Microscope Objectives on bellows

[augusthouse]

I've been reading the posts on topics related to the use of objectives on bellows and have purchased some generic objectives to try out the approach.

I've arrived at the point where I need some advice regarding objectives.

Using the bellows it would appear from some of Rik's notes that 25x and lower mag. objectives are suitable.

I have a 10x and a 4x but I'm looking at buying a Nikon (produced in the 1980's -90s) version of these 2 objectives; but I get somewhat confused by all the specs.

Basically you guys know what would qualify to be suitable, so I thought I would ask here before buying things that I am unsure about, for eg, is a Nikon Microscope 85040 4X N Plan Phase Objective a good thing?

Sorry to be vague. I was just hoping for a few suggestions.

I have an EL NIKKOR 50MM F2.8 TO F16 ENLARGING LENS (black) on its way as well as a 40.5mm to 52mm (reverse adapter)and a 52mm to 52mm coupler which attaches to my Nikon BR2A reverse mounting ring on the front of my Nikon PB6 bellows.

The setup I am building is similar to Rik and George's. Needed to find the milling/drilling bench in Australia due to the freight charges for such items from OS. Main lighting source will be fiber optic and diffusers.

I realise that these are only the tools and the magic comes with experience and experimenting; but I'm up for that.

Basically, at this stage I'm of the mind to go for a 3x (Charlie mentions it in regard to his microscope and it sounds like there is something 'sweet' about this particular Nikon objective). I also have my eye on a Nikon 4x and 10x and eventually a 20 - 25x.

As with camera lenses, there are some which are 'just right' and I have no doubt that is the case with some objectives also; but like the EL Nikon that I purchased, still what you would call, 'affordable'.

I'm using a Nikon D100 and gradually working my way up the 'learning curve' of Stacking Software and I am reasonably comfortable with Photoshop.

Hopefully I'll have some photographs of unusual critters from Australia to post in the forum; but come to think of it, even the usual ones look spectacular under high magnification.

Craig Gerard

[rjlittlefield]

Craig,

The key thing I've found with objectives is to be sure that there's enough working distance.

Sometimes the best corrected objectives get that way by having more or thicker lens elements in front. This can whittle away at working distance. In some cases it's more like chop it off. I was ready to bid on a Zeiss 10X Plan Apo NA 0.32, until I asked two sellers what the working distance was. Based on measuring the objective, one of them said "around 1 mm", and the other one said 0.3 mm!

Working distance in the 5-10 mm range is not too hard to deal with. My 20X is spec'd at 3.3 mm. It's a bit challenging.

I don't know anything about the particular objectives you're looking at. If they're made to the DIN standard (which is my best guess), then working distance can be calculated as 45 mm minus the length of the objective measured from where the mounting shoulder fits against the turret. At this Edmund Optics link, it's measurement "A". For use on bellows, JIS objectives work fine too, but in that case working distance is 36 mm minus the length.

The objectives that I use are not "plan", just basic achromats. They have noticeable curvature of field, but that doesn't matter much because it's small compared to the depth of the slab that I assemble by stacking.

Hope this helps!

--Rik

[DaveW]

There are always the Macro Nikkors used on the Nikon Multiphot if you can still find them, like the 19mm:-

http://www.macrolenses.de/ml_detail.php?ObjektiveNr=29

The range is:-

Nikon, Japan Macro Nikkor 19mm 2,8
Nikon, Japan Macro Nikkor 35mm 4,5
Nikon, Japan Macro Nikkor 65mm 4,5
Nikon, Japan Macro Nikkor 120mm 6,3

I believe most of the range are RMS screw.

DaveW

[georgedingwall]

Hi Dave,

There are always the Macro Nikkors used on the Nikon Multiphot if you can still find them, like the 19mm:-

DaveW

You'll need deep pockets to buy any of these lenses Dave. When I was looking into using microscope objects for my own setup, I came across this website which gas these lenses for sale.

http://www.webwoods.com/stonemills/inde ... oppingCart

At a $1000 a pop, I don't think I'll be buying one any time soon.

Bye for now

[DaveW]

Its a case of if you drop across them somewhere cheap George. Like a surplus stores that sell ex government stuff etc, or an auction of ex public sector equipment. Our local, what would have been called at one time of day army surplus stores, has quite a few ex military and public sector migroscopes etc. They also have a jet engine in the yard if you want one!

DaveW

[rjlittlefield]

I would definitely start off with an honest-to-gosh microscope objective. I have no hands-on with the Macro Nikkors. I do, however, own one of the Zeiss Luminars that are widely reputed to be equivalent (and similarly priced). It's the Luminar 16mm f/2.5, the highest magnification of the series. It's a very nice lens -- wonderfully flat field, no CA. However, for resolution, a basic 10X NA 0.25 achromat objective is noticeably sharper than the Luminar. See the third panel of pictures in this post. The objective is also likely to be much cheaper.

--Rik

[Charles Krebs]

Craig,

Nikon Microscope 85040 4X N Plan Phase Objective a good thing?

Perhaps, but not for your intended use. I would avoid "phase" or "phase contrast" objectives. They have a dark annular ring in the rear of the objective that is necessary to obtain phase-contrast lighting when used with a matching microscope condenser. But this would serve no good purpose the way you will be using it, and might (?) even provide a lesser quality image than a non-phase objective.

As Rik has shown, microscope objectives can work very well for these shots, but as far as selecting an objective it is probably a matter of try it, and see how it works.

The working distance is one key characteristic you can assess before hand. Looking through my Olympus info I can see quite a variety in working distances for a different "model" of the same power objective. For example the following are working distances for several 10X Olympus LB series objective:
0.55mm, 1.10mm, 7.5mm, 7.18mm

And a few working distances for various 20X:
0.55mm, 1.5mm, .83mm, 1.63mm

This is just to show that there is considerable variation in working distances even with DIN objectives of the same power. Generally the high priced Apo's and Plan Apo's have the shortest working distances. Also, once you go over 10X working distance is a serious issue.

Most older objectives were designed to produce a useful image circle of about 20mm when used at the proper tube length (extension). Some will produce "quality" image circles of 26mm or more. The diagonal of the Nikon DSLR sensors is about 28mm. So you could expect that if you subject has very fine details out to the edges of the frame there may be some fall off in image quality with some objectives. Since most older objectives used the eyepiece to make final optical corrections, the amount of uncorrected chromatic aberrations in an objective (used by itself) will vary as well. The only relatively common "older" objectives that were supposedly corrected all in the objective were the Nikon "CF" objectives.

The Nikon 3X I have is sort of an odd duck. I don't know what scope it was made for or it's exact vintage. It's rather old, and has an unusually long working distance. It has a built in diaphram (which I never use, as optical quality drops fast when I do). It's low in color fringing, but the image quality will diminish somewhat if I use more than about the central 15mm of image circle.

Charlie

[augusthouse]

Thanks for all the responses guys.

This is exactly the information I was hoping to receive. The forum is priceless.

Craig Gerard
Australia