Telecentric Scanner-Nikkor ED LENS: Nikon 8000 ED lens

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RDolz
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Post by RDolz »

etalon wrote:Hello Ramon,
I have one more question concerning your setup: As I saw on your picture, you use the scanner nikkor 8000 in reversed mode (like Robert in his setup, too). Is there any advantage in reversed mode vs normal orientation? Have you ever tried the lens in normal orientation?
Hi Markus, I was finally able to capture the images with the Coolscan 8000 in telecentric mode, with a diaphragm whose diameter is 9mm and with a FOV of 16.33 mm. Zerene mode DMap without scale.

The Coolscan is asymmetric and the diameter of the outer lenses have a different diameter. The best quality I get with the larger lens oriented towards the subject and the smaller lens oriented towards the sensor. It is the position that I show in the initial image of this post. I explain this because I do not know how it was originally mounted in the scanner.

I have photographed a silicon wafer,

Image

Next, comparative details of the center, the right side and the top right corner.

Image

the right side

Image

and the top right corner.

Image

As you will see in the center, the quality is very similar, but there is a significant difference on the sides.
etalon wrote:Would there also be an atvantage in reverse mode, if I use that lens not in telecentric mode?
Although it is not so pronounced, the same thing happens without the iris to convert the lens into telecentric.

My lens seems to be in perfect condition, ... but I would love to be able to compare this with other lenses: can someone repeat this test?
Ramón Dolz

Lou Jost
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Post by Lou Jost »

I wish I had photographed the lens in the scanner before I took it out. But the measurements I made and reported above should be sufficient. Use those measurements for best results; try the lens both ways using those distances (remember they are +/- a few millimeters) and see which is best.

jcb
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Post by jcb »

The part made of 3 rings is the sensor side in the scanner, the part made of 2 is the film side.
If you want to see a picture, there is one lens assembly for sale on ebay (item 153325792071). The sensor is on the short side of the plastic carrier part.

RDolz
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Post by RDolz »

jcb wrote:The part made of 3 rings is the sensor side in the scanner, the part made of 2 is the film side.
Jcb, thanks for the information.
Lou Jost wrote:I wish I had photographed the lens in the scanner before I took it out. But the measurements I made and reported above should be sufficient. Use those measurements for best results; try the lens both ways using those distances (remember they are +/- a few millimeters) and see which is best.
Lou, keep in mind that to convert the coolscan into telecentric, with an iris, the position occupied by the iris is the point that makes the rays of light are parallel on the face of the object to be photographed.

As you know, I determine that position with an optical system focused at infinity, looking through the lens from the position where the object to be photographed will be.

At the moment in which the perfectly focused iris is observed, that is the position in which the telecentricity is obtained. With small variations of this position the iris looks out of focus.

Therefore the distance between the back of the Coolscan lens and the iris is determined very precisely and, in my opinion, it is immovable if you want to obtain the best possible telecentricity.

I have made this adjustment in the two directions tested.

Although I have not measured it, and given that the lens is asymmetrical, I believe that the distance between the back of the lens and the iris will be different depending on the direction in which the lens is mounted.

The only thing that I modify, once the iris is fixed, is the distance from the iris to the camera's sensor to get more or less magnification.

best regards.
Ramón Dolz

Lou Jost
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Post by Lou Jost »

Yes, my data ignores the telecentricity, but I was speaking about the distances that the lens was designed for, in its ordinary configuration.

RDolz
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Post by RDolz »

Lou Jost wrote:Yes, my data ignores the telecentricity, but I was speaking about the distances that the lens was designed for, in its ordinary configuration.
Lou, please, can you summarize what would be the best configuration, including increases and distances, to use the Coolscan 8000 in ordinary mode ?.
etalon wrote: I have a Nikon coolscan 4000 lens, and I found, that the pics would be better in normal orientation. But that is only my opinion and I can't proof it...
Markus
I remembered that I did a test with the Coolscan 4000 in telecentric mode, in both directions, and that I had the test images. Depending on the direction in which you use it, as I mentioned earlier that would happen for the Coolscan 8000, the diaphragm is at different distances from the back of the lens. Once determined these distances, approximately, in 22 mm and 14 mm. I'm sorry, but I can not tell which direction these distances correspond to.

A matrix printed on paper, a FOV of 11.1 mm (2.1X), and the telecentric diaphragm with a diameter of 6.25 mm.

It also happens the same as for the 8000, in telecentric mode one direction is much better than the other. In addition, in both images, a vignetting effect appears (which as Rik explained has to do with the loss of quality of the telecentricity in the edges of the image).

The best image quality corresponds to the position in which the diaphragm is 14mm from the back of the lens.

Here you have a summary. In the upper part the center of the image, then the right side and finally the upper right corner.

Image
Ramón Dolz

Lou Jost
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Post by Lou Jost »

Ramon, the distances I gave above are the best I can do, at this point. These must be the distances that the lens is optimized for.

etalon
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Post by etalon »

Hello gents,

Ramon, thank you very much for the pics! Well, since I don‘t do stiching, I don‘t need the telecentric mode. I will use it for high res imaging at 1:1. Because the optic is designed for a magnification near 1:1, I was wondering, why some people use the lens in reversed mode. My thought was, that the manufacturer use the developed lens in the best manner for his purposes...

JCB, are you sure? Following the last pic on Roberts homepage https://www.closeuphotography.com/how-t ... 00-scanner
it looks to me, as the part with the two rings are the sensor side. This is, why I‘m asking for any improofment using the lens in reversed mode.

Thank you all for your answers. When I got my lens, I‘ll do some tests as well...

Cheers,
Markus

etalon
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Post by etalon »

Ramon,
I remembered that I did a test with the Coolscan 4000 in telecentric mode, in both directions, and that I had the test images. Depending on the direction in which you use it, as I mentioned earlier that would happen for the Coolscan 8000, the diaphragm is at different distances from the back of the lens. Once determined these distances, approximately, in 22 mm and 14 mm. I'm sorry, but I can not tell which direction these distances correspond to.
This distances should be the focal length of that lens for each side. If you look through that lens with an telescope focused at infinity, and put the iris diaphragm at the point behind the lens, where you can see it sharp, than should that be the nominal focal length of that side of the lens...

Cheers,
Markus

P.S. The 4000 lens have a paint dot at one side on the barrel. This is the side, which is pointing to the sensor (original orientation). I don‘t know, whether the 8000 lens have also that paint dot (but I think so). This should also be the side pointing toward the sensor in original application...

Olaf G
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Post by Olaf G »

etalon wrote:P.S. The 4000 lens have a paint dot at one side on the barrel. This is the side, which is pointing to the sensor (original orientation). I don‘t know, whether the 8000 lens have also that paint dot (but I think so). This should also be the side pointing toward the sensor in original application...
It is the same with the LS-8000 lens.

You can see on the pictures that the "long" side of the lens made with 3 rings points towards the mirror (i.e. the film) which is located on the short side of the carrier.

http://www.shtengel.com/gleb/Nikon_8000 ... eaning.htm
https://www.closeuphotography.com/how-t ... 00-scanner

I do use both lenses (LS-40 and LS-8000) on a Sony A7 with the paint dot towards the sensor and they give me excellent performance at their intended magnification:
1.33x for the LS-40 (24mm film projected on a 32mm sensor)
0.9x for the LS-8000 (63.5mm film projected on a 57.5mm sensor)

See also here:
http://www.savazzi.net/photography/scan ... 100mm.html
http://www.savazzi.net/photography/scan ... _40mm.html

P.S.: The LS-8000 might be excellent reversed as well (haven't tried that yet). For the LS-40/4000/5000 it is definitely not recommended (at least on full frame).

RDolz
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Post by RDolz »

Olaf, thank you very much for the clarification ... this confirms that, in telecentric mode and although I can not explain it, I get the best quality of the Coolscan 8000 in reverse mode with respect to its original position in the scanners: the paint dot (two rings) towards the subject.
Ramón Dolz

Olaf G
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Post by Olaf G »

RDolz wrote:Olaf, thank you very much for the clarification ... this confirms that, in telecentric mode and although I can not explain it, I get the best quality of the Coolscan 8000 in reverse mode with respect to its original position in the scanners: the paint dot (two rings) towards the subject.
Maybe because of your magnification of 1.12x where I would expect the reversed lens to perform very well. In the intended direction (best at 0.9x) the image quality suffers already...

RDolz
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Post by RDolz »

Olaf, maybe you're right because with a higher magnification of 0.9X, in my tests and in non-telecentric mode, I also worked slightly better in reverse mode.

When I have time, I will do the tests in a non-telecentric mode at the nominal magnification and at the nearby ones.
Ramón Dolz

etalon
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Post by etalon »

Hi at all,

What I‘m really wondering about is, that, if the lens is used in design magnification (around 1x), there are many different experiences by the user of that 8000 lens concerning the mounting direction. Normally the developer and manufacturer of that lens should use it in the best way, to get the best results with that lens, because he has designed it for his purposes.
How can it be, that there are better results visible to some user by using it reversed?

Cheers
Markus

Lou Jost
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Post by Lou Jost »

The two magnifications being discussed here, 0.9x and 1.12x, are very close but are on opposite sides of the 1:1 mark, so it makes sense that the best orientation for 0.9x is the reverse of the best orientation at 1.12x.

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