impression is, this spiratone lens have been made specifically for nikon

Yup again, those little shiny chrome 'bunny ears' are unique to Nikon, so yes it is meant to be used on a Nikon only.

Spiratone didn't make anything, they just re-badged it. From the style, that's almost certainly a re-badged Tokina made lens. Hope you didn't pay a lot for it.

 

What others have said, plus buildings are never at infinity. So I presume the lens focusses short of infinity. A knock hardly ever does that without leaving major physical damage. So my guess is it's been inexpertly 'repaired' in the past.

 

Having said that - it's worth checking that the rear lens assembly hasn't worked loose and partially unscrewed itself. A quick grip and twist with your fingers (if possible) on the rear elements of the lens should tell you if this is the case. Don't touch the glass itself though, just the black barrel.

plus buildings are never at infinity

 

err, nothing is, that's the point.....;)

err, nothing is, that's the point.....;)

 

- Yeah, but what's the rear depth-of-field at infinity? I think we need Buzz Lightyear's input at this juncture.

I think my DoF app. has just crashed....:(

Could be its focusing slightly past infinity some lenses do this.

First, the "broken line" in the center of the viewfinder is called a "split image rangefinder".

 

As noted above, don't focus the lens on infinity and expect even distant objects to be in focus. Use the viewfinder and the tools that it provides.

 

Many lenses will turn and focus past infinity. This is done for a number of engineering reasons including thermal expansion and loose manufacturing tolerances.

 

From what you say, the split image works correctly on the other lenses? It may be that the problem is with the camera body.

With such a wide lens, even the drying out of lubricant can allow it to droop forward so that you can't reach infinity. The solution might be a lube job, and have the tech make sure the focus is right afterwards. This is an easy adjustment, but you have to be both clever and gentle with a screwdriver.

i took it to the local camera repair store, and they were able to fix it.

 

thanks to all.

FWIW, I like the moon as an infinity target.

 

It's certainly further away than any terrestrial objects you can see from sea level, and for all intents and purposes for our applications on our cameras it's at infinity. It has a defined edge line for a split image, and is bright enough to both make a microprism "disappear" and to see easily to line up a co-incident rangefinder.

i took it to the local camera repair store, and they were able to fix it.

 

thanks to all.

 

So what was the problem?

So what was the problem?

he refused to explain. sort of arrogant, said - does it matter to you, you won't understand anyway.

he refused to explain. sort of arrogant, said - does it matter to you, you won't understand anyway.

 

My guess is that he was avoiding getting into a half hour explanation of what he did. That half hour is not billable, so he is loosing money, vs. working on another repair.

yeah, may be. (:

FWIW - here's a Spiratone 20mm f/2.8 from Spiratone's Catalog of 1985.

Miss them, I do:(