Cheap LWD finite 20x objective for looking into 1mm of water

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

Moderators: rjlittlefield, ChrisR, Chris S., Pau

zzffnn
Posts: 1896
Joined: Thu May 22, 2014 1:25 pm
Location: Houston, Texas, USA
Contact:

Post by zzffnn »

Thank you Rik. Very very helpful!

When you said "Chris S.' objective", did you mean to refer to the eBay Nikon ELWD phase 20x objective that Chris S. mentioned previously? I am seriously considering that one, especially after reading your analysis! My only reservation now is that it is a phase objective and I heard that some phase objective do not work as well in bright field (some don't but some do -probably depending on implementation of the phase ring?).

I did run a very quick and dirty test with 1mm pond water layer and my eyes. 8x 0.2 or 9x 0.2 LOMO objectives look through 1mm of water without siginificant image degradation. With a LOMO 20x 0.4 and 1mm water, I did see some haze and shallow focus depth, but image is still decent under oblique gradient darkfield and contrast/resolution is still good (oblique gradient darkfield always enhances contrast greatly). But that poor 20x objective of mine have dipped into water many times due to its short working distance and sample isolation under it is a pain.
Selling my Canon FD 200mm F/2.8 lens

rjlittlefield
Site Admin
Posts: 23564
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Post by rjlittlefield »

zzffnn wrote:When you said "Chris S.' objective", did you mean to refer to the eBay Nikon ELWD phase 20x objective that Chris S. mentioned previously?
Yes, that one.
My only reservation now is that it is a phase objective and I heard that some phase objective do not work as well in bright field (some don't but some do -probably depending on implementation of the phase ring?).
I have no hands-on experience with phase objectives.

From theory, and from a posting several years ago by Charles Krebs, I expect that it would work about as well as non-phase in the plane of focus, but would have a sort of doughnut bokeh in OOF regions, rather like a mirror lens.

See HERE, in the third panel, phase top, brightfield bottom.

--Rik

zzffnn
Posts: 1896
Joined: Thu May 22, 2014 1:25 pm
Location: Houston, Texas, USA
Contact:

Post by zzffnn »

Thank you so much, Rik. I have seen that thread but somehow did not register it in my brain. Phase ring is not a concern then.
Selling my Canon FD 200mm F/2.8 lens

zzffnn
Posts: 1896
Joined: Thu May 22, 2014 1:25 pm
Location: Houston, Texas, USA
Contact:

Post by zzffnn »

Thank you very much everyone, especially Rik, Chris S. and Choronzon.

As discussed in the following thread, I purchased a "scratched" Nikon DLL (phase) 30x 0.55 objective for $30 and am very happy with it:
http://www.photomacrography.net/forum/v ... ht=#176981

This is an inverted objective from Nikon S series designed for cover slip thickness of 0.9-1.5 mm. Tube length is 160 mm and parfocal length is about 34 mm.

I am using it with oblique+gradient darkfield. Image quality is quite good given my application, certainly better than my LOMO (upright) 20x 0.4 objective. The Nikon has about double the working distance (about 3mm), more vibrant color, better resolution and contrast and slightly shorter body. No significant reduction of depth of focus under oblique+darkfield.

The "scratch" turned out to be only dirty or oil and it is only on the 0.17 correction shell, which I don't need.
Selling my Canon FD 200mm F/2.8 lens

Post Reply Previous topicNext topic