Is this normal? (Nikon PA 20/0.75)

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

Moderators: rjlittlefield, ChrisR, Chris S., Pau

Macrero
Posts: 1166
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Is this normal? (Nikon PA 20/0.75)

Post by Macrero »

Playing with my Nikon Plan Apo 20/0.75 I noticed that when retracting the spring-loaded front lens the whole assembly is moving and the rear part comes out of the barrel.

Image

Can someone who owns this objective check if it behaves in the same way and report back? Thanks!

Best,

- Macrero
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Pau
Site Admin
Posts: 6051
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Yes, it is normal.
Pau

Macrero
Posts: 1166
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Thanks Pau! I am re-testing it without coverslip. Pretty usable after editing. Will post some test stack later on.
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Macro_Cosmos
Posts: 1511
Joined: Mon Jan 15, 2018 9:23 pm
Contact:

Post by Macro_Cosmos »

Incredible NA for a 20x. Easily feeds a 60MP sensor in theory. Looking forward to seeing the results

Macrero
Posts: 1166
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Yeah, 0.75 is impressive NA for this mag and I can live with 1mm WD. Unfortunately, the coverslip correction certainly and obviously affects IQ at that high NA.

This is a crop from a test stack with 150mm tube lens at 15X on sensor:

https://images2.imgbox.com/4c/1a/gEaLshyW_o.jpg

Did not come out well. Will try using shorter steps.
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Ichthyophthirius
Posts: 1152
Joined: Thu Mar 07, 2013 5:24 am

Post by Ichthyophthirius »

Hi,

There will always be spherical aberration without a coverglass. If you have the chance, experiment with a coverglass cap (small cap made from plastic tube to fit around the objective nose; coverglass glued to the plastic tube) and you might see an improvement.

Regards, Ichty

Pau
Site Admin
Posts: 6051
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Macrero, do you have many no cover glass 20X 0.4 like Nikon or Mitu industrial objectives?
If so I would like to see a side by side comparison to see if spherical aberration can kill the NA advantage of the PA 20/0.75
Pau

Macrero
Posts: 1166
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Ichty,

will try that, when I find the box with coverslips... :cry:

Pau,

many... no, actually I currently have only one no coverglass 20X - an Oly MPlanFl N 20/0.45. Well, a Nikon U20 too, but it is NA 0.33 only and is not a good reference objective.

From what I've seen in the few tests I shot with the Nikon, the NA penalty without coverglass is pretty significant.

Will make a comparison with the Oly tomorrow, though I am pretty sure it will (at least) match the resolution of the Nikon without coverglass and for sure will look better overall.
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Post by Scarodactyl »

I use mine to image inside gems. Once you get under the surface of a stone it usually behaves pretty well across a range of depths, but if you have anything reflecting on the surface (cracks, dust spots) they streak really badly across a stack. Still, it is an insane deal at 100bucks if there is any context you can use it in.

Lou Jost
Posts: 5942
Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

Post by Lou Jost »

If your subject supports it, you could also put a thin layer of oil over your subject. But risky for the objective if you hit the oil.

JKT
Posts: 420
Joined: Fri Oct 28, 2011 9:29 am
Location: Finland
Contact:

Post by JKT »

I was blown away by the sharpness and now I want the 10x version too. ;-)

The first test with Raynox DCR-150 & Canon EOS RP: http://jkt.1g.fi/Xtra/Blasto%20GP%20-%20large.jpg.
Corner vignetting is likely due to M42 connection on FF camera. That I have fixed.

The sharp image circle is limited, so much shorter tube lenses are not that useful. Longer ones should work well due to low resolution of the RP.

Considering my targets, the coverslip correction is just what the doctor ordered. :)

Pau
Site Admin
Posts: 6051
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Pau wrote:Macrero, do you have many no cover glass 20X 0.4 ...
Oops! I thinked that I wrote any, not many :roll:
Macrero wrote:Will make a comparison with the Oly tomorrow, though I am pretty sure it will (at least) match the resolution of the Nikon without coverglass and for sure will look better overall.
Please perform and post it
Pau

Macrero
Posts: 1166
Joined: Thu Sep 01, 2011 8:17 am
Location: Valladolid , Spain

Post by Macrero »

Lou,

I am afraid subjects won't get along with oil.

I had in mind Ichty's approach, and will try that once I find my coverslips...

Pau,

I was pretty optimistic saying that the Oly will just match the resolution of the Nikon without coverglass. It actually clearly outresolves it, and as expected, image looks much better overall.

Here is a quick comparison. Nikon with Apo-Gerogon 150 as tube lens, Oly with Componon 135. Shot in RAW, converted with same settings in Capture One 20. No additional adjustments/sharpening in PS.

Nikon:

https://images2.imgbox.com/a8/79/Eapf9Ior_o.jpg

Oly:

https://images2.imgbox.com/f1/f8/Ee96wWXc_o.jpg

Nikon with some levels adjusment and sharpening:

https://images2.imgbox.com/5d/50/VHgYGkxK_o.jpg

- Macrero
https://500px.com/macrero - Amateurs worry about equipment, Pros worry about money, Masters worry about Light

Pau
Site Admin
Posts: 6051
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Post by Pau »

Macrero, thank you very much for the test.
Of course I agree with your conclusion. Resolution is not bad but glare produces lots of apparent unsharpness. Another issue is the short WD conditioning illumination and likely also some scales out of focus
Pau

Macro_Cosmos
Posts: 1511
Joined: Mon Jan 15, 2018 9:23 pm
Contact:

Post by Macro_Cosmos »

Oly is the clear winner here despite the far lower NA. Nikon lacks the coverglass, not sure how well it will work with my slides for polarised light. Mine are all photographed at 10x, the 20x I use produces pretty poor results. Cover glass and polariser in the optical path, I guess it's too much for the 20x. Spherical aberration and the glare doesn't help resolution.

I had the chance to play with a zeiss water immersion objective lens, despite the high NA, without water it sucked. That's when I learnt that correct coverglass/immersion medium is crucial with these objectives. Your results are very helpful too.

First time I've seen scales like that, do you know the type of butterfly? If not, a wing segment phone pic should help. It looks incredible.

Post Reply Previous topicNext topic