APO 2x Extender out of focus

[retcheto]

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Is it possible for an APO 2x extender to be out of focus and need calibration? I've been using it with a 180mm APO Telyt and my images with the extender are out of focus. I'm focusing on distant mountains at infinity. It's possible I didn't have my tripod secure enough, I'll have to do some more testing.

[a.noctilux]

Many reasons to have "not really sharp pictures" here:

- distant mountains means turbulance of air and maybe dust in atmosphere

- 2x Apo-extender-R with Apo-Telyt-R 180mm may need rigid support

- how was made the focussing: if the lens is set at infinity mark there may be problem of "how extender was designed" for SLR

- Extender designed with the "ground glass focussing in mind" = a bit "short" to allow easy focussing on distant object,

  so when the lens + extender is focussed "almost infinity" there is more focussing movement to simplify "ground glass focussing" (in SLR days)

[rpittal]

Which camera are you using and how are you focusing? Live view on an M10 or M240 with EVF should be OK. I use mine (apo180/3.4 and apo2X) mostly on SL which is fine (both with and w/o extender). Relying on infinity mark on lens (especially not on the native R camera) is not likely accurate. Adapters are usually a bit short to ensure being able to focus at infinity. The lens by itself may be OK, but the extender adds magnification which makes focus more critical and also another opportunity for inconsistent flange distances. Great lens, but obviously requires extra care with focus.

[Peter Kilmister]

I have used a Leica Televid attached to my M240 using a T adapter and an extension tube. It was to capture a harvest moon which I achieved.

 

However, it was no good setting the Televid to infinity and hoping for the best. I really had hard work getting the Televid to focus on something that is so far away it took until 1969 before anyone walked on it.

[retcheto]

I'm using an M246. I just set the focus to infinity and assumed it would work, that's probably where I went wrong. The shots with just the 180mm Apo-Telyt-R were sharp when I focussed at infinity and I assumed the extender wouldn't change that. I'll have to use liveview or the EVF next time

[jmahto]

I'm using an M246. I just set the focus to infinity and assumed it would work, that's probably where I went wrong. The shots with just the 180mm Apo-Telyt-R were sharp when I focussed at infinity and I assumed the extender wouldn't change that. I'll have to use liveview or the EVF next time

Inifity mark on the lens will *not work* with 180 APO (or with any long lens). They all go past infinity yo accommodate for adaptor thickness/thermal expansion. You *have to* use LV/EVF for accurate focusing. I have noticed that the correct focus is slightly before infinity mark but I will never rely on the distance scale for any long lens.

 

2XAPO extender puts it out even further and you will have to back off a little more in the distance scale, using LV. I think it is a good thing to have some extra movement on the infinity side to accommodate for adaptor thickness variation and thermal expansion.

Edited January 29, 2018 by jmahto

[mmradman]

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Infinity mark is no guaranty that distant image will be in focus, I discovered that even extra wide lens cant' be relied on by the infinity mark method.

 

One example; As R lenses are not RF coupled I tried infinity mark method with M246 and external optical VF for framing and Elmarit R 19mm Mk2 via Leica's latest R-M adaptor, I used typically f8.  Images were OK sharp at low magnification but far objects were definitely out of focus at maximum magnification.  I did re-shoot similar scene this time using external EVF distant objects typically over 100 m [330 ft] away corresponded to a focus setting between 2-5 m or approx 10 ft on the focus ring. Hyperfocal for f 8 and 2-5 m focus setting runs from 1 m to beyond infinity on the lens focus scale.

Edited January 29, 2018 by mmradman