Intriguing objective

[Rossf]

Can’t remember where I saw it but recently saw a photo of a Zeiss objective-probably from neofluar era by the look of it but was changeable from 1.6x to 5x via collar-has anyone used this particular objective?-maybe there’s a downside to it but an appealing idea-to have all your lower mags provided by one objective. Saving precious rms holes!
Ross

[photomicro]

Can’t remember where I saw it but recently saw a photo of a Zeiss objective-probably from neofluar era by the look of it but was changeable from 1.6x to 5x via collar-has anyone used this particular objective?-maybe there’s a downside to it but an appealing idea-to have all your lower mags provided by one objective. Saving precious rms holes!
Ross

Yes, this one;

1.6-5x.jpg (68.84 KiB) Viewed 4163 times

[apochronaut]

Variable mag. systems or "zoom" systems tend to be limited by the number of moving elements in the system. The more the moving elements, the more likely it is that the compensation for aberrations through the range will be adequate and the image quality will be consistent. That is for a system that has edge to edge sharpness and compensation though, and this objective is described as a plan achromat; probably good to 18mm I would guess. So, given it's plan designation, one should have reasonable expectations of performance. I'm also guessing that they were expensive.
One red flag is that it is being described as being useful for accurate micrometer matching, kind of a single purpose objective and in that capacity plan performance is necessary but not necessarily good plan performance. I would think that if your intentions are for a scanning objective with a variable mag., as opposed to one that you want to rely on for photography, then it should do well. Obviously, I never used one but I am interested in the idea and how well it works.

[MichaelG.]

Variable mag. systems or "zoom" systems […]

Whilst I accept that the distinction has become blurred with common usage ... it’s perhaps worth noting that a “zoom” lens [supposedly] maintains its focus with change of focal length.
[which 46 20 13 clearly does not]

MichaelG.
.

Edit: The objective gets a brief mention here:
http://www.microscopist.co.uk/about/my- ... icroscope/

[apochronaut]

note, zoom in quotations. in practice, there are so many such systems that push the envelope of parfocality. many zoom stereo microscopes are so inclined. I think the Bausch & Lomb Dynazoom compound microscope with it's modest 2:1 zoom ratio was a classic parfocal design but I am not 100% sure. Does anyone use one and know for sure?

[MicroBob]

Here in Germany the Zeiss Standard line is loved by the amateurs. Especially good objectives are common knowledge and they hold their price to some extent. I have heard of this objective before but never had the impression that anybody were on the lookout for one and would pay a lot of money for it. The stated numeric apertures are on the low side but would still be able to offer good performance. The missing parfocality might be a disadvantage. But the Plan 1:1 also is not parfocal...

Bob

[MichaelG.]

note, zoom in quotations.

Already noted ... No argument intended: I was simply sharing a ‘fascinating fact’

MichaelG.
.

For the curious: https://en.wikipedia.org/wiki/Zoomar_Lens

[Rossf]

The main appeal for me was to be able to film the larger microbes in incidental light near window with makeshift back reflectors (large nematodes,water bears,etc) before going into transmitted light photography-I’ve filmed nematodes/tardigrades using this technique with a Leitz 1.5x with good W.D-slightly dry compost-add water drops and all these larger microbes started emerging and getting active-of course they are semi transparent but definitely imagable-wanted to show them in their actual environment first before going to drops of diluted specimen and slides etc-shame the working distance gets so small-I guess at the 5x end-most 4-5x have a pretty good working distance (not talking plan apos of course!)-thanks for the info peeps-keep well ross

[Microworldofgems]

When I started my Zeiss build a few years ago, this was one lens that I was in search of. Scarodactyl on here kindly let me know that he had acquired such a lens and we made arrangements so that I now have it. While I haven’t used it extensively as my Zeiss is primarily set up for epi illumination, I have used the 1.6-5x lens a couple of times and have been quite happy with it. Most of what I examine requires relatively low power magnification so this lens was spectacular in helping to compose a field of view appropriate for my subjects, especially when combined with the optovar. It is not parfocal however, so when the magnification. Is changed, you must refocus.

[Microworldofgems]

This is an image I shot with this lens. It is a stack of about 80 images rendered with helicon focus. It is an etched cavity in an aquamarine beryl crystal with some oblique fiber optic lighting with modified Rheinberg illumination also.

[Rossf]

Microworldofgems thanks for the info-it does sound temping but when prices are out of hand I think of the old German saying “even gold can be bought too dear” applies-the picture you posted is really beautiful. All the amazing photos of metallurgy or polarised light I’ve seen on this forum inspired me to start experimenting with this microscopic technique-
Regards ross