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Zeiss Luminar's light problems

Posted by Matteo Chinellato  
avatar
Matteo Chinellato January 04, 2008 09:40PM
when I use the Zeiss Luminar 16 mm and 25 mm in some photos of micro crystals the image appear with a visible grain. It is a problem of light? If I use optic fibers this problem vanishes?
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dominik schlaefli January 04, 2008 09:53PM
Could you post a photo of the "grain" ? It could be due to diffraction (use a diffuse source) or to amplified detector noise (force the camera to work at lowest ISO setting (ISO 100 or less) and increase illumination level or exposure duration).
kind regards,
Dominik.
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Matteo Chinellato January 04, 2008 10:04PM
here a horrible example of photo not polished with the 16 mm. use 100 iso setting in mu Canon 20d


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dominik schlaefli January 04, 2008 10:29PM
OK, so it's not what I was expecting. I don't see any "grain". In the background there seem to be some slight compression or stacking artefacts. There's some dust on the subject, and there are the trails of sensor dust due to the stacking. From their radial pattern, it looks like magnification varies between the stacked images, which is odd. Could the lens be drifting with respect to the camera body in your setup? If this is done with helicon focus, as i suspect, try the dust mask feature (uses a uniform gray photo to identify camera dust). With CZ, the blurred background will look smoother.
kind regards,
Dominik
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Matteo Chinellato January 05, 2008 05:21AM
Could the lens be drifting with respect to the camera body in your setup

I use the Zeiss mounted in a Nikon bellow. I know he have the dust on the camera, but in the micro minerals the photo does not appear clear, it is like out of focus
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dominik schlaefli January 05, 2008 12:31PM
What's the field of view of the photo you posted ? The lack of sharpness is probably due to the limit in resolving power of the lens. If you are already working with the iris fully open, there's not much you can do.
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Matteo Chinellato January 05, 2008 12:38PM
its many few, calculate the anatase is a 0.8 mm crystal, in total is at 3 mm area
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dominik schlaefli January 06, 2008 01:24PM
Based on the luminar 16 NA of 0.2, one would expect it to resolve ca. 1.5 um, a 3mm field of view should look sharp on a picture 1000 to 2000 pixels wide (depending on what you consider "sharp"). There's a problem somewhere, but it's not the lighting. You need to find whats wrong with the your optical system. I'd suggest doing some photos of a target inclined at 45° with respect to the optical axis of your system, to see where your focal plane is, how deep the field is, and if magnification varies strongly along the axis.
kind regards,
Dominik
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Don Saathoff January 06, 2008 10:43PM
I feel I see movement of some sort. Look at how you are focusing for multiple exposures for stacking, look at how smooth the movements are in the setup, be sure a remote shutter release is used (either cable, electronic, or delayed release). The movements of the artifacts produced by the stacking are almost s-curved and the highlights on the xl show slight directional un-sharpness.

Don S.
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dominik schlaefli January 07, 2008 06:21PM
If you haven't already, you could also try mirror lock-up (flips the mirror 2 s before opening the shutter).
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Matteo Chinellato January 07, 2008 07:12PM
hard this with a digital type the canon 20D and with several exposure for helicon
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Jean-Marc Johannet January 07, 2008 07:23PM
OK Matteo, but please if Canon 20D allows you to do this, just try one shoot to see if the problem could come from mirror movement vibrations.



Edited 1 time(s). Last edit at 01/07/2008 07:24PM by Jean-Marc Johannet.
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Matteo Chinellato January 07, 2008 09:06PM
this is a single shoot to a anatase of 0.8 mm. not polished, not change colors etc...


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Douglas Merson January 08, 2008 05:34AM
It would appear that the optics/sensor need cleaning to get rid of the dark spots in the image.
Doug
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Matteo Chinellato January 08, 2008 06:15AM
I have clear few months ago but in few days return the same.
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Don Saathoff January 08, 2008 08:20PM
Matteo....you say the anatase was a single exposure or did I mis-understand you? If not multiple stacked exposures it's really confusing because the artifacts (black spots) show, at magnification, movement in an upper left - lower right direction but I don't see that movement in the highlights of the image (which would be the case is stacked...just over-all lack of sharpness when the software can't find anything sharper).

If no movement, the problem is focus or lens. Some basic questions: do you focus w/ your glases on or off....does your camera have a diopter adjustment for individual eyesight anomolies....has the lens been dropped (loose elements)
.....are you shooting at the lens' optimum aperture (the old rule was "one stop down from the middle")
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Jean-Marc Johannet January 08, 2008 08:27PM
Does your adaptator between bellows and your Canon 20D body have a lens inside?
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Matteo Chinellato January 08, 2008 08:29PM
hard to explain in english. The first photo I have put is with Helicon, the last of the blue anatase is a unique shot. The Zeiss Luminar is 98% new, mounted on Nikon bellow and use for all photos a f8. Calculate with normaly Canon lens type a 100 mm I not have any problem, the same if I use the Zeiss 63 mm
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Matteo Chinellato January 08, 2008 08:32PM
Does your adaptator between bellows and your Canon 20D body have a lens inside?

no any lens. You seen my set here

http://www.mindat.org/mesg-13-51471.html

last photos
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dominik schlaefli January 08, 2008 08:52PM
Is f8 the maximum aperture ? you should open it fully for maximum resolving power. Depth of field is taken care of by the stacking SW.
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Matteo Chinellato January 08, 2008 08:56PM
no I have in the 25 mm the f15 max in others I arrive to F30, but up the f10 the image lose many quality.
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Jean-Marc Johannet January 08, 2008 09:13PM
Matteo,
I think there is not fx stops on Luminars but only numbers: 1,2,4,8 & 15.
First number (1) is for fully opened aperture.
Between two numbers 50% more of time is need to have the same result.
If you use it at 8, it is nearly fully closed and your will need very long expossure time, subject to unfocus if your set is not stable enough!!

Did you make your tries with long extension on you bellows or short one?
Luminar 16 mm is given for very high magnifications, you have to use it at his optimum ratio, 14:1.

Jean-Marc.



Edited 1 time(s). Last edit at 01/08/2008 09:17PM by Jean-Marc Johannet.
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Don Saathoff January 08, 2008 09:14PM
Matteo, I've been in photography for over 40 years, mostly as an engineer....but, I'm completely baffled by your problem. Digital is new to me but some aspects of photography are simply universal and subject to the same physical laws. In the anatase xl alone I simply see a sharpness or focus problem, but the "moving artifacts" are beyond me.

I see nothing in your set-up out of the ordinary. Does your camera view-finder use a ground-glass focusing screen w/ the image projected directly to the ground-glass or are you focusing on an image produced by an LCD? If there is a true ground-glass, are there any grid marks or indexing lines in the ground-glass and, if so, do they appear sharp to your eye? Also, if using a ground-glass, is your reflex mirror re-seating all the way down?

If you are seeing the image as sharp in the viewfinder, then the relationship betweem the projected image on the film (CCD) and the relationship between the projected image on the focusing medium is different. If the image you see in the viewfinder is sharp then I would suspect a mechanical problem in the camera!

Don S.

Jean-Marc was posting while I was writing this book...he has a point...stopped all the way down is NOT the optimum aperture!....and I assume you set aperture AFTER you focus wide open.



Edited 2 time(s). Last edit at 01/08/2008 09:19PM by Don Saathoff.
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Matteo Chinellato January 08, 2008 09:38PM
Matteo,
I think there is not fx stops on Luminars but only numbers: 1,2,4,8 & 15.
First number (1) is for fully opened aperture.

yes, and the photo is not complete focus

Between two numbers 50% more of time is need to have the same result.
If you use it at 8, it is nearly fully closed and your will need very long expossure time, subject to unfocus if your set is not stable enough!!

depend on mineral, normaly I have a 1 to 4 sec. of exposure if is put on 8, if I put on 4 I not have a image unfocus

Did you make your tries with long extension on you bellows or short one?

depend if i want have a high expansion or not, normaly I fix the front and I go on and down with the leaves back where I have the camera

Luminar 16 mm is given for very high magnifications, you have to use it at his optimum ratio, 14:1.

not like many the 16 mm, not give a well focus photo
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Matteo Chinellato January 08, 2008 09:44PM
Matteo, I've been in photography for over 40 years, mostly as an engineer....but, I'm completely baffled by your problem. Digital is new to me but some aspects of photography are simply universal and subject to the same physical laws. In the anatase xl alone I simply see a sharpness or focus problem, but the "moving artifacts" are beyond me.

I see nothing in your set-up out of the ordinary. Does your camera view-finder use a ground-glass focusing screen w/ the image projected directly to the ground-glass or are you focusing on an image produced by an LCD?

direct from viewfinder of the camera, is for this I want change the camera for have a live view on the camera monitor

If there is a true ground-glass, are there any grid marks or indexing lines in the ground-glass and, if so, do they appear sharp to your eye? Also, if using a ground-glass, is your reflex mirror re-seating all the way down?

If you are seeing the image as sharp in the viewfinder, then the relationship betweem the projected image on the film (CCD) and the relationship between the projected image on the focusing medium is different. If the image you see in the viewfinder is sharp then I would suspect a mechanical problem in the camera!

The camera have reviewed 4 months ago and all is ok have say who have control,probably I have to change the camera seen in 1 year is go over the 50.000 clicks

Don S.

Jean-Marc was posting while I was writing this book...he has a point...stopped all the way down is NOT the optimum aperture!....and I assume you set aperture AFTER you focus wide open.

no, I set the aperure first to focus and it remains fixed for all photo session
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Don Saathoff January 09, 2008 12:58AM
Matteo....I give up....I surrender....I have no more ideas for you....I am really sorry!!!

Don S.

WAIT!!!...try focusing wide open THEN stopping down....when you focus at a smaller aperture, the "circle of confusion" is smaller and depth of field will prevent a sharp focus (what you percieve as being acceptably sharp could actually lay anywhere within that depth of field distance)...focus wide-open THEN stop down for exposure!!!
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Robert Simonoff December 30, 2010 02:02AM
Matteo did you eve find a "resolution" to your problem. I have seen many fine micro photos from you, but are they using this setup?

Thanks
Bob
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Fred Kruijen January 09, 2011 07:35PM
Ciao Matteo,

Some (top) lenses are made to use them with the aperture fully opened. I see no reason why you should stop down.
I suggest to focus wide-open, and don't stop down for exposure.

Distinti saluti,
Alfredo.
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Matteo Chinellato January 09, 2011 08:51PM
hello

normaly I use the zeiss 16 mm at the 4.5 close, if I use all open the image lost many on the borders

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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Volker Betz January 09, 2011 10:12PM
Hello Matteo,

I have seen this thread before, but as am working on that subject my answer is a little late.

I see some movements in your picture, coming from your setup with bellows on a tripod. I would recommend to mount your bellows on a more vibration free stand.

To avoid that you need a more compact and more stable installation. Your set up is fine with the 63 mm Luminar. I was running in the same problems with the 25 mm range lenses and a Canon 500 D. Even with mirror lookup the pictures with 25 mm Luminars suffered of sharpness compared to such I made with a 4500 Nikon ( and ocular adapter).

In the end now use a (very old) Ortholux Microscope with my Luminars and Photars in the 25 mm range. This is a 9 kg stand, very solid. Also the bellows are not perfect for the small fields of view, I would prefer fixed tubes.

Also the bajonet connection between camera and bellows has often to much room for movement. I saw significant improvements if the camera and the bellows are connected to the same base and not only the camera at the bellows. (not easy to to, by the way.)

Recent experiments showed me that any kind of shutter is not good for small fields of view. I am just making experiments with a Panasonic D2. It has no mirror and a different shutter: But even with that camera there is some loss of sharpness at short exposure time. But long exposure time helps. I could document that there is a significant difference between a 1/125 sec. and a 2 sec. exposure. 2 sec. a much sharper. I could measure a 1.5 micron resolution using a 15 mm Mikrotar of N/A 0.2.

A DSLR is not the best for small fields of view, the best would possibly be a cooled heigh resolution microscope camera (in theory) but this are horrible expensive. So the micro 4/3 cameras used with a about 2 sec. exposure seems to be the a reasonable solution at present, until we get a 12 Mpixel video camera which is very questionable.



Another point is that you close the aperture. This is not advisable for a 25 mm luminar. I made some experiments some years ago, which showed ( in practice) that with a 40 mm Luminar any closing of the aperture is suffering sharpmness, and much more with the 25 mm.

Regards

Volker
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Ralph Bottrill January 10, 2011 03:13AM
What is a micro 4/3 camera Volker?

Regards,
Ralph
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Volker Betz January 10, 2011 07:24AM
Hello Ralph,

a camera with the micro 4/3 standard like the Panasonic Lumix D2 and some others. One of their advantages is that there adapters available for many other lens connections.

Volker
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Matteo Chinellato January 10, 2011 07:45AM
hello Volker

the moviment in subjects of at 1 mm or under its normaly, we speack of pieces normaly seen with a SEM. Under my tripod I have put a weight for telescope of 2.5 kg. for eliminate the moviment. The 63 mm I use only for crystals at the 5 to 10 mm or up, for the others I use the 16 mm. Another its use a FF camera, type my Canon 5D mark II, or the 7D, another its use a compact camera, its totaly different, for not speack if you use fixed tubes the grain on the photo its many visible, I have personaly used fixed tubes in the first times, and is well visible the problems. At few time my move problems probably end with a new system I am under to buy

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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Stephan Wolfsried January 10, 2011 09:05AM
Matteo,

I can fully confirm what Volker wrote. Any stopping down of the Luminars costs sharpness. I use them fully open with good results.
My actual favorite is the Luminar 25 mm. The FOV ranges from 4,6 to 2,5 mm, which covers most of my specimens. With a stiff stand I get no artifacts like You showed in Your demo photo.
I fixed the bellows a second time beside the camera, which minimizes vibrations for sure. Se my thread on photgraphy. If I lengthen the bellows with distance rings the whole setup becomes easily affected from vibrations, and this with a 100 kg granite fozndation. So I found out the better way is to use the Luminar 16 mm without additional bellows extension (FOV min 1,5 mm).
instead of the Luminar 25 mm wth extended bellows and another 130 mm extension (several rings) with also FOV 1,5 mm.
With reduced light intensity I now work with 3 seconds exposure time and the shutter vibrations seem to be tolerable.

The resolution with the Luminar 16 mm is around one micron, even a bit less. Measured with a Wafer with test structures on it (0,30 ....1,5 microns). This is also a good method to evaluate the influence of vibrations and getting an optimum of the exposure time.
I did also experiments with 10...15 seconds, but this is a big challenge to my patience. And the improvement is not really a good trade off with time consumption.

Cheers Stephan
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Matteo Chinellato January 10, 2011 09:33AM
hello

yes but I work in orizontal not vertical with the bellow. Calculate the photo I have put in this post in the 2008 its pass 3 years, in 3 years many its change, now its this the result I have with crystals under the 1 mm

http://www.mindat.org/photo-345669.html
http://www.mindat.org/photo-274786.html
http://www.mindat.org/photo-355009.html
http://www.mindat.org/photo-355008.html
http://www.mindat.org/photo-348997.html

etc....

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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Matteo Chinellato January 10, 2011 09:40AM
A real problem I have now its find who polished the Zeiss lenses seen here in Italy I not find

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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OT. Ljøstad January 10, 2011 10:57PM
I have got the same "worms" of dots on some of my photos that I have taken with a Nikon D 700 DSLR and my Luminars. The worms originates from dust on the sensor. If I stack a photo from 15 different photos with a dust grain on the sensor, I got a worm consisting of 15 grey dots.

Your camera/mineral specimen (and mine) is not 100% aligned or moves sideways which is not a big problem since the stacking software aligns the photos and adds all the sharp areas of the different photos to form the finished, sharp photo. See one of my worms on the attached photo.

All dust grains on the sensor will always be sharp on all the photos, and because of the camera/specimen movements they form the unwanted worms. My worms dissapear when I clean the sensor. The worms on the finished photo are easy to remove with the retouching tools in Photoshop. It is also possible to retouch all the black dots from the different photos in batch mode if you have a lot of photos.

From time to time (but I never wait as long as 2 months) I clean the sensor of my camera with Sensor Swabs and Eclipse fluid. The only problem is the hight price of the Swabs and fluid.

One good way to see if you have any dust on your sensor is to remove the lens and take a photo without a lens towards a well-lt, white paper. It does not matter what shutterspeed you use. When you study the enlarged photo on your screen of your computor you will se the dots formed by dust partickles on sensor.



Edited 1 time(s). Last edit at 01/10/2011 11:18PM by OT. Ljostad.
open | download - worm.jpg (25 KB)
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Matteo Chinellato January 11, 2011 05:36AM
my sensors its polished, every some months I send all my camera to Canon for polishing the sensors. Its the lenses have dust into. The problem is find who polish this, seen its old lenses

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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Pavel Skacha February 01, 2011 01:14PM
Hello,

I bought Zeiss luminar 16 mm recently. I am in a "testing mode" right now, but I find something makes me unhappy. I noticed that when is a subject (crystal) in a deep cavity, so the objectiv is relatively close to the specimen, on the photos is good visible grey tarnish (place with lower contrast) roughly in the middle of the view. I will later try to place some photo of it, but have anyone some simillar experience?

Thanks, kind regards
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Volker Betz February 01, 2011 07:23PM
Hello Pavel,

you face the typical "problem" of short focal lenght: working distance is small. So ist difficult to photograph crystals in a "deep " cavity. I am photographing now almost 40 years ( with breaks) with luminar lenes.

From the photrographers ponit of view ther are a few rules:

1. Use excellent lenses
2. Only photograph objects which are suitable for photography ! dont wast time !
3. See 2 and don´t photghraph objects which are unsuitable
4. Newer show bad pictures to anyone, just descard it.

5. and most important:Only a few pecentage of pictures are good.

If you take 100 pictures only expect 1 is good.

6 . Be happy.

Regards

Volker
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Harald Schillhammer February 02, 2011 07:51AM
Pavel Skacha Wrote:
-------------------------------------------------------
, on the photos is
> good visible grey tarnish (place with lower
> contrast) roughly in the middle of the view.

This sounds very much like an internal flare problem. In addition, the very flat light angle that is necessary with such a short working distance might further enhance the problem by producing some kind of veiling flare, but that is usually not showing up as a central spot. I experienced something similar with a Leitz Photar 12,5mm. I have long ago stopped using it. Nowadays, when I do not use a microscope, I only use the 25mm Photar and a reverse-mounted EL-Nikkor 75mm, both on bellows.

It would be good to know how you have attached the Luminar. Some adapters/tubes are prone to produce internal flare.

Volker Betz Wrote:
-------------------------------------------------------

> 2. Only photograph objects which are suitable for
> photography ! dont wast time !
> 3. See 2 and don´t photghraph objects which are
> unsuitable
> 4. Newer show bad pictures to anyone, just descard
> it.


That depends on. Not every image has to necessarily be a candidate for winning a photography award. In many cases the documentary purpose outweighs the need for top notch quality. Not everybody has access to high quality equipment, although expensive equipment is no guarantee for high quality pictures ;).

Anyway, one should always try to set minimum quality standards for himself that even documentary photographs should meet, at least within the available technical possibilities.

Cheers

Harry
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Marko Burkhardt February 04, 2011 11:09PM
Hello Matteo!

I would like to know which objective do you use for this photo:


Was this a Luminar 16mm, a Photar 12,5mm or a Macro Nikkor 19mm?

Marko



Edited 2 time(s). Last edit at 02/04/2011 11:10PM by Marko Burkhardt.
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Matteo Chinellato February 05, 2011 05:39AM
if I remember is 16 mm

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
avatar
Pavel Skacha February 09, 2011 06:51AM
Dear Volker and Harald,

thanks for your messages.
Yes, maybe it is the problem in the adapter, bcs I have relatively long variant (about 5 cm, bought on ebay) and its inner side is not free of reflexions. I will try to fill the inner side by a velvet and test it again.

Thanks for your advices
Have a nice day
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Harald Schillhammer February 09, 2011 07:06AM
> (about 5 cm, bought on ebay)

Is that the cone shaped Beljan adaptor? If yes, then this is probably the culprit. Coating the inner side usually helps.

Cheers

Harry
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Pascal Chollet February 09, 2011 01:44PM
I have tested my luminar lenses at all apertures on my nikon D1x camera. here's what I found :

63mm : best results stopped down to 4
40 mm : best results stopped down to 2 & half
25mm : best results stopped down to 2
16mm : best results at full aperture.

What I do is using each lens at it's optimal aperture. I adjust the step between 2 photos according to the magnification and the resulting depth of field.
16mm luminar seems to be hard to use with digital cameras. I also have sharpening problems with this lens, and friends of mine, using this lens too, noticed the same thing.
I've got a (lucky) friend who owns both 16mm luminar & 19mm macro-nikkor. the results with the luminar can't stand no comparaison with the pics obtained with the macro-nikkor, really much sharper.

One suggested me that the problem could come from diffraction combined with digital CCD building, wich is not plane but made of photosites in the bottom of a honeycomb structure, after a lowpass filter. this structure really doesn't match fully stopped down lenses, producing more diffraction.

The notice of the Nikon D1x suggest not to stop down more than f/11 (with regular lenses) for best results. diffraction problems might happend really sooner with high magnification lenses.

Pascal
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Harald Schillhammer February 09, 2011 01:58PM
> The notice of the Nikon D1x suggest not to stop
> down more than f/11 (with regular lenses) for best
> results. diffraction problems might happend really
> sooner with high magnification lenses.
>
> Pascal

Do you use the Luminars on a bellows or other tube-like extension? You have to consider that each increase in tube/bellows extension results in a smaller effective aperture, meaning that even with fully open or weakly stopped down aperture you might get well beyond the diffraction limit when the extension exceeds a certain length.

Cheers

Harry
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Matteo Chinellato February 09, 2011 01:59PM
I use Nikkor 19 and Zeiss 16 but not full aperture, with full aperture the photo is not all in focus

Mindat Page

http://www.mindat.org/user-5018.html


Attrezzatura e tecnica sono solo l'inizio. È il fotografo che conta più di tutto. (John Hedgecoe)
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Pavel Skacha February 10, 2011 11:32AM
Yes Harry, you are right. I will do it today and hope it helps.

Thanks
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Dario Cericola February 10, 2011 05:43PM
Volker Betz Wrote:
-------------------------------------------------------



>
> Recent experiments showed me that any kind of
> shutter is not good for small fields of view. I am
> just making experiments with a Panasonic D2. It
> has no mirror and a different shutter: But even
> with that camera there is some loss of sharpness
> at short exposure time. But long exposure time
> helps. I could document that there is a
> significant difference between a 1/125 sec. and a
> 2 sec. exposure. 2 sec. a much sharper. I could
> measure a 1.5 micron resolution using a 15 mm
> Mikrotar of N/A 0.2.
>

Hallo Volker, just a curiosity... How do you measure the resolution?

Dario

----------------------------------------------------------------------------------------

Dario Cericola
My Mindat page http://www.mindat.org/user-7365.html#0
Periodic Table of Minerals http://www.mindat.org/blog.php/1612/Periodic+Table+of+Minerals
avatar
Volker Betz February 10, 2011 07:45PM
Recent experiments showed me that any kind of
> shutter is not good for small fields of view. I am
> just making experiments with a Panasonic D2. It
> has no mirror and a different shutter: But even
> with that camera there is some loss of sharpness
> at short exposure time. But long exposure time
> helps. I could document that there is a
> significant difference between a 1/125 sec. and a
> 2 sec. exposure. 2 sec. a much sharper. I could
> measure a 1.5 micron resolution using a 15 mm
> Mikrotar of N/A 0.2.
>

Hallo Volker, just a curiosity... How do you measure the resolution?

Hello Dario, measuring ? ist a more a rule of thumb estimation, by photographing a object micrometer with marks in 10 µm distance and about 2 µm wide. I am looking for a better micro object. 2 µm is about near the calculated resolution for a aperture 0,2.

I am still working on the subject. My object micrometer is for transmitted light, photographed in relefected light and has a cover. This causes some effects.

In some time I well have a better answer.

Volker
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Dario Cericola February 10, 2011 09:55PM
I see... I while ago I made some attempts in that direction, with a pretty similar approach. but it was quite a failure...

Dario

----------------------------------------------------------------------------------------

Dario Cericola
My Mindat page http://www.mindat.org/user-7365.html#0
Periodic Table of Minerals http://www.mindat.org/blog.php/1612/Periodic+Table+of+Minerals
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