Nikon 40x SLWD CF M Plan Achromat

NikonUser · Post by **NikonUser** » Sat Oct 31, 2009 11:50 am

This 210mm tube length, RMS-threaded lens has a NA = 0.40 and WD=14.9mm (cf. similar 40x ELWD, NA=0.5, WD=10.1mm).

On my system, the minimum extension I can get (with bellows) is 145mm. This gives a mag. of 29.6x on sensor. I must try it without bellows, perhaps can get a decent image at 20x.

This lens gives an acceptable image at 30x mag.

Scales on wing of Canadian Tiger Swallowtail (butterfly)
Top image: 32 frames @ 0.002mm, 29.6x mag on sensor; full frame; ZS Pmax
Bottom image: 54 frames @ 0.001mm 40x mag on sensor; full frame; ZS PMax.

NU09225

NU09226

rjlittlefield · Post by **rjlittlefield** » Sat Oct 31, 2009 12:13 pm

Beautiful!

I'm curious about the illumination. What's the setup?

--Rik

Charles Krebs · Post by **Charles Krebs** » Sat Oct 31, 2009 12:36 pm

NU...

This lens gives an acceptable image at 30x mag.

I think more than just acceptable!

And the 40X looks great. Nice!

I think sometimes we need to step back a little and contemplate... we're talking 30X and 40X! That means.. left to right.. the field size in the 40X shot is 0.59mm or 0.023 inches. Less than 10 years ago (before "stacking") you could not imagine getting an image like this with the relative ease we do now, if at all.

With a NA of 0.40, it will not resolve detail any finer than with the 20/0.40 ELWD. So it would seem that results using the 20/0.40 would be very close if that were used with greater bellows and/or cropping to get the same image size. My "sense" is that, at 40X, there seems to be a slight image quality advantage by using the 40/0.40. (But I've never done a very careful "head-to-head"). And likewise, there's a slight benefit to the 0.50 NA of the 40X ELWD.

However, the working distance can, at times, be a big asset...

Working distances:
40/0.40 SLWD 14.9mm
40/0.50 ELWD 10.1mm
20/0.40 ELWD 10.5mm

I don't use the one I have anywhere near as much as the 10X and 20X, but there are a a few shots taken with this objective here , here, and here.

NikonUser · Post by **NikonUser** » Sat Oct 31, 2009 4:38 pm

Rik: The image is from the dorsal surface of the left hind wing of a pinned spread specimen. Illumination with a single flash positioned at the apex of the right fore wing and very close to the wing so as to create a shadow beneath each scale. Raw flash, no diffuser.

Charles: I was aware of your superb images with this lens. I assumed you were using it at the 210 mm tube length at 40x. I was interested in seeing how this lens performed at a lower magnification. I can't see myself needing 40x very often, or even needing 30x but it's nice to know that if I need 30-40x then this lens will do the job.

I am in the market for a M Plan 20x ELWD, one I bid on recently went for over $600.00.
I see the CF BD Plan 20x ELWD offered more frequently than the M Plan - what is the thread size on this lens?

Charles Krebs · Post by **Charles Krebs** » Sat Oct 31, 2009 4:52 pm

NU....

I'll need to measure the Nikon "BD". The Olympus "BD's" were 25mm and then they switched to 26mm ( annoying

). I'm pretty sure the Nikon ones are 26mm (but I'll check. Don't know the pitch.)

The thread size is a nuisance, but it's really easy to unscrew the outer "darkfield" sleeve on the 20/0.40 ELWD. This then provides the same working distance as the non-BD version with a front diameter that is significantly narrower. (So that's a little bit of a "bonus" to make up for dealing with the larger mount size).

dmillard · Post by **dmillard** » Sat Oct 31, 2009 5:24 pm

NU -

These are really nice - the shadows provide a sense of depth that would probably be missing with greater diffusion.

David

Eric F · Post by **Eric F** » Sat Oct 31, 2009 5:27 pm

Excellent butterfly scale shots NU! That 40x SLWD lens is giving you splendid results at both 30x and 40x. Your staging for these very fine slices (1 micron) must be very solid; lighting is perfect -- great job.

Eric

rjlittlefield · Post by **rjlittlefield** » Sat Oct 31, 2009 6:55 pm

In taking another look at these lovely shots, there's something I'm puzzled about.

Look at these crops of corresponding regions, and contemplate those little triangular features that I've circled. The intense one on the right looks like a real feature of the wing scale, but there's no trace of it on the other image. Then there are all those other instances that almost look like "echos" of the intense one. I have no idea what's going on here. Help?

--Rik

ChrisR · Post by **ChrisR** » Sun Nov 01, 2009 12:02 am

Dodgy software Rik. The stack's crashed. Those are wayward indirection pointers...

ChrisR · Post by **ChrisR** » Sun Nov 01, 2009 2:24 am

I am in the market for a M Plan 20x ELWD, one I bid on recently went for over $600.00.

I have a "spare". Swap you for some dead flies, or something?
I'd better check they're about the same, I'd hate for you to get one much better, or worse, than the one I keep!

NikonUser · Post by **NikonUser** » Sun Nov 01, 2009 5:57 am

ChrisR:
Consider this scenario:
You want a good representation of the fly (or moth) fauna of SW New Brunswick; vs You want a 20x ELWD lens.
The latter can be obtained for a lot less than $1,000.00

The former cost me $80.00/day in out of pocket expenses (petrol & accommodation) a few years ago. If one collects just 1 day/week (not sufficient), a Summer's collecting for 20 days would cost $1,600.00. Sorting, pinning, labelling, and perhaps identifying would take most of the Winter.

Having to spend 1 or 2 nights a week in the woods is hazardous to one's health- apart from the mosquitoes, the hazardous part being explaining it to the missus.

NikonUser · Post by **NikonUser** » Sun Nov 01, 2009 7:14 am

Rik
I hadn't noticed these triangles so I checked the individual frames. This is what I believe happened.

1st point: 2 camera bodies were used; the sensor (or filter) on body 1 is clean, that on body 2 (used for the 40x mag) has really minute dust spots.

2nd point: my Nikon focus block does not move in an absolute straight line but travels forward in a very small circle. This is noticeable at the 0.001mm increments.
Thus every frame is slightly out of alignment but after about 5 frames it's back to where it started. ZS seems to correct the alignment for the scales. For the dust spots it seems to fill in the gaps between the frames and make the spots triangular.

I guess these dust spots are so small that they don't register at my more normal 5x mag.

Another hazard when shooting at 40x, in case we don't have enough already

NikonUser · Post by **NikonUser** » Sun Nov 01, 2009 8:45 am

The 40x SLWD seems to be quite a versatile lens.
Used with just 28mm extension (designed for a 210mm tube length) it gives a mag of 15.8x on my 23.7mm sensor.
Full frame of a portion of a Canadian Tiger Swallowtail. Insert is the actual setup showing the extension and the nice working distance.

NU09227

rjlittlefield · Post by **rjlittlefield** » Sun Nov 01, 2009 9:45 am

NikonUser wrote:Rik
I hadn't noticed these triangles so I checked the individual frames. This is what I believe happened.

1st point: 2 camera bodies were used; the sensor (or filter) on body 1 is clean, that on body 2 (used for the 40x mag) has really minute dust spots.

2nd point: my Nikon focus block does not move in an absolute straight line but travels forward in a very small circle.

Dust spots combined with cyclic motion makes perfect sense. That possibility had not occurred to me.

Thanks for the analysis!

--Rik

AndrewC · Post by **AndrewC** » Sun Nov 01, 2009 12:29 pm

NikonUser wrote: I guess these dust spots are so small that they don't register at my more normal 5x mag.

How does that work then ? You are talking about sensor dust bunnies aren't you ?

Andrew