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could this stack be improved by so called slabbing

 
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Lothar-Gutjahr



Joined: 27 Dec 2011
Posts: 237
Location: Greece Perachora/Loutaki

PostPosted: Sat May 04, 2013 4:45 pm    Post subject: could this stack be improved by so called slabbing Reply with quote

Yesterdays little wasp got cought in a pizeria, so i got a new model. This picture results from stacking 180 fotos 20 µm apart, using Luminar 40 mm and is stacked with Pmax in one row.

In which case one would use that slabbing ? I am a little stupid to understand when one makes use of it.



The picture underwent enhance contrast and unsharp mask but is not cleaned. One little stripe of the bottom part is cut off, i had messed up.
No further actions after downsizing.

Another aspect i observed is sort of cromatic problem in the yellow areas. Is that a sensor problem on my Canon or by the lens used ?

Thanks for a little help and good night (1:45 am here )

Lothar
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Sat May 04, 2013 5:50 pm    Post subject: Reply with quote

The big benefits of slabbing are in two situations:

1. Retouching is always simpler and faster when you can retouch from say 10 slabs instead of 100 original frames.

2. Sometimes you can get use PMax on pass #1 to flatten each slab, then use DMap on pass #2 to assemble the intermediate slab outputs into a single final output. In this case there are two benefits: a) PMax has less chance to accumulate noise than if it did all the frames at once, and b) it's much faster to try various settings for DMap parameters.

As far as I know, there is no advantage to slabbing if you're going to process the whole stack with PMax and then stop.

About the chromatic problem...

I don't know exactly what problem you're looking at.

It is common for bright yellows to saturate the red & green sensors. That makes the yellow areas go almost featureless.

This can be addressed by underexposing when shooting, then carefully applying color adjustments in post-processing. It is best to do this by shooting in raw and processing as 16-bit TIFF, but of course the workflow is longer and takes more disk space that way.

--Rik
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Chris S.
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Joined: 05 Apr 2009
Posts: 3334
Location: Ohio, USA

PostPosted: Sat May 04, 2013 7:10 pm    Post subject: Reply with quote

Since these threads are read by folks other than the OP, and long after the time of writing, let me point out that slabbing is currently a "young" process. The best practices and benefits of slabbing are probably not yet fully understood. As someone who makes slabs nearly every day, I largely agree with Rik's summary as covering present (May 2013) slabbing knowledge. But I'm seeing additional nuances in slabbing as I work with it, and suspect that in the not-distant future, additional benefits of slabbing will emerge.

If I were shooting Lothar's pizzeria wasp, I would not expect slabbed results to be automatically better than non-slabbed results in a straight DMap workflow. Rather--and as Rik said--I would expect that retouching would be easier, that it would be quicker to try various combinations of PMax and DMap, and in DMap, it would be quicker to experiment with contrast thresholds and estimation radii. So while a slabbed result would not be immediately better, it might well offer a faster path to betterness with easier and more robust tweaking.

However, since the wasp looks pretty good with standard techniques, I might not bother with much tweaking. But I would slab it anyway! This is because slabbing is very easy to do and increases options for improvement at practically no cost in time or trouble.

While as yet poorly understood, I suspect there are other situations in which the benefits of slabbing may be greater. These situations will most likely involve subjects that give poor results when stacked normally. Recently, I've been working with a subject that has several times turned out better with slabbing, even when no tweaking or retouching was done. It's too soon to generalize, but my sense is that we're going to learn additional uses for slabbing as the technique becomes more widely understood.

One additional slabbing approach does seem immediately useful for certain difficult subjects: Making slabs with DMap, instead of PMax, and stacking these slabs with DMap, but with different contrast thresholds, estimation radii, and even alignment parameters than those used to make the slabs. In some cases I've tried, this has worked very well. I'll soon be making a version 2 of SlabberJockey that permits a choice between making DMap and PMax slabs.

But none of this is likely to apply to subjects such as this wasp, which seems to work just fine with standard stacking.

--Chris
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Lothar-Gutjahr



Joined: 27 Dec 2011
Posts: 237
Location: Greece Perachora/Loutaki

PostPosted: Mon May 06, 2013 2:57 pm    Post subject: Reply with quote

Hi Chris and Rik,

i have done some experimenting. First foto shows a straight trough stack and the second was divided in 5 slabs.

one row stacked


slabbed


Also i did a little unsharp on the forumsize.

My feeling and observation in missing details says the direct stack is better ?
Example the hairs on the left eye.

Lothar

addendum:

in the upper fotos one can see in the left eye, the beginning of detoriation. Todays foto shows the progress. Perhaps gas below that coverskin of the eyes:

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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Mon May 06, 2013 4:56 pm    Post subject: Reply with quote

Lothar-Gutjahr wrote:
My feeling and observation in missing details says the direct stack is better ?
Example the hairs on the left eye.

This looks like it was processed with PMax within each slab, and DMap across slabs. The lost hairs around the eye are typical of DMap. The loss-of-detail halos around other hairs that were preserved are also typical of DMap.

For hairy or bristly subjects, it would work better to run PMax across slabs also. The result will be almost identical to what you would get from a single PMax run of the entire stack, but retouching from the intermediate slabs would be simpler.

--Rik
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Lothar-Gutjahr



Joined: 27 Dec 2011
Posts: 237
Location: Greece Perachora/Loutaki

PostPosted: Mon May 06, 2013 10:09 pm    Post subject: Reply with quote

Hi Rik,

your right. Here is the Pmax-conclusion of the slabs:



The missing hair is back, grin. The fotos are completly unretouched.
Whereas considering my mikrofotos are done on my "UFOMI" and are vibrated by a stepper i have to fixmount each object not to start moving.
This was important for the x-y-table also and since the beginning of doing so, my stacks are relativly clean. Having marks from dirth on the camera sensor i usuable clean with PSE 8.
Before buying the Canon 1000 D, to have the shots done on ufomi in lifeview, i used a Sony NEX-5 ( without N) from which i talk about "earthquake shutter". So even not vibrating with a stepper, the objects moved a little while stacking.

Idea I like to point out for all beginners in stacking, that there is a physical behavior , objects move under certain vibrations. For this reason also, my ufomi has its own little table mounted to the wall and not staying on the floor, where even cars driving on the nerby street will influence this behavior.
This may sound to be a little overdoing it. But as soon one starts doing stacks on magnifications going to 500 x fold or more, this are unavoidable circumstance of stackers life. Idea

In the years after WWII a clockmaker in my hometown produced clocks synchronized to the line frequency using a velvety material on top of a little electric magnet which kept a rotating plate spinning. This just to help your powers of imagination.

Greetings Lothar
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Lothar-Gutjahr



Joined: 27 Dec 2011
Posts: 237
Location: Greece Perachora/Loutaki

PostPosted: Tue May 07, 2013 3:45 am    Post subject: Reply with quote

This morning a stack, to observe the progress of delamimation on the eyes of the small wasp, was made.
The red arrow points to one of the markings left over from dirthy sensor and shows the minimazed movement across 100 shots done.


It reminded me on the little wasp in that amber i stacked few month ago:



It´s interesting to watch a proces of about 4 days decomposition on a subject about 40 million years old.
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