"Sparkles" in Zerene Pmax

Deanimator · Post by **Deanimator** » Fri Sep 29, 2017 1:42 pm

Lately, I've noticed glittering washed out areas in my Pmax stacks.

These don't appear in the unstacked images.

I told it not to preserve dynamic range and it got a little better, but it's still unacceptable. I changed the threshold for Dmap from 20 to 40 and the issue is much less that way. However I prefer Pmax because I get fewer artifacts.

Am I missing a setting somewhere?

rjlittlefield · Post by **rjlittlefield** » Fri Sep 29, 2017 2:41 pm

There is no setting for PMax that will make the sparkles go away.

Typically sparkles occur when you have relatively "hard" illumination that produces very bright specular highlights. Those highlights actually spread out and move around a little from one frame to the next. In each different position they look like focused detail. PMax is relentless about preserving focused detail, so it ends up producing a result that is an amalgam of all those different highlights from multiple frames.

The most powerful attack on sparkles is to use more diffused "soft" illumination. See Reflections of hard and soft light in a spider's eye for illustration and discussion.

As you've noticed, DMap has much less tendency to produce sparkles. That's because DMap is not as relentless about preserving focused detail, and unfortunately that goes hand-in-hand with producing more artifacts when you have complicated geometry with lots of foreground/background overlaps.

Often the best final result is produced by using the retouching tool to merge the best bits of DMap and PMax outputs. That way you get to choose which is the better rendition for each part of your subject.

By the way, the percentage number shown for the DMap threshold slider is just the fraction of frame area that is covered by the corresponding mask. The best setting can vary from 0 to almost 100%, depending largely on composition. If there's a clear distinction between focused subject and unfocused surroundings, the best setting is usually whatever makes the mask cover all the unfocused areas. But there are special cases where other settings can produce more useful results, especially if you're retouching. For more information, see the tutorials How To Use DMap and
Advanced Retouching .

--Rik

Deanimator · Post by **Deanimator** » Fri Sep 29, 2017 11:14 pm

rjlittlefield wrote:There is no setting for PMax that will make the sparkles go away.

Typically sparkles occur when you have relatively "hard" illumination that produces very bright specular highlights. Those highlights actually spread out and move around a little from one frame to the next. In each different position they look like focused detail. PMax is relentless about preserving focused detail, so it ends up producing a result that is an amalgam of all those different highlights from multiple frames.

The most powerful attack on sparkles is to use more diffused "soft" illumination. See Reflections of hard and soft light in a spider's eye for illustration and discussion.

As you've noticed, DMap has much less tendency to produce sparkles. That's because DMap is not as relentless about preserving focused detail, and unfortunately that goes hand-in-hand with producing more artifacts when you have complicated geometry with lots of foreground/background overlaps.

Often the best final result is produced by using the retouching tool to merge the best bits of DMap and PMax outputs. That way you get to choose which is the better rendition for each part of your subject.

By the way, the percentage number shown for the DMap threshold slider is just the fraction of frame area that is covered by the corresponding mask. The best setting can vary from 0 to almost 100%, depending largely on composition. If there's a clear distinction between focused subject and unfocused surroundings, the best setting is usually whatever makes the mask cover all the unfocused areas. But there are special cases where other settings can produce more useful results, especially if you're retouching. For more information, see the tutorials How To Use DMap and
Advanced Retouching .

--Rik

Thanks.

Here's the final result I got with Dmap before I had to go to work:

[/img]

ChrisR · Post by **ChrisR** » Sat Sep 30, 2017 5:00 am

This is Pmax retouched with DMap??

Diffuse diffuse diffuse.
(+ make sure lens is clean, & without any filter.)

Look very carefully to see if a point's blur-sparkle goes from (say) North-South to East-West when you focus through it. That longitudinal variation in astigmatism is annoyingly common. Try to diffuse until there isn't any of that sort of blur, or it all looks like detail, to the stacker, and you end up with a sort of cross. Hard to tell at this scale.

Deanimator · Post by **Deanimator** » Sat Sep 30, 2017 8:48 am

ChrisR wrote:This is Pmax retouched with DMap??

No, it's straight Dmap with a few tweaks in settings.

This image was taken before I started this thread.

Since I'm still working on my new interim macro rig, I was using the Jansjos instead of flash.

I had the Jansjos relatively close to the subject (a 3/8" to 1/4" ballhead adapter). They have pingpong ball diffusers on them. One was positioned to light from above and the other from front left.

About how far away should they be for something that size?

Lou Jost · Post by **Lou Jost** » Sat Sep 30, 2017 8:58 am

Diffusers on the lamps don't do much good; they will take up only a small proportion of the "sky" as seen by the subject. You need diffusers close to the subject, so the whole "sky" looks evenly lit from the subject's point of view. .

Deanimator · Post by **Deanimator** » Sat Sep 30, 2017 10:31 am

Lou Jost wrote:Diffusers on the lamps don't do much good; they will take up only a small proportion of the "sky" as seen by the subject. You need diffusers close to the subject, so the whole "sky" looks evenly lit from the subject's point of view. .

I'll have to make something, time permitting.

My regular light tent for still lifes is too big.

Deanimator · Post by **Deanimator** » Sat Sep 30, 2017 11:41 am

An interesting visual demonstration of what others have posted here. I think I have in fact seen the positional shift illusion recently while shooting similar reflective subjects, with insufficient diffusion.

http://www.stackrail.info/index.php/en/ ... ht-or-else

mawyatt · Post by **mawyatt** » Sat Sep 30, 2017 12:15 pm

Deanimator wrote:
Lou Jost wrote:Diffusers on the lamps don't do much good; they will take up only a small proportion of the "sky" as seen by the subject. You need diffusers close to the subject, so the whole "sky" looks evenly lit from the subject's point of view. .
I'll have to make something, time permitting.

My regular light tent for still lifes is too big.

eBay has some small inexpensive tents, I have that's only a 1' cube. It can easily fit inside another larger one. I've used this double diffused tent often, and also found that a small foam cup over the lens end inside a small tent works well of some subjects.

With metallic or shinny subjects as Chris said "Diffuse, diffuse...diffuse".

Deanimator · Post by **Deanimator** » Sat Sep 30, 2017 12:29 pm

mawyatt wrote:eBay has some small inexpensive tents, I have that's only a 1' cube. It can easily fit inside another larger one. I've used this double diffused tent often, and also found that a small foam cup over the lens end inside a small tent works well of some subjects.

I've gotten very good at making these things, so I'll probably build something from PVC and packing foam tomorrow.

mawyatt wrote:With metallic or shinny subjects as Chris said "Diffuse, diffuse...diffuse".

That does appear to be the case. I didn't notice it until I started shooting small chrome plated items.

mawyatt · Post by **mawyatt** » Sat Sep 30, 2017 2:15 pm

Deanimator wrote:
mawyatt wrote:eBay has some small inexpensive tents, I have that's only a 1' cube. It can easily fit inside another larger one. I've used this double diffused tent often, and also found that a small foam cup over the lens end inside a small tent works well of some subjects.
I've gotten very good at making these things, so I'll probably build something from PVC and packing foam tomorrow.

mawyatt wrote:With metallic or shinny subjects as Chris said "Diffuse, diffuse...diffuse".
That does appear to be the case. I didn't notice it until I started shooting small chrome plated items.

Think I paid about $10 for the small 1' cube tent.

Deanimator · Post by **Deanimator** » Sun Oct 01, 2017 1:16 am

mawyatt wrote:Think I paid about $10 for the small 1' cube tent.

I've got everything I need (for several very different configurations) just lying around my apartment.

I should have something by dinner time tomorrow. I'd have something by lunch time, but I just got home from work and dinner and it's 4:15am.

Deanimator · Post by **Deanimator** » Sun Oct 01, 2017 10:50 am

The same thread adapter pictured above.

I spent about five minutes making a diffuser out of card stock, held onto my subject stage with a couple of clothes pins.

The light from above is still a bit harsh. I need to move that lamp a little farther away.

Unaltered Pmax and Dmap:

ChrisR · Post by **ChrisR** » Sun Oct 01, 2017 4:19 pm

Simple paper draped near the subject, is usually fine. Ideas here: http://www.photomacrography.net/forum/v ... hp?t=25935

Deanimator · Post by **Deanimator** » Sun Oct 01, 2017 5:11 pm

ChrisR wrote:Simple paper draped near the subject, is usually fine. Ideas here: http://www.photomacrography.net/forum/v ... hp?t=25935

So far the card stock seems to work relatively well. It has the advantage of being stiff enough to have its own structural strength.

I'm doing a 103 image stack of a silver cufflink right now. I pulled the lamps back a bit. We'll see how that comes out.

Update: That one didn't come out well due to weird reflections (the camera) in the subject.

I just made a much smaller diffuser which sits right over the subject.