Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: bjanes on November 24, 2013, 09:31:52 am
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When taking close up shots with my Nikon D800e using the 4804 R1 Wireless Close-Up Speedlight System (two small flash units on either side of the lens) there are often innumerable white dots marring the image. I would like to know the mechanism for the formation of these artifacts and how one might get rid of them. The attached image was taken at f/11 and the raw file was processed in Lightroom using default sharpening and no NR.
I suspect they are specular reflections from small elements of the source. Aliasing could exacerbate the artifacts as could overzealous sharpening. Noise reduction. However, NR would degrade the image detail. The light from the flash is rather harsh and use of a more diffuse light source might reduce the artifacts. Does anyone know what is producing these artifacts and how one could mitigate the problem?
Thanks,
Bill
(http://bjanes.smugmug.com/Photography/Artifact/i-2K7Vcf2/0/O/20131123-_DSC2612.jpg)
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I suspect they are specular reflections from small elements of the source. Aliasing could exacerbate the artifacts as could overzealous sharpening. Noise reduction. However, NR would degrade the image detail. The light from the flash is rather harsh and use of a more diffuse light source might reduce the artifacts. Does anyone know what is producing these artifacts and how one could mitigate the problem?
Hi Bill,
Yes, I suspect they are specular reflections. You can try using some diffusing material to see if it helps enough.
If the subject surface is bumpy and waxy enough, you'll need very large diffusers to suppress the specularity. At certain angles, a polarizing filter on the lens may help for some angles but to more effectively suppress them, cross polarization must be used (polarizing foil outside(!) the diffuser and crossed polarizing filter on the lens).
I use a similar type of macro flash-unit (MT-24EX) on my Canon lenses, and I have fitted Stofen diffusers to the heads for softer light and more gradual fall-off with distance. Here (http://photography-on-the.net/forum/showthread.php?t=1324499) is a Canon oriented thread about all sorts of DIY solutions, I have to assume something similar is available or can be made for the Nikon macro flash-unit.
Cheers,
Bart
P.S. You can also try putting both (diffused) heads on one side of the subject, thus creating a (seemingly) larger illuminating surface, and a reflector on the other side to fill in the shadow side.
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I have always gotten that on orchids with sony cams. Orchids have a waxy cuticle.
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Hi Bill,
Yes, I suspect they are specular reflections. You can try using some diffusing material to see if it helps enough.
If the subject surface is bumpy and waxy enough, you'll need very large diffusers to suppress the specularity. At certain angles, a polarizing filter on the lens may help for some angles but to more effectively suppress them, cross polarization must be used (polarizing foil outside(!) the diffuser and crossed polarizing filter on the lens).
I use a similar type of macro flash-unit (MT-24EX) on my Canon lenses, and I have fitted Stofen diffusers to the heads for softer light and more gradual fall-off with distance. Here (http://photography-on-the.net/forum/showthread.php?t=1324499) is a Canon oriented thread about all sorts of DIY solutions, I have to assume something similar is available or can be made for the Nikon macro flash-unit.
Cheers,
Bart
P.S. You can also try putting both (diffused) heads on one side of the subject, thus creating a (seemingly) larger illuminating surface, and a reflector on the other side to fill in the shadow side.
Bart,
Thanks for the advice. My unit is similar in concept to the Canon unit, but Stofen does not make a diffuser for my unit. However, B&H lists a similar diffuser by Velo and I will order a set. The DIY suggestions are also interesting.
Another option is to use the extreme closeup adapters (SW-11 (http://www.bhphotovideo.com/bnh/controller/home?O=&sku=410441&is=REG&A=details&Q=)). As the name implies, these are for extreme closeups but they can also be positioned for use as a diffuser at greater distances.
Bill
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I tried in Photoshop CS6 a
Filter->Noise->Dust and Scratches
Radius 2
Threshold 57
on your image and it worked quite well without degrading it visibly (at least to my eyes).
Cheers
~Chris
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I have always gotten that on orchids with sony cams. Orchids have a waxy cuticle.
The waxy cuticle aggravates the situation, but the specular artifacts can be reduced with diffused lighting. I re-shot the orchid with diffuse daylight. The color and contrast are different, but the specular artifacts are largely eliminated.
Flash:
(http://bjanes.smugmug.com/Photography/Artifact/i-2K7Vcf2/0/O/20131123-_DSC2612.jpg)
Diffuse daylight:
(http://bjanes.smugmug.com/Photography/Artifact/i-LCcwgvx/0/O/112413_0004.jpg)
What do you think?
Bill
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What do you think?
Light is our key
to the Photography.
Using it direct
the artifacts erect.
Using it diffuse
you get kissed by the muse.
...
;)
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The waxy cuticle aggravates the situation, but the specular artifacts can be reduced with diffused lighting. I re-shot the orchid with diffuse daylight. The color and contrast are different, but the specular artifacts are largely eliminated.
Okay, that confirms the specular highlight assumption.
What do you think?
Some directional light helps to model the shapes a bit more, so a balance between both is preferred. I tend to try and create a main top backlight to show the translucent petals, and two 'front' flash heads at a ten to eleven o'clock and a three o'clock position with a 2:1 lighting ratio, to bring out shape and color. It can take a while to figure out a nice and natural looking lighting setup.
Cheers,
Bart
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The texture has visual value. It is a matter of keeping it under control. Using very diffuse light or a polarizer are fine. If however the resultant image has no sense of depth something is lost. You need some balance of the extremes.
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I would try convert the initial raw file with Iridient Developper using the hot pixel removal algos in detail tab.
Cheers,
Bernard