Problem in first use of Nikon infinite lens (10x)

crystalline · Post by **crystalline** » Wed Feb 01, 2017 11:54 am

Hello Everybody,

It's my first message in the forum, so I hope everything will go smoothly :-)

First of all thank you all for this amazing forum, where we can learn so many things about photomacrography and e-meet nice people with a lot of good will to help.

I make photos of minerals and crystals since 2013 and use a microscope lens the last thee years. So far, I had only a Carl Zeiss 25 mm used with bellows and a Canon 5D MkII with external Canon flash. I was quite happy with the results (three photos below; more in mindat.org), but was always admiring the sharpness of photos of people who used better lenses or more sophisticated rigs.

I recently read several posts regarding infinity lenses in the forum and all about the method of Ploum (see:
http://www.photomacrography.net/forum/v ... ight=ploum
and
http://www.photomacrography.net/forum/v ... ight=ploum )

that I wish to apply soon. Waiting for all the ordered necessary pieces to arrive, I decided to test my recently bought Nikon CF Plan 10x 0.30 ELWD (new from e-bay) in a conventional (compared to Ploum's) vertical set-up. I used a reversed Raynox 250mm as tube lens at the focal distance of 12.5 cm from the sensor and the Nikon lens as close as possible to the tube lens (I also tried at other distances like 20 cm etc. with identically poor results). I hope all is visible in the two photos below.

The results were very disappointing even when I locked my mirror or tried IKEA led light. The system seem not being able to really focus at any point. I started wondering if the problem could be the reversed Raynox. I never understood why it should be reversed (I cannot understand how it can work positioned normally, but also reversed???), but since experienced people use it like this and apparently have better results, I did not try so far to make this change. Below I upload a photo of a ruler and a cropped detail with the above described system:

No photo-stacking has been applied. Among several shots (with stackshot) I uploaded the best focused photo. (photos of minerals were also of very poor quality)

Can you please help me understand what I am doing wrong and cannot get at least as good results as with my old Carl Zeiss 25 mm, if not much better?

What kind of extra tests could i make to locate the problem?

Thanks in advance!

harisA · Post by **harisA** » Thu Feb 02, 2017 6:06 am

kalos irthes sto forum-Welcome to the forum.

Although i don't have experience with your nikon microscope objective (this is an old series infinity objective) i have some points.

1)You are using a full frame camera.It is very optimistic to expect a full sensor coverage from a microscope objective.With the exception of mitutoyos the majority of them will only cover a 20-27 mm image circle.
2)If i understand correctly you are using a raynox DCR-250.tHIS is an 8 dioptries 125mm focal length lens.Your objective needs a 200mm tube lens.Using a lens with lower focal distance will give you a smaller image circle and a lower magnification.Raynox DCR-150 will be better in your case.

harisA · Post by **harisA** » Thu Feb 02, 2017 6:07 am

I tried to welcome you in Greek but the forum is not accepting Greek characters.

crystalline · Post by **crystalline** » Thu Feb 02, 2017 9:56 am

Efcharisto poly! harisA - Thanks a lot! (also for your Greek welcome)

Fortunately, I do have Raynox DCR-150 as well, so I will try to follow what you proposed asap. So far, I was (wrongly) thinking that tube lens' length (=distance from the sensor) depends only on the tube lens' focal length (e.g. 125mm for Raynox DCR-250 and 200mm for Raynox DCR-150).

I am happy that I learned something

and hope it will work with my infinity lens.

Do you know if the same focal distance (i.e. 200 mm) will be fine also for my second infinity lens Nikon CF Plan 50x 0.55 ELWD, WD 8.7mm?

Best wishes

harisA · Post by **harisA** » Thu Feb 02, 2017 10:38 am

In order to find the proper distance between tube lens and camera sensor you have to do the following:
Remove the objective and point the camera with the raynox attached to an open window (raynox must be reversed).
Try to focus to a distant object (several hundred meters away).When the object is in focus lock the position and put the objective back in place.
In general with thin tube lenses (like raynox) the distance between sensor and tube lens is aprox . the focal length of the lens.
yes the 50x objective requires the same tube lens

crystalline · Post by **crystalline** » Thu Feb 09, 2017 5:04 pm

Following the instructions of harisA (thanks a lot!) I focused the tube lens pointing at objects some 2000 m away.

It seems to me (but I may be wrong?) that there was a difference, while taking a photo of the same ruler that I presented above. Some fine details of the ruler's surface seem to become visible and focused.

RULER AFTER FOCUSING TUBE LENS

However, there was no visible difference when I tried to photograph a crystal. Below photos of similar crystals (with photostacking) before and after properly adjusting the distance between sensor and tube lens.

BEFORE

AFTER

Then I also added an Iris between the objective and the tube lens (reversed Raynox DCR-150).

AFTER IRIS

The iris seems to significantly improve the results. However, I have the feeling that I am still very far away from the sharpness and clarity of photos of people working with the same kind of infinite lenses (Nikon x10 or x20) and tube lenses. You can compare with photos of Ploum in the following link:
http://www.photomacrography.net/forum/v ... ight=ploum

Can you please help me by proposing some tests that I could make in order to find what I am not doing correctly, in order to achieve similar results?

ChrisR · Post by **ChrisR** » Sun Feb 19, 2017 8:17 am

I wonder if you have made any discoveries, Alexadros?

Al I could suggest is to try a fiendly subject such as laser printed white paper, to test for it being a faulty objective. Obviously you don't want to be reducing the aperture.
Do you have a distance (try perhaps 50-100mm) between the tube lens and the objective?

crystalline · Post by **crystalline** » Tue Feb 21, 2017 2:16 pm

Thanks a lot ChrisR.

No progress so far

, but harisA kindly proposed to test the lenses in his microscope (since we live in the same town)

. We will do so during the very next days hopefully and I will let the forum know. I bought the lens as "new" through e-bay from the US and seems perfect externally and at both glass ends... I want to buy a Mitutoyo 20x, but if it shows up that I had the traumatic experience of faulty e-bay Nikon lenses, I will think better buying one new from Mitutoyo directly (if I ever manage to gather the huge amount of money needed...)

Regarding the distance, it was about 15 mm before adding the Iris and it is about 25 mm now. Does this distance play a role? I have read that I should keep it to the minimum possible...

Pau · Post by **Pau** » Tue Feb 21, 2017 4:00 pm

I have this very same objective and it is very sharp (it suffers of pretty strong longitudinal CA but it disappears when stacking)

abpho · Post by **abpho** » Tue Feb 21, 2017 7:29 pm

I feel your pain Crystalline.

crystalline · Post by **crystalline** » Fri Feb 24, 2017 3:39 pm

The funny news are that both my Nikon lenses (x10, x50) are fine after being tested in the microscope of harisA (thanks harisA!). These are the good news...

The bad news are that the mystery goes on... Why I cannot get clear and sharp photos?

I took off the camera and looked inside the tube while using 4 IKEA leds to illuminate the subject. I do not know if it is normal, but I saw reflections in two areas of the tube (by naked eye). This should not happen, since I am using expensive NOVOFLEX bellows. Anyway, I observed (always by naked eye) that the reflections disappear when I close further down the iris. So I have one more think to check now...

I am afraid this won't be the solution, but I will give it a try and will come back with the results.

johan · Post by **johan** » Sat Feb 25, 2017 1:25 pm

Are you using Jansjo for lighting?

crystalline · Post by **crystalline** » Sun Feb 26, 2017 9:06 am

Pau can you please let me know with what tube lens (Raynox as me or something else) and length (~200 mm?) are you getting the sharp results?

johan I usually (almost always) use my Canon flash, but while preparing the stage (while in live view) and in the tests that I am doing now with the Nikon 10x I use 4 Jansjo as fixed light. I read that several photographers of the forum use them also for their final shots. Some make excellent photos. To me they seem too yellowish.

I tried to make the same test photo with my old Carl-Zeiss Luminar 25 and my new Nikon x10 (that I still cannot use properly...). I think the problem is obvious here as well. Several details disappear completely with the Nikon and there is this diffuse light, like if we can never focus correctly.

I used the 4 Jansjo LED lights for these shots.

Any comment about what may be going wrong with the Nikon is very welcome.

Pau · Post by **Pau** » Sun Feb 26, 2017 9:33 am

I used it with the Canon EF70-200 f4 IS USM as tube lens but the problem likely is not the tube lens (if rightly used), likely it will be due to a defective objective. My 10X is sharp and resolution is better than the venerable Luminar 25X I also own pushed at 10X but I had a bad experience with a 50X from the same series that despite looking as new was unusable

ChrisR · Post by **ChrisR** » Sun Feb 26, 2017 10:25 am

Was that with the iris still stopped down?

Nikon Bellows need some flocking too, if it's any comfort!

Shiny adapters are often a severe problem.