Singer Librascope f1.8 300mm mirror lens

europanorama · Joined: 27 May 2012 Posts: 128

i have read about that and found out myself. it was evening infront of shop and it was not so bright. AF worked with contax AX. Vivitar 600/8 CAT.
pity was i had to sell Sigma 500/4 mirror. 15m version, 7m version was available. donut-f5.6 aperture built into cap. i have datasheet. on Contax AX wow. and today digital AF-capabilities.

eggplant · Joined: 27 May 2020 Posts: 516

Oh, I see.

How far can you focus down to using the AX alone?

europanorama · Joined: 27 May 2012 Posts: 128

Hadnt tested the built in 10mm extension. i never had the AX personally. it was in shop. you can calculate yourself. 15m(i had it) and 7m versions were available.
how near will bring 10mm extension? there is a forumula. there is always also 7.5mm contax-macro-ring. to go further down.
i tested closeup rings with 500/4 but i dont remember.
NB: rafcamera has also macroring for P67 to P6-cameras- 0.2-1m- Kiev 60-camera versions will also come. both normal adapters for infinity are in testing. P6-version has a handycap which will be altered. but its working. will open new thread when everything is nailed.one can already read in both FB forums about actual testings.

xaprb · Joined: 28 Jan 2021 Posts: 168

Can you explain more about “15m version, 7m was available.” What does that mean?

europanorama · Joined: 27 May 2012 Posts: 128

when i have time i will scan the leaflet. showing data of both 15m(i had it) and 7m versions. will then also show much beautiful images of ducks in the park. grayreiher against sun or in not well lit area is a bit soft. thats why i printed onto metallic paper. dark parts are better distinguished. not the same effect like cibachrome when one had to use masks.
but masking would improve any print. didnt shoot a lot with sigma 500/4 15m version. sigma sent me fax with date of last production. big heavy lens. without at least monopod one is quite lost.

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

I'm not familiar with these ultra-fast mirror lenses, but I do have more than a passing familiarity with long focal length cat telesccopes, specifically with apertures of 5" (1016mm focal length), 8" (2032mm focal length), and 10" (2540mm focal length), made by Meade and Celestron. One feature all these mirrors share is the means of focus. None rely on a coaxial focusing helical. They all have a knob located on the rear of the lens that one turns. It's a relatively fine focus arrangement and it is preferred over other focusing means, both because of the fine focusing ability and because the knob reduces the vibration that occurs when the telescope is touched to adjust focus.

Another thing just occurred to me. Often telephoto lenses of 300mm or longer will focus well past infinity --the reason given is because of internal expansion that may occur due to temperature changes. All mirror lenses I've owned focus past infinity. So, it seems to me that, people who are using the lens and trying for hyperfocal settings, if they aren't familiar with the lens's behavior at infinity, they might mistakenly focus past infinity without realizing it. Just a guess . . .

xaprb · Joined: 28 Jan 2021 Posts: 168