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Zeiss Luminar's light problems

Posted by Matteo Chinellato  
avatar Zeiss Luminar's light problems
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?
dominik schlaefli
Re: Zeiss Luminar's light problems
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.
avatar Re: Zeiss Luminar's light problems
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


dominik schlaefli
Re: Zeiss Luminar's light problems
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
avatar Re: Zeiss Luminar's light problems
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
dominik schlaefli
Re: Zeiss Luminar's light problems
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.
avatar Re: Zeiss Luminar's light problems
January 05, 2008 12:38PM
    
its many few, calculate the anatase is a 0.8 mm crystal, in total is at 3 mm area
dominik schlaefli
Re: Zeiss Luminar's light problems
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
Re: Zeiss Luminar's light problems
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.
dominik schlaefli
Re: Zeiss Luminar's light problems
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).
avatar Re: Zeiss Luminar's light problems
January 07, 2008 07:12PM
    
hard this with a digital type the canon 20D and with several exposure for helicon
avatar Re: Zeiss Luminar's light problems
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.
avatar Re: Zeiss Luminar's light problems
January 07, 2008 09:06PM
    
this is a single shoot to a anatase of 0.8 mm. not polished, not change colors etc...


avatar Re: Zeiss Luminar's light problems
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
avatar Re: Zeiss Luminar's light problems
January 08, 2008 06:15AM
    
I have clear few months ago but in few days return the same.
Re: Zeiss Luminar's light problems
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")
avatar Re: Zeiss Luminar's light problems
January 08, 2008 08:27PM
    
Does your adaptator between bellows and your Canon 20D body have a lens inside?
avatar Re: Zeiss Luminar's light problems
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
avatar Re: Zeiss Luminar's light problems
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

[www.mindat.org]

last photos
dominik schlaefli
Re: Zeiss Luminar's light problems
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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