Nikon CFI60 infinity-corrected objective and Raynox

[Craig Gerard]

Rik,

Thanks for the information regarding the MSN-202. Okay, you take 1000/diopter to get the result. I didn't know that, there is not much about numbers that I do know when it comes to calculations.

Here is a 100% crop of the '23'. This one was taken with the EF 70-200 @200 and CFI60 10X. The CA is not as pronounced as my initial observations, but it's there, to some degree, though probably insignificant for the most part.

I purchased this lense second/hand. The previous owner had flocked the inside of the lense hood and had also flocked the internal barrel between rear element and contacts, I took that as being a good sign.





Craig

[Bob^3]

Craig, thanks for doing all the hard work!

Your last image with the EF 70-200 at 200 looks very similar to what I’m seeing with the Nikon 200mm/4 AI. There is a small amount of blue-yellow CA at the edges of the D700 sensor, but well within simple removal level, in PS.

I've now positioned the Raynox DCR-250 40mm from the objective and added the CFI60 10X.

The image below is 160mm from sensor to objective shoulder.

I just want to confirm that in this set of images the distance from the Raynox to the objective is held at 40mm? So at the stated 160mm from sensor to objective shoulder in the 1st image, the distance from Sensor to Raynox is 160-40 = 120mm?

And in the second image (210mm from sensor to objective), the sensor to Raynox distance is 210-40 = 170mm?

It tells me one thing that may help when viewing/assessing the earlier images; my setup is still not level.

This is my main concern with the tests. Not only is the perpendicularity of the flat subject to the optical axis critical but also the fact that the optics are probably not providing a flat field to the sensor. Of course, one way around this is to perform a focus stack. But if you’re like me, you probably don’t like taking that much effort for a proof-of-concept test. A simpler option is to take just a few images that are each critically focused (using live view at max zoom) at various points from center to corner of the frame and looking at 100% (or higher) crops.

[Craig Gerard]

I just want to confirm that in this set of images the distance from the Raynox to the objective is held at 40mm? So at the stated 160mm from sensor to objective shoulder in the 1st image, the distance from Sensor to Raynox is 160-40 = 120mm?

And in the second image (210mm from sensor to objective), the sensor to Raynox distance is 210-40 = 170mm?

Correct. It's not where I would place the Raynox in future configerations; I didn't have enough adapters, etc, to position the Raynox in the appropriate location. This was a first-look project, but in the examples on page one of this thread, I believe the Raynox sufficiently demonstrates its suitability as a tubelense.

In future configerations, I'll have Rik's quote (below) printed in large letters and stuck on the wall behind my setup.

For best IQ, the Raynox must be mounted at one of its own focal lengths from the sensor, so that it focuses at infinity. It is separation between objective and Raynox that may change the image circle but not the IQ.

Also, some additional information using infinity-corrected objectives at link below: (worth pursuing)
http://www.photomacrography.net/forum/v ... php?t=9858

http://www.photomacrography.net/forum/v ... php?t=8995


Craig

[Craig Gerard]

I wish you luck with that part about "why".

When changing over to the EF 70-200 L USM, I neglected to set the focusing ring to infinity

Craig

[rjlittlefield]

When changing over to the EF 70-200 L USM, I neglected to set the focusing ring to infinity

Does this mean that with the ring set to infinity it works well? Or does that remain to be tested?

--Rik

[Craig Gerard]

Rik,

See image at top of page; but yes, I will be re-testing.

Craig

[Craig Gerard]

This item on eBay should prove useful when working with the various Raynox lenses. It should team well with my M42 focusing helicoid and allow me to position the Raynox in the appropriate position in the optics chain.

M42 screw 42 thread mount macro extension tube set (jinfinance)
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0246527130



Craig

[Craig Gerard]

Here's one more image taken yesterday using the Raynox DCR-250. This one has the CFI60 10X shoulder approximately 120mm from sensor.

Items used were Nikon PK-13, PK-12 extension tubes, a BR2A, a 52-58mm step-ring, a 2cm 58mm threaded extension tube, the universal adapter + Raynox, 49 to 52mm step ring and CFI adapter for the CFI60 10X. (*see notes below image)




* You can make the whole process less confusing by using a Nikon PB-4 bellows, a BR2A and appropriate adapters to couple the Raynox and CFI60 10X. The results are superb!

I'm playing with this arrangement now

If the Raynox lenses are not magic, then they are just very special indeed!

Here's one example.
Image can be improved (by paying more attention to focus ). I wanted to see the result, so this is a quick shot using the PB-4 and Raynox DCR-250 at approximately 140mm extension (sensor to shoulder)





Craig

[PauloM]

I don't know what that greenish tint is on the right side?

If you tilt the graduated slide a little, do you get more green in the parts that are further away than the plane of sharpest focus, and magenta in the parts that are closer?

Hi Chris,

I have had this happen on occasion, while shooting test images of an exposed EEPROM (Integrated Circuit, so lots of reflecting surfaces).

What would this be a symptom of?

Cheers,
P

[ChrisLilley]

What would this be a symptom of?

Axial (longitudinal) chromatic aberration, which is a dependance of the focal length on wavelength. More specifically, the green and purple colouring is symptomatic of an achromatic lens.

Achromats have a focus vs. wavelength plot which is a curve, two wavelengths can be in focus simultaneously. This means that violet and blue wavelengths are at one side of the zero point, greens on the other side, and oranges and reds back on the same side as violet and blue. As a result, out of focus areas further than the plane of focus are green, typically a characteristic emerald green, while areas out of focus closer than the plane of focus have a magenta or purple colour.


Image credit: Paul van Walree.

For further information:
Chromatic Aberration, by Paul van Walree
Lens Aberrations, Georgia State University
Defining apochromatism, by Thomas M. Back

[ChrisLilley]

Also, the reason this is most clearly seen at high contrast transitions, such as specular highlights or strongly backlit subjects, is that the intensity of the out of focus secondary spectrum directly depends on the intensity of the light. Imagine a point light source. At the wavelengths where focus is exact, it will resolve as a point (1). At the wavelengths were is is most out of focus, it will resolve as a disk (2).

For objects a little behind the plane of focus, at most wavelengths they are out of focus but in the green area of the spectrum, the light is still in focus giving a very visible green colour.

For objects a little in front of the plane of focus, at most wavelengths they are out of focus but in the violet, blue, orange and red areas of the spectrum, the light is still in focus giving a still fairly visible, though less saturated, magenta colour.

At greater distances, more complex effects are seen (purple with green edges, green with purple edges, etc)

If an out of focus coloured area from a bright source, falls onto a photosite where the in-focus image is black or dark, it will contribute a lot to the eventual reproduced colour. if it falls on a bright area, it just mixes in as a small colour shift.

(1) ok it will resolve as an airy disk. Lets treat tha tas a point, especially if it spans less than one photosite.
(2) the airy disk has a significantly larger radius, spanning multiple photosites.

[PauloM]

More specifically, the green and purple colouring is symptomatic of an achromatic lens.

So these fringes are to be expected from a Plan achromatic objective, like those from the Nikon CF Plan series, and all we users can do is try to minimize their effect by reducing (or preferably, eliminating) specular highlights and other fringe-inducing OOF reflections.

Did I interpret your explanation correctly?

Cheers,
P

[Joaquim F.]

Chris,

When using the Raynox with the focusing helicoid it focuses on infinity at approx 125mm from the sensor. The resulting image is soft, as you would expect; but it's an image nonetheless.

Craig


*edit: typo

Hi, in my initial setup with cf plan 10X and the raynox lens:

http://www.photomacrography.net/forum/v ... php?t=9906

the last work better inverted, with its infinity side forward capturing the "infinity image" projected by the nikon cfi, focusing on something distant with just the raynox lens mounted in the bellows you can view quickly that it gives better quality in that way.
The nikon PB-6 bellows have a very convenient rear 52mm screw in the frontal mount for that configuration, I think some Olympus and Pentax bellows have similar mounting screws originaly intended for mounting reversed lens or accesories.
The raynox image still have low contrast but is chromatically very clean and together with the cfi objective and with 10 cms or so of separation between the two lenses the resulting image is very good.
The raynox dcr-150 is very close in focal and luminosity at original Nikon tube lens and I think is the best "clon" of that lens.

greetings

Joaquim

[ChrisLilley]

More specifically, the green and purple colouring is symptomatic of an achromatic lens.

So these fringes are to be expected from a Plan achromatic objective, like those from the Nikon CF Plan series, and all we users can do is try to minimize their effect by reducing (or preferably, eliminating) specular highlights and other fringe-inducing OOF reflections.

Did I interpret your explanation correctly?

Cheers,
P

Mostly.

Achromatic lenses all have a curve with two crossings of the zero line. Where they differ is in the flatness or steepness of the curve. A poorly corrected lens has a deep curve, the area under the curve is large and the amount of secondary spectrum is significant. A well corrected lens has a flatter curve, a smaller area under the curve, and much less noticeable secondary spectrum.

So, some lens designs are worse than others in this regard.

Apochromatic designs do better, with three crossings (plus the correction of spherical aberrations between two widely spaced wavelengths) and thus tend to have much purer colour. And tend to be much more expensive.

[PauloM]

(...)
And tend to be much more expensive.

Thank you for your clear explanation.

Cheers,
P