Not All that Glitters is Gold

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

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Chris S.
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Post by Chris S. »

Rich, either of the lenses you named stand a good chance of working with an infinity-corrected lens intended for a 195mm tube lens.

A bigger question with this bunch of objectives is the working distance. If it's 1.20 or 1.75mm, like the ones g4lab referenced, that would be very short for macro work. My 20x objectives have 10.5mm and 20mm working distance. If one is working only with flat, transparent slides lit from the back (as in the case of much microscopy), no problem. But for typical macro work (front lighting, non-flat subjects), WD's in the range of 1-2mm are highly inconvenient and or perhaps impossible to work with.

--Chris

PS--Is my memory off? The individual lenses have a $55 buy-it-now price. I looked at this auction when Craig first posted the link to it, and thought they were cheaper. Did it change, or am I misremembering?

naturephoto1
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Post by naturephoto1 »

Chris S. wrote:Rich, either of the lenses you named stand a good chance of working with an infinity-corrected lens intended for a 195mm tube lens.

A bigger question with this bunch of objectives is the working distance. If it's 1.20 or 1.75mm, like the ones g4lab referenced, that would be very short for macro work. My 20x objectives have 10.5mm and 20mm working distance. If one is working only with flat, transparent slides lit from the back (as in the case of much microscopy), no problem. But for typical macro work (front lighting, non-flat subjects), WD's in the range of 1-2mm are highly inconvenient and or perhaps impossible to work with.

--Chris

PS--Is my memory off? The individual lenses have a $55 buy-it-now price. I looked at this auction when Craig first posted the link to it, and thought they were cheaper. Did it change, or am I misremembering?
Hi Chris,

Thanks. There are apparently 2 separate listings for the lens, 1 for a single lens and one for a 30 lens lot. That is why many of us have been discussing possibly collectively buying the lot and distributing lenses to the membership. Below are the 2 separate listings:

http://www.ebay.com/itm/200718941277

http://tinyurl.com/6ulyb7m

Rich

Craig Gerard
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Post by Craig Gerard »

Chris,

The seller has them listed in a box of 30:
http://www.ebay.com/itm/360438163254

and also individually for $54.99 (originally there 109 available)
http://www.ebay.com/itm/200718941277

I asked the seller to perform a simple exercise to determine approximate WD.


Craig

*Just noticed Rich has also responded while I was typing 8)
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Chris S.
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Post by Chris S. »

I'm aware that there are two separate listings. My question was about the one first posted--the listing of a single optic. Did that price change?

Craig Gerard
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Post by Craig Gerard »

Not since I first saw it 24hrs ago.

Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

Chris S.
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Post by Chris S. »

Pending Craig's getting a response from the vendor, it's an interesting exercise to measure one of the pictures in the vendor's ad. In the analysis below, I've rotated the vendor's picture slightly to square things up with horizontal and vertical. The added lines and notes are mine. The 20mm assumption for the yellow line may be roughly correct if the objective has standard RMS threads.

Image

The approximate 32.5mm length of the green line is interesting. If the lens is standard DIN, it would be set up for 45mm parfocality. A space of 12.5mm between the front of the objective and the subject would suggest a long working distance optic. Given that I'm working with a slightly off-axis photograph--particularly one with in which a bit of bulging glass at the front of the lens might not be seen--and the barrel of the lens is missing, my number could easily be off by a few millimeters from the original working distance with barrel on, the new working distance with barrel off, or both. And again, this is assuming a DIN optic, which it may not be.

Now for another interesting bit. While the current (Mar 01, 2012) JML Website does not list a 20x finite DIN objective--nor any 20x objective with long working distance--the Google cache of February 19 for the JML Website lists two of them, which appear to have since been removed.

Here is the Google cache for the JML page as of about two weeks ago:

Image


Here is the JMP page as of today:

Image


It's intriguing that a number of optics have apparently been delisted from the JML site, right around the time that a major vendor lists a boatload of hemi-demi-semi-similar optics for sale, with the barrels removed. Could these be the apparently discontinued finite 20x 0.30 LWD? Arguing against it would be the seemingly large difference between my measured 12.5 apparent WD and the 5.8 WD claimed by JML. I'm probably off, but by that much? Did JML make an 20x with even longer working distance, which might have been discontinued even earlier?

Just noodling. I'm not interested in buying any of these, but a mystery is always fun.

--Chris

canonian
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Post by canonian »

Interesting!
After reading Chris S. assumptions I'm all ears and eyes on this topic, a 20X LWD would nicely fill the gap in my photo-optics.

g4lab
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Post by g4lab »

Just to thicken the plot a little note that the seller "sunnking" is in Rochester New York. As is JML. Who probably surpluses everything to sunnking.I betcha.

I'll make a couple of phone calls tomorrow.

Will Milne
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Post by Will Milne »

Isn't an NA of 0.3 for the possible LWD or even the NA of 0.4 for the possible regular WD 20x version mediocre at best? I suspect that there is a silent hope that this JML inherits the same CA free character of the 21 f3.5 but with those potentially low NA values it might also inherit the same borderline sharpness compared to alternatives?

Will

ChrisR
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Post by ChrisR »

The lens certainly looks like a LWD one of some sort from the front glass diameter.
These 20s have diameters(approx) and WDs as follows:

Code: Select all

                              dia     wd 
Nik 20 0.4 160   Mplan        3.7     2.7    
Nik 20 0.4 210    DIC         4.2     2.7  
Nik 20 ELWD 0.4 160   Mplan  10.25   10.5 
Unitron 20 ELWD 0.3 160       8.5    ?? 
Nik 20 SLWD  inf 0.35  CF    16.35   20? 
Nik 20 SLWD 210 0.35         16.3    19.9 
Nik 20 inf LU 0.5             4.0     2.1 
Mit/usmco inf 20 0.40        21.5     lots
Putting a ruler against the computer screen image of Chris S's, that glass would be about 8.2mm diameter.
So a WD something around 8mm could fit for a NA 0.3, if the lens design is similar.
If any of these made it to Europe, I'd feel deprived not having one...

ChrisLilley
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Post by ChrisLilley »

Harold Gough wrote:I don't know about the value of the lens but that is a very high worldwide mailing charge.
I am seeing US $54.99 for the item plus US $59.72 for postage (and multiple stern warnings tha tthey use UPS only) to which should be added 20% of the total (item plus shipping) sales tax on import plus UPS 'brokerage fee' which is typically at least as much as the tax they paid for you. So probably aroud US$ 150 all in.

The tray of 30 on the other hand has only US $118.26 for postage.

Having someone in the US do a group buy would result in significant saving I suspect.

ChrisLilley
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Post by ChrisLilley »

naturephoto1 wrote: The only lenses that I have to the best of my knowledge that I could use as a tube lens would be either my Leica 180mm f3.4 Apo Telyt lens or my Leica 70-210 f4.0 Vario Elmar lens.
Since the 180/3.4 is optimised for use at infinity (and is of excellent quality) , it would probably work very well as a tube lens here.

Peter De Smidt
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Post by Peter De Smidt »

If needed, I could help out...

conkar
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Post by conkar »

Here is another reference for a 20X JML objective:

Standard Achromatic Microscope Objectives

FL (mm): 9.0
Magnification: 20X with Spring
NA: 0.40
Working Distance: 1.7
Specifications: DIN Type (Shoulder Height 45mm, Mechanical Tube Length 160mm)

http://datasheets.globalspec.com/ps/522 ... 8971B858B5

When I saw Mr Chris S drawing................. I don't know.....?

Regards,

Conny
Last edited by conkar on Sat Mar 03, 2012 3:35 am, edited 1 time in total.

canonian
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Post by canonian »

Conny, I kinda hoped it's the other one:

Standard Achromatic Microscope Objectives -- MSO17900/100

EFL (mm): 8.2
Magnification: 20X (Long Working Distance)
NA: 0.30
Working Distance: 5.8
Specifications: DIN Type (Shoulder Height 45mm, Mechanical Tube Length 160mm)

http://datasheets.globalspec.com/ps/522 ... EB2467DEE7

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