Nikon scope objectives.

ChrisR · Post by **ChrisR** » Sun Jul 19, 2009 3:36 am

I'm looking for info on the various recent but now discontinued Nikon microscope objectives we could put on bellows. The working distances of the M plans, CFs and BDs would be useful.
I have a 10x BD 0.25 which has a good (several millimeters) WD with the outer "shell" removed. Mine was recently $50 on ebay, which doesn't seem to be exceptional.

Is an extra bit of NA worth chasing?
With resolution given by 0.61λ/NA
which is about 0.34/NA
So NA 0.25 and 0.3 lenses would give 1.36μ and 1.13μ.
When magnified x10 onto your sensor which may have a pixel size of say 5μ, thats the difference between 2.72 and 2.26 pixels of blur.
I think it would be very difficult to say which lens had been used, without a super-critical comparison?

REF

Harold Gough · Post by **Harold Gough** » Sun Jul 19, 2009 3:42 am

Chris,

Have you looked around this website?

http://www.nikonians.org/nikon/

Or this:

http://forum.mflenses.com/manual-lenses-f3.html

Here is a comprehensive review article:

http://bythom.com/rationallenses.htm

Another:

http://www.mir.com.my/rb/photography/co ... /index.htm

Here too?

http://www.nikonlinks.com/equipment_lenses_macro.htm

http://homepage2.nifty.com/akiyanroom/r ... amily.html

Not being a Nikon user, I don't know how up to date the above are.

Harold

ChrisR · Post by **ChrisR** » Sun Jul 19, 2009 4:14 am

Thanks for the links Harold.
I didn't know of all of those. I did mean microscope objectives though (title is unedited!). Not many of them get a mention.

lauriek · Post by **lauriek** » Sun Jul 19, 2009 5:19 am

I ran one comparison between my M plan 10x/0.25 vs my N plan 10x/0.30 and I could not tell any difference in terms of resolution/sharpness...

Peter M. Macdonald · Post by **Peter M. Macdonald** » Sun Jul 19, 2009 8:16 am

Chris,

There is useful dscussion of this at http://www.photomacrography.net/forum/v ... 2&start=15. In particular, see the post by Charles Krebs from 26 March, 2009. The links there are very useful. The first is for finiteobjectives, the second for the newer infinity series.

The brchures both give details of CF objectives, i.e. ones designed not to need atube lens or compensation for chromatc aberation in the eyepiece. Working distances are also given.

Hope that this helps.

Peter

ChrisR · Post by **ChrisR** » Sun Jul 19, 2009 9:43 am

Thanks for the reminder Peter I knew I'd seen some somewhere.

The BDs remain ( the fat ones with the 25 or is it 26mm mount)
I'm not sure if there's more than one type within those; the prices to be seen do vary a lot.
And I'm not sure all the M Plans are covered.

One point I note from the older lenses with finite tube lengths of 160 or later, 210mm, would be that the focal length must be different. Some users have reported that a particular lens can be used well off its designed tube length without losing IQ.
So the FL becomes important. I'm sure I've seen it written here that the FLs must be 16mm and 21mm for x10 lenses, which feels right but I'm not sure is true - or am I just getting confused by the WD?
If it IS, of course, the 160 lenses will give higher mags at the same extension.
This is of interest to me because I have a 24x36 sensor, which needs more mag, and more coverage..

Harold Gough · Post by **Harold Gough** » Sun Jul 19, 2009 10:59 pm

ChrisR wrote:I did mean microscope objectives though

Whoops! I should have checked back before I got carried away. At least, it is fairly comprehensive misinformation!

Harold

Charles Krebs · Post by **Charles Krebs** » Mon Jul 20, 2009 12:32 am

Chris,

There's a pretty good reference here for some of them (the bottom charts are the finite 210mm tube length variety)....
http://www.optotek.net/Microscope_Inven ... tives.html

I've got some other info somewhere, I'll see if I can find it and scan it.

In the 160mm tube length "biologicals" there are not too many that are useful in this manner, primarily because of the working distances. The 4X and 10X CF N Plan Achromats (and the 4X CF N Plan Apo) are about it.

The CF M series is more expansive, and there are quite a few that can be used on camera bellows. The BD (brightfield/darkfield) versions have the hollow "collar" around the optics in order to allow for darkfield illumination on a microscope with a vertical illuminator. These collars jut out past the front element, reducing the working distance. The "collars" are pretty easy to remove, and then they will have the same working distance (and optical quality) as their "M" counterparts. (But you need to fill in the opening provided for the darkfield light, and you must deal with the larger (26mm I believe) thread mount.

A big question-mark for me is using the full frame camera (24x36mm) with these. Used at the designated tube length you will really need to check carefully to see if the images you are getting are satisfactory beyond about a 28mm diameter central circle. I deliberately use the smaller sensor cameras with these lenses on bellows. (The smaller Canon has a sensor diagonal of 27.3mm). I seriously doubt some of these optics will cover the 43.3mm diagonal of the full frame sensor with good quality out toward the edges. But I'll admit I haven't tried it so I might be surprised. As to losing image quality when extending beyond designated tube lengths, the numerical aperture matters more than the focal length. These N.A.'s are pretty forgiving of variation in the tube length, so a larger "quality" image circle could be obtained with more bellows (higher magnification). But you do reach a point where the image would be better by jumping to a higher power, higher N.A. objective. For example, if you extend a 10/0.25 to 20X, you'll get a larger image circle, but the effective aperture would be around f42... serious diffraction softness. A 20/0.40 used at 20X would have an effective aperture of about f26... still into diffraction losses with DSLR's, but nowhere near as severe as with the 10/0.25.

I'm a little hesitant about opening up this subject

but it may be possible to get larger image circles using some of the infinity objectives such as those made by Mitutoyo. See page 26 in this catalog:
http://krebsmicro.com/MitutoyoE4191-378.pdf
These should be used with a tube lens. The Mitutoyo tube lenses are expensive and I've only seem one for sale on Ebay in five years. The objectives are not exactly cheap either! But they have impressive working distances. Not too long before I had to pack up stuff for my move I had set up a 5/0.14 Mitutoyo M Plan Apo (wd=34mm) using a Nikkor 210mm Apo process lens as a tube lens. Works great, but makes for a big clunky arrangement on the bellows. If I ever get set up again

one of the first things I'd like to see is just how this looks on a full frame sensor.

Charles Krebs · Post by **Charles Krebs** » Mon Jul 20, 2009 9:55 am

I've scanned a "Nikon CF Objectives 210 Tube Length" brochure/pricelist and put it up as a PDF file here:
http://krebsmicro.com/mplan.pdf

ChrisR · Post by **ChrisR** » Mon Jul 20, 2009 3:12 pm

Thanks again Charles. Those and the others are now copied to one directory which I hope I'll be able to find in future.

As it happens I was looking at Mitutoyos earlier today, on sale eg
here where I was actually looking for translation stages..

I have a Nikon BD10x, non "DIC" , also a 5x.
I found the illumination annulus easy to seal shut with a rubber O ring, but then I have about 200 different sizes in the van.
I haven't a great way to mount the BD lenses. I used a rubber bush designed to seal between two UK waste pipe fittings, between the 26mm and a 39mm extension tube. I haven't seen a proper adaptor which costs less than the lenses did, yet.

I take your point about sensor coverage.

Unless something physically gets in the way, if you go out from 20 to 30 mag on a 20x lens, then you're looking at the middle of an image which has to be 3/2 times the diameter, yes? Somebody said one of the popular lenses, the 20 ELWD I think, covered full frame.

I'm curious about your trials with an infinity lens - you know what's coming, which is a justification of your hesitation in raising the matter...
Did you try it without the extra lens? Poor??
If a 160 lens (image cone about 1.8º) works OK at 270mm (for 30x instead of 20x) , (image cone about 1º) then it might not be so bad at 0º!
Why that particular lens? Would any decent camera lens do? I mean, if the resolution from the scope lens is only good enough to show a point covering

, a 50/1.8 would more than cope.

Charles Krebs · Post by **Charles Krebs** » Tue Jul 21, 2009 4:29 pm

I used the 210mm Apo Nikkor because it is an excellent, small lens with a focal length close to the Mitutoyo tube lenses (200mm) and I had it sitting on a shelf doing nothing, so ...

I didn't try a comparison with the objective alone.

I mean, if the resolution from the scope lens is only good enough to show a point covering , a 50/1.8 would more than cope.

Actually a 5/0.14 and a 10/0.30 used on bellows are capable of resolution that most sensors cannot fully accommodate. It's at the higher magnifications where the "demands" of sensor resolution drops off quickly.

ChrisR · Post by **ChrisR** » Tue Jul 21, 2009 5:03 pm

Actually a 5/0.14 and a 10/0.30 used on bellows are capable of resolution that most sensors cannot fully accommodate.

Oh?
10x NA 0.3

10 x1.13 = 11.3microns.
Many a DSLR sensor pixel is smaller than that?
Am I missing something?

Charles Krebs · Post by **Charles Krebs** » Tue Jul 21, 2009 5:42 pm

The smallest resolvable detail a 10/0.30 can produce is 11.2 micron at the sensor. In order to resolve all the detail there must be an bare minimum of 2 pixels across this detail. But that is only if everything is totally serendipitous with the way pixels line up with detail. Most references I've seen suggest that it is best to have 3 to 3.5 pixels for the smallest resolvable detail size.

So... if you have a 24x36mm sensor and the objective is producing a quality image over all the sensor (which as I mentioned earlier is not likely, but for this discussion it doesn't really matter) then the pixel size and count of the sensor would need to be as follows:

2 pixels per smallest detail:
largest allowable pixel 5.6 micron
sensor needs 27.6 Mp

3 pixels per smallest detail:
largest allowable pixel 3.7 micron
sensor needs 39.4 Mp

3.5 pixels per smallest detail:
largest allowable pixel 3.2 micron
sensor needs 53.7 Mp

Look over this spreadsheet:
http://krebsmicro.com/relayDSLR/relay_micro.xls
There have been some "simplifications" here but it is revealing.

When the 35mm format was used on a microscope, there was typically a "relay optics" magnification of 2.5X (Cell B13 in spreadsheet. With direct projection, as on a bellows, this is "1"). It is somewhat surprising to see the huge difference between "2.5" and then "1" in Cell B13.

ChrisR · Post by **ChrisR** » Sun Jul 26, 2009 11:55 am

Thanks Charles.

A query remains: Nikon at some point designated their M Plan, BD and maybe other lenses as "CF".
Noting your warning to Lothiman about the lens you had in 2005 :
"Plan ACHRO LWD 10x / .25 WD = 10.5"

does that mean that any such lens NOT marked "CF" could be a chromatic duffer? I'm confused, because I think they didn't use chromatiic correction in tubes/eyepieces? Or did they?

And while I''m here, can "we" of the lens-on-bellows group, use lenses which are marked "DIC" or "Phase"? I've read about what they're for, but I'm not sure if anything like a ring would appear in the image?

Charles Krebs · Post by **Charles Krebs** » Sun Jul 26, 2009 1:57 pm

Chris,

A problem is that Nikon did not mark all of their CF objectives as such on the objective itself. This is certainly true of the majority of the CF 210mm tube length M and BD objectives we like so much, where most bear no "CF" designation. I don't really know about all the "biologicals". I have never seen one that was CF that was not so marked, but I am not very familiar with mid 70's Nikon biological objectives, so they may be out there. (The CF's appeared in 1976, prior to that, eyepiece correction was used). Also, instead of engraving, Nikon started to paint on lens data about that time (especially on the "biologicals"), and the markings really have a tendency to wear off. So sometimes it's hard to tell exactly what you are looking at.

Remember also that not every objective is a gem. Camera manufacturers and lens-makers produce a wide range of lenses from very modestly priced to very expensive. Some pretty poor, some very good and others are outstanding. So too, microscope manufacturers have a range of price points they need to accommodate. Plan Apo's are generally the highest quality series made but their working distances are usually far too small for our use. But there can be quite a range of quality in the Achromat and Plan Achromat offerings.

No problem with DIC versions. These are usually the same optical formula/construction, but selected for the DIC designation based on an exceptionally low amount of "strain" in the glass elements. Strain does not affect normal imaging, but presents difficulties with the complex polarization methods used in DIC. (DIC objectives generally cost a little more than their non-DIC counterparts).

I would probably avoid using a phase objective if I had the choice of a non-phase version. For a stack, the difference might be extremely small, but the objective's annulus certainly doesn't add anything positive. See this message:
http://www.photomacrography.net/forum/v ... php?t=6647