Diffusion Solved?

Images taken in a controlled environment or with a posed subject. All subject types.

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MarkSturtevant
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Post by MarkSturtevant »

Its really nice. Of course there is the blown out highlight, but you might be rid of it by changing the angle of the diffuser for this particular subject. For a different subject, another angle could do the trick.
One could see if its working with one picture, in case you are doing stacking.
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rjlittlefield
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Post by rjlittlefield »

The blown out highlight puzzles me.

By itself, a blown out highlight just says that there's a lot more light coming from one particular range of angles than there is from all the others. That just says that Deanimator's eight layers of diffusion are not enough, which could be easily explained as each layer is awfully weak, or there's not enough separation between layers, or not enough separation between the diffusion and the actual light source, or that there's some light creeping around the edge of the diffuser.

The puzzling thing is that I don't understand why that particular area of the cuff link is blown out, while other areas of the link around the bottom of the frame look like they should be the same angles but those all range from mid-gray to very dark. I must be misunderstanding the shape of the cuff link somehow, but I'm sure not getting it.

--Rik

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Post by ChrisR »

It looks like the main light is to the right of the camera, and that edge happens to have the right angle.
I suspect, from the packing materials I've tried, that they aren't as good as diffusing as their appearance might suggest, and a lot of light goes straight through. If there's no gap between them it'll go straight through the lot, being attenuated more than diffused.
8 layers of many materials would be enough.
One polystyrene cup might well do better.
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Post by Deanimator »

rjlittlefield wrote:I must be misunderstanding the shape of the cuff link somehow, but I'm sure not getting it.
It's an odd shape, which makes it an interesting challenge.

Take a couple of paperback novels.
Place them side by side.
Then rotate them slightly around an imaginary horizontal axis passing through them at the halfway mark.

That's what their actual shape is.

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Post by Deanimator »

ChrisR wrote:One polystyrene cup might well do better.
How would you employ the cup?

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Post by ChrisR »

If you put the cup right over the subject with the lens through a hole in the flat base, and only shine light onto the cup side(s), (preferably more than one), you get pretty diffuse light. Whatever makes it through the cup, bounces around off the white insides.
One light, with a mirror on the other side, works quite well.
If you let some of the light get into the edge of the cup, (NOT reaching the subject) that'll bounce around a fair bit, but you get more directionality.

That's the idea here http://www.photomacrography.net/forum/v ... hp?t=25935. Follow the link to NikonUser's post in there which has a picture.

The UK's Natural History Museum, for routine beetle shots, uses a polystyrene cup with a twin flash, through the cup from about 3"/8cm each side. If you put them too close you get a hot spot.

If you need more-even light you need it to come from every direction equally. Normally an extra tube of ordinary paper around the subject is enough. If you want to photograph Mike's shiny silver balls of solder then it gets silly:
http://photomacrography.net/forum/viewt ... 692#185692
Note the two diffusing cubes (very useful and quite cheap).

Some black buttons, make quite a good indicator of/for how a difficult subject will turn out:
http://photomacrography.net/forum/viewt ... 256#197256
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mawyatt
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Post by mawyatt »

Think this is what Chris is talking about, a white styrofoam cup (various sizes) on my Vertical Setup. Cup just sits on base covering subject (wafer in this case) with hole in top for lens to poke thru. To keep light from entering cup from top is the black square cardboard around lens. Strobes are around perimeter and illuminate cup sides.

As Chris mentioned this works extremely well, I also diffuse strobes with packing foam to further diffuse light.

I've also had success with a smaller white styrofoam cup over lens end protruding over and completely around subject. I often use this on my horizontal setup inside a small light tent at higher magnifications so lens doesn't move much, thus illumination is almost uniform from stack start to stop.

Best,Image
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Post by rjlittlefield »

Deanimator wrote:
rjlittlefield wrote:I must be misunderstanding the shape of the cuff link somehow, but I'm sure not getting it.
It's an odd shape, which makes it an interesting challenge.

Take a couple of paperback novels.
Place them side by side.
Then rotate them slightly around an imaginary horizontal axis passing through them at the halfway mark.

That's what their actual shape is.
Yeah, I figured out that much.

But here's my problem:

Image

The two surfaces indicated by the yellow markup look to me like they should be basically the same shape and orientation.

But the upper one has a blown out highlight, while the other one has an almost dark face.

I hope I'm not the only one who finds this puzzling.

So then my question is: where does the light come from, that makes the blown out highlight?

And the answer is, at the moment, I don't have a clue. Maybe it's a secondary reflection, but I can't figure out from where.

The reason I explain this is mainly to make the point that no matter how hard we other forum members try to help you, ultimately you have to figure it out for yourself, because you're the fellow with the subject in hand, with control of where the lights and diffusers are.

By far the best recommendation I can make at this point is to pick up a copy of Light: Science and Magic: An Introduction to Photographic Lighting 3rd Edition. That edition is almost free at this point -- Amazon is quoting a price around $6.50 for a used copy, including shipping. The book does not put as much emphasis on diffusion as we normally need for macro/micro work, but the discussions of "family of angles" will be hugely helpful to you in figuring out why you're getting certain results, and how to get others.

--Rik

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Post by Deanimator »

rjlittlefield wrote:Yeah, I figured out that much.

But here's my problem:

Image

The two surfaces indicated by the yellow markup look to me like they should be basically the same shape and orientation.

But the upper one has a blown out highlight, while the other one has an almost dark face.

I hope I'm not the only one who finds this puzzling.

So then my question is: where does the light come from, that makes the blown out highlight?

And the answer is, at the moment, I don't have a clue. Maybe it's a secondary reflection, but I can't figure out from where.
It ought to be puzzling, since they're not just an odd shape, they're an odd texture. You actually have to see them in person to really understand.

The top half is polished smooth, while the bottom half has a brushed finish.

This creates a very interesting, but also very challenging lighting effect. The exposure, etc., for one is always going to negate that for the other. You'd almost have to do a sort of HDR thing and combine them. Note the artifact around the bottom left hand corner of the top half.

As far as the placement of the Jansjo's, both of them (in the above image) are at approximately subject level and maybe 3" to 4" from the diffusion material, which was too close.

I did another capture last night, with them at least 6" to 8" inches away (see below). Still not perfect, but at least I got the composition better. (but not perfect. You can still see just a hint of the green plastic grip of the carpenter's clip holding the subject.) I may have bumped up the exposure a little too much, as well.

I actually looked around for a styrofoam cup, but I threw a stack of them away when I "cleaned" the living room... before creating almost as big a mess with the tools I use to fabricate my gear. I'm going to pick up a sleeve of them today when I go to the store. I've still got tracing paper I haven't used yet too.

Image

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Post by MarkSturtevant »

There are several factors that cause a blown out highlight. A key one here must be that there is a bit of the shiny object that is facing directly at the camera sensor, so a high % of the reflected light rays are heading right at the sensor. If the object (or the camera) could be turned just a teeny bit it would not come out as bright. Rather than fuss with the myriad parameters of the diffuser and so on, one could just change an angle slightly.
Not sure why the other similar area is not doing it, but maybe its sitting in a more shadow or is less directly illuminated by the flash because of its position.

When I am out and about taking pictures of bugs, I invariably have to work pretty hard to reduce this problem with each shiny bug that I find. But the next shiny bug will probably require slightly different conditions. It would be less interesting if it were easier, I am sure. :)
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Jan Steinman
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Post by Jan Steinman »

mawyatt wrote:Think this is what Chris is talking about, a white styrofoam cup (various sizes) on my Vertical Setup. Cup just sits on base covering subject (wafer in this case) with hole in top for lens to poke thru. To keep light from entering cup from top is the black square cardboard around lens. Strobes are around perimeter and illuminate cup sides.
I don't mean to hijack this thread, but have you considered other lighting options? Yours looks very complicated, but with the advantage that you've done a great job of making do with what you have.

Have you considered a ring light? I love these things, and have several!

Here's an example, using an Olympus T-8 ring flash:
Image

Here is what the Olympus T-8 ring flash looks like:
Image
:::: Jan Steinman ::::

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Post by Deanimator »

The cuff link with the styrofoam cup treatment:

Image

rjlittlefield
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Post by rjlittlefield »

Deanimator wrote:Note the artifact around the bottom left hand corner of the top half.
The bluish ring does not look like any artifact that I am familiar with. Can you show us what that looks like in the source images?
The top half is polished smooth, while the bottom half has a brushed finish.
Yes, polished smooth versus brushed explains a lot.

So then exploiting that knowledge...

If the top half is polished smooth, then it acts like a mirror. What curved mirrors do is to show a reflection of the environment that is distorted geometrically but faithful for brightness. When you have a blown out reflection in a mirror, that inevitably means that your illumination is a lot brighter from some angles than from others. In other words, it is not diffused enough to tame the specular reflections.

There is a balancing act here. If you put a mirror ball inside an integrating sphere that is uniformly bright except where the lens sticks through, then what you'll see is a uniformly illuminated circle with a dark spot in the middle of it. That's because at every angle the reflection shows either the integrating sphere or the black hole of the lens. But uniformly bright means that all the modeling goes away -- the mirror ball no longer looks like a ball.

So, to get a good rendering of the mirror ball, what you need is illumination that varies enough with angle to provide modeling, while not concentrating so much light in any one area that you get unpleasantly bright highlights from reflecting that.

Similarly, in this last image, the cuff link with the styrofoam cup treatment, that dark face on the lower edge of the glossy half means that it is reflecting a piece of the environment from which very little light is coming. If you like the darkness, then the setup is working well; if you don't like the darkness then you need to figure out what part of the environment is being reflected, and how to make that part of the environment light up.

--Rik

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Post by rjlittlefield »

Deanimator, for what it's worth, I have just now reopened my copy of the Light Science and Magic book, to refresh my memory of its contents.

There is an entire chapter titled "Metal". In the introduction to the chapter, the authors write that
There are about a half dozen classic subjects that all photographers are supposed to encounter as they learn lighting. These subjects teach basic techniques that enable us to light anything. Metal is one of the classic subjects for good reason. Brightly polished metal produces almost nothing but unpolarized direct reflection. This constancy makes metal a real joy to photograph. It is predictable. It plays by the rules. We can tell before we begin to light the scene what size the light needs to be."
I love that bit about "a real joy to photograph". One man's joy is another man's PITA, I think. Anyway, that quote is on page 111 of the book that I referenced.

The chapter then continues with a discussion of principles, before getting into their first example, a shiny kitchen spatula, which is finally nicely rendered on pages 124 and 128. The intervening 13-17 pages are filled with diagrams and results from a variety of setups that are very illustrative of concepts, though not so good individually for illustrating the spatula.

Again, I strongly recommend picking up a copy of that book.

--Rik

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Post by mawyatt »

Jan Steinman wrote:
mawyatt wrote:Think this is what Chris is talking about, a white styrofoam cup (various sizes) on my Vertical Setup. Cup just sits on base covering subject (wafer in this case) with hole in top for lens to poke thru. To keep light from entering cup from top is the black square cardboard around lens. Strobes are around perimeter and illuminate cup sides.
I don't mean to hijack this thread, but have you considered other lighting options? Yours looks very complicated, but with the advantage that you've done a great job of making do with what you have.

Have you considered a ring light? I love these things, and have several!

Here's an example, using an Olympus T-8 ring flash:
Image

Here is what the Olympus T-8 ring flash looks like:
Image
Hi Jan,

Yes I tried ring lights many many years ago (one of my first lighting attempts, I have a Sigma Ring light & the Nikon Macro lighting system), without much success. The semiconductor chips I often image are quite a bit different than coins or other macro subjects, and require a very unique lighting.

As Rik points out above about the spherical mirror and uniform illumination, I have chips with thousands of tiny (100 & 40 microns) spherical mirrors called solder balls, and are a "joy" :roll: to image without serious specular artifacts!

Chris points out my massive attempt at dealing with this here.
If you want to photograph Mike's shiny silver balls of solder then it gets silly:
http://photomacrography.net/forum/viewt ... 692#185692
Note the two diffusing cubes (very useful and quite cheap).
I've subsequently reduced this massive array to 5 strobes and a few reflectors in a smaller space (requirement from the boss :roll: ).

Nice work on your ring mod!!

Best
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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