nikon M plan 20x 0.40 elwd - CA question

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jurkovicovic
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nikon M plan 20x 0.40 elwd - CA question

Post by jurkovicovic »

Hi all,

I have question about Nikon M plan 20 0.40 210/0 ELWD.
Is it normal, that objective has so much CA?
Does anyone have similary result? Maybe I´m doing something wrong. I used recomended extension, two flashes, diffuser.
Here is my result, stacked, unprocessed jepegs.
Thank you Filip
Image
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Macro_Cosmos
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Post by Macro_Cosmos »

I don't know about this specific lens but CA is pretty normal for objectives of this caliber.
1. This lens appears to be a finite objective with ELWD
2. It is not apochromatic
3. Due to the longer working distance, image quality is greatly compromised. Objectives with shorter working distances usually have higher NA ratings
4. Your lighting plays a role too. It's washed out from what I can see. Oh and light sources have "aberrations" too actually

I've seen people using the Mplan 10x lens with some success, magnifications beyond that aren't great according to someone I know who have used them.

A simple method would be to take photos of text printed on a piece of paper. Some people fill a shape black with 70% opacity or so, they look like singular splashes uniformly distributed when printed out and greatly magnified. I think we're gonna see pretty bad CA if you do so.

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Post by ChrisR »

Filip, sadly I suspect that's a poor example of the objective. They do vary. There are many bad ones.
I received one from China which rattled!

As MC says, it's a fairly old design which does show, in particular, Longitudinal CA. Photoshop's desaturation tool can be useful. So any image forming light from in front of, or behind, the focus plane will add unwanted colours. Therefore, the sharper you can get the in-focus parts, the better. Then the stacking program will exclude more of the OOF pixels.
Lowest ISO, small steps (what did you use)?) will make a difference. Also the lighting and its direction/degree of diffusion, and colour balance do make a difference in a sometimes-unpredictable way.

The LoCa effect is shown here, with this specific objective, which, nonetheless, Charles Krebs described as "one of my favorites".
( http://www.photomacrography.net/forum/v ... hp?p=19540 )
http://www.photomacrography.net/forum/u ... 6658_1.jpg

Charlie does get the sort of luck which results from vast amounts of work, but he has shown some remarkable images from this lens, eg:
from post at
( http://www.photomacrography.net/forum/v ... hp?p=29308 )
http://www.krebsmicro.com/forumpix/6716-6834Tufuse.jpg

As MC says, "ELWD" does come at a cost.
If you try the Nikon LWD and Normal versions from the same series which are still NA 0.4, but from the BD versions, an outer "shroud" unscrews leaving a very small exposed front element. These are much easier to get light around.
The NA is the same, so the angle of the cone of light into the lens is the same. There is a thin ring of metal around the front elements which negates that somehwat, but they can be cheap, and are worth playing with. (NB the mount is 26mm)

At 20x there's no nicely priced, excellent objective. The (infinite) Mitutoyo NA 0.42, is excellent - if you get a good one.
Also there Olympus models - but be careful l which one, and they aren't cheap.
Other than the Nikon BDs, an option is the Nikon finite "biological" 160mm 20x NA 0.5. It's designed for a coverslip and only has (iirc) 3mm WD which is no picnic, but the results are quite good without a coverslip. (Sometimes they're cheaper than current ebay item 163423162545).
Chris R

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Re: nikon M plan 20x 0.40 elwd - CA question

Post by dmillard »

jurkovicovic wrote:Hi all,

I have question about Nikon M plan 20 0.40 210/0 ELWD.
Is it normal, that objective has so much CA?
Does anyone have similary result?
Hello Filip,

Some CA is often seen with this objective, but nevertheless it is still capable of producing good results. I did a comparison test on here eons ago:

http://www.photomacrography.net/forum/v ... highlight=

and here's an image showing the objective's capabilities, albeit with considerable post-processing work:

http://www.photomacrography.net/forum/v ... highlight=

If you do a search you'll find numerous examples of excellent images from other members, mostly in the pre-Mitutoyo era.

Best regards,
David

I see Chris has already provided a very thorough answer while I was writing :wink:

jurkovicovic
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Post by jurkovicovic »

Ok guys, thanks for replyes. Not so good news for me. But I going to check posted links to find some next answers. If I have some next questions I will write. Thank you, Filip
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Macrero
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Post by Macrero »

That's a completely normal result for that objective and with that subject, given the high-contrast areas. Any finite Nikon achromat will show pretty serious CA, and ELWD versions are even more prone to aberrations, given the more complex optical design. The "CF" is just a marketing... Even the infinity achromats will show, not same, but quite similar CA in that area.

If you want a virtually aberrations-free objective, get a Mitty 20. The "modern" Oly's PlFL UIS and UIS2 are semi-apo (fluor) objectives, much better corrected than Nikon achros and can be found at a reasonable price.

Though you can get rid of the CA with a couple of clicks:

https://images2.imgbox.com/aa/b8/O4BiKWpj_o.jpg

Best,

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

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Post by rjlittlefield »

Macrero wrote:Though you can get rid of the CA with a couple of clicks:

https://images2.imgbox.com/aa/b8/O4BiKWpj_o.jpg
Impressive result.

Exactly which "couple of clicks" were those?

--Rik

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Post by Macrero »

Rik,

I just opened the image in PS, sent it to the ACR plugin/filter, then in "Lens correction" I adjusted the amount and tone to be corrected, and that's all...

Okay, there were more than a couple of clicks :lol: but it took me a few seconds.

https://images2.imgbox.com/b9/12/xrLnPVOa_o.jpg

Best and Happy New Year,

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

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Post by rjlittlefield »

Macrero wrote:just opened the image in PS, sent it to the ACR plugin/filter, then in "Lens correction" I adjusted the amount and tone to be corrected, and that's all...
Thanks for the details.

Yes, that method works very well in cases like this, where the false color from the CA does not also appear as natural color in the subject.

They are not common, but I have also seen impressive failures of this method in other cases, when the subject really did contain some of the same purplish hues that the CA contributed. I am thinking of a gray band along the edge of a purple flower petal, a problem that was initially reported to me as an unusual sort of halo. It was quite mysterious until we figured out that it was being caused by CA "correction".

--Rik

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Post by Lou Jost »

I often get those darn gray bands when using this method....

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Post by Macrero »

rjlittlefield wrote:Thanks for the details.

Yes, that method works very well in cases like this, where the false color from the CA does not also appear as natural color in the subject.

They are not common, but I have also seen impressive failures of this method in other cases, when the subject really did contain some of the same purplish hues that the CA contributed. I am thinking of a gray band along the edge of a purple flower petal, a problem that was initially reported to me as an unusual sort of halo. It was quite mysterious until we figured out that it was being caused by CA "correction".

--Rik
That's true. In this case it worked. It not always works flawless though. The grayish bands with this method are not that uncommon in my expirience, and are tough (or impossible) to fix. I'd rather spend some money on a well corrected objective... :P

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

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