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Lichens and liverworts

 
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Lou Jost



Joined: 04 Sep 2015
Posts: 1800
Location: Ecuador

PostPosted: Mon Jan 30, 2017 5:17 pm    Post subject: Lichens and liverworts Reply with quote



This is a 100% crop of the above:


I used an Olympus 60mm macro lens and PEN-F with automatic in-camera focus bracketing (twenty to eighty shots per stack) to make these pictures. Magnification is around 0.25x to 0.75x. Some were hand-held (IBIS off) while others were taken with the camera on a tripod (IBIS on); there was no difference in sharpness between these. I used ISO 400 and a circular polarizer. Aperture was around f/4.5 which is the best aperture for my copy of this lens.

The handheld ones (like the one above) let me catch fleeting beams of light illuminating the lichens. Larger versions of these and others are available at
https://ecomingafoundation.wordpress.com/2017/01/30/a-coral-reef-of-lichens-bryophytes-and-algae-from-cloud-forest-twigs/



100% crop of above:


Others:





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

PostPosted: Tue Jan 31, 2017 1:29 am    Post subject: Reply with quote

Nice images!

Examples like this make a compelling case for the Olympus's style of rapid acquisition.

I have an observation/question about image sizes.

In your first pair of images, the one described as "100% crop of the above" is 994 x 822 pixels. When I match it up against the other image, Photoshop tells me that it's about 50% of the image width and 27% of the image height. That combination suggests a total image size of less than 6 megapixels, since 944*822/(0.5*0.27)=5747911. For the other pair it's worse, 950x820 and 47% x 58%, suggesting about 2.8 megapixels. Cross-checking against the link you give, I see that the first image comes across as 1975*2973=5871675 pixels, while the other one is 2000*1383=2766000.

So, it seems clear that "100% crop of the above" does not mean the same thing as "actual pixels from the camera", which is what I would normally expect it to mean.

Can you comment on the workflow? What do the details of these images look like at actual camera resolution?

--Rik
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Lou Jost



Joined: 04 Sep 2015
Posts: 1800
Location: Ecuador

PostPosted: Tue Jan 31, 2017 5:56 am    Post subject: Reply with quote

Thanks Rik.

My 100% crops do mean what they say. Those are the actual pixels from the stacked images. Stacked images were 20.4 Mp.

As you can tell from the different aspect ratios of the pictures I posted, all the stacked images were trimmed (sometimes severely) because the details were more interesting than the full frames. So sometimes a 100% crop is quite a large portion of the posted, trimmed image.

Here is the entire 20.4 Mp frame of the second image, reduced to fit the forum rules. (White balance of the trimmed image was adjusted slightly relative to the original image.) It is a tribute to the quality of the Oly image that even a severely trimmed detail can still look pretty good!


My workflow:

Tripod shots used a nodal slider to quickly and easily adjust magnification, and a wired remote release. White balance was obtained at the beginning of the day from a gray card; light quality changed slightly during the course of the shoot but I didn't bother to re-balance. Manual everything (white balance, aperture, shutter) so it doesn't change from frame to frame, IBIS off. Fully electronic completely silent shutter. Aperture usually around f/4.5. Polarizer adjusted to reduce glare. I overexpose about 1-2 stops on flatly lit images. I focus on the nearest detail of interest, press the shutter, and usually in less than a minute the Oly has taken the stack. If it looks like the stack wasn't deep enough, I press the shutter again; repeat as needed. A good number to start with is 40 frames at these low magnifications.

Handheld; all the same but IBIS on.

Stacked from RAW files converted to Tiffs in ACR, sharpening about 20-40% before stacking. I used DMap, retouched from the PMax image especially in the out-of-focus background, which showed unnatural banding and blotching in the DMap image. Final image adjusted using Photoshop's Camera Raw Filter. Then trimmed to focus on interesting details.
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rjlittlefield
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PostPosted: Tue Jan 31, 2017 12:46 pm    Post subject: Reply with quote

Thanks for the additional info -- most appreciated.

You wrote "out-of-focus background, which showed unnatural banding and blotching in the DMap image". That condition usually means that the contrast threshold selection was set too low. Standard recommendation is to make the OOF background go "black in preview". Have you tried that?

--Rik
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Ken Ramos



Joined: 27 Jul 2006
Posts: 6997
Location: lat=35.4005&lon=-81.9841

PostPosted: Tue Jan 31, 2017 6:11 pm    Post subject: Reply with quote

As they say, beauty is in the eye of the beholder. I could see a number of these framed and hanging in locations as to where they would be excellent conversation pieces. Surprisingly, I see no springtails!
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Wed Feb 01, 2017 2:30 pm    Post subject: Reply with quote

Rik, if I set the threshhold high enough to black out the background, there are many black areas in subjects as well. I thought that was to be avoided

Ken, thanks very much for your kind words. I really like this kind of subject and I had a lot of fun being able to make handheld stacks of them so easily.
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rjlittlefield
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PostPosted: Wed Feb 01, 2017 4:17 pm    Post subject: Reply with quote

Lou Jost wrote:
Rik, if I set the threshhold high enough to black out the background, there are many black areas in subjects as well. I thought that was to be avoided

That's not correct.

Here's what "How To Use DMap" tutorial says about it:
Quote:
A good strategy for setting the contrast threshold is to make most of the unfocused areas go black in preview, while leaving most of the focused detail in its normal colors.
...
When you're setting the slider, it's common to develop some black areas inside the focused subject, as shown here with many of the pink petals. Those black areas are generally harmless. They just represent parts of the subject where detail is either lacking or low contrast, and they won't cause a problem as long as they're surrounded by non-black areas where there is significant detail.

To explain in more detail...

Black-in-preview just represents areas where the depth will be interpolated from surrounding ares that are not black-in-preview. In typical cases, either that interpolation produces a good approximation to actual depth, or the area contains no detail worth caring about so it doesn't matter much what depth is used.

The only case where getting part of the subject black-in-preview causes a problem is when 1) that area does contain detail that you care about, and 2) the shape of the subject is such that interpolating depth from surroundings will give the wrong result. An example would be the bottom of a depression that is detailed but dimly lit, hence low contrast, and at a significantly different depth from its surroundings.

--Rik
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Wed Feb 01, 2017 4:59 pm    Post subject: Reply with quote

Rik, thanks for the explanation. Usually the black areas inside my subject are at the darker bottoms of depressions. They are probably noisier than surrounding bright areas.

I will experiment a bit. Even with the low threshhold, though, I had to spend time retouching within-subject areas that had light detail-free blotches where there should have been dark areas with some detail (which I could recover from the PMax image).
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rjlittlefield
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PostPosted: Wed Feb 01, 2017 5:09 pm    Post subject: Reply with quote

Lou Jost wrote:
light detail-free blotches where there should have been dark areas with some detail

The usual reason for this defect is that there is a nearby bright spot whose OOF blur extends across the dark area in some frames, and DMap sees the edge of the OOF blur as being higher contrast "detail" than the real detail in focused images. Raising the threshold will generally get rid of the light blotches, though it may still not recover detail in the dark regions if that detail is at a significantly different depth from its surroundings.

--Rik
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Wed Feb 01, 2017 5:13 pm    Post subject: Reply with quote

Thanks, tat's encouraging, Rik. I'll play with higher threshholds. It would be nice to be able to avoid that retouching step.
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