Refllector bowl for test shots

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gardenersassistant
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Refllector bowl for test shots

Post by gardenersassistant »

AdminCR note: This thread continues from the Reflector Bowl Test Shots images thread which is HERE
MarkSturtevant wrote:
Fri Jun 25, 2021 8:35 am
Very nice!
Thank you. :)
MarkSturtevant wrote:
Fri Jun 25, 2021 8:35 am
By coincidence I've been tinkering with a diffuser that relies more on reflection than diffusion as well. The basic idea is to mount a reflector thingy directly in front of the flash head, and to have the entire interior of the diffuser space also be reflective. In this way there is no direct light path from the flash element to the subject. The reflective material that I rely on is HVAC tape.
I will be happy to share what iv'e got should a thread appear for that.
Interesting approach. I can imagine it being a bit tricky to construct. I've thought about something similar but never worked out how to build it. How are you finding it in use?

I'm using bounce flash to get diffuse reflected light, with no transmissive diffusion. I'm bouncing the flash light off of printer paper which is lining a 10 inch diameter hemispherical bowl. The paper is overlaid on somewhat crumpled aluminium foil.
Nick

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Re: Reflector bowl test shots

Post by MarkSturtevant »

My reflector right now is a triangular wedge shaped cardboard form, covered in HVAC tape. This is suspended just in front of the flash with struts, rather like how a secondary mirror is suspended inside a reflector telescope by "spider vanes".
I am getting the best results I've ever had, but I've certainly seen better results elsewhere. I was drawn to using silvery reflective surfaces as opposed to white reflective surfaces. I wonder about the pros and cons of that.

Have people seen this Facebook group: https://www.facebook.com/groups/1833312 ... j_approved. I expect many have.
Mark Sturtevant
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Re: Reflector bowl test shots

Post by gardenersassistant »

MarkSturtevant wrote:
Fri Jun 25, 2021 4:12 pm
My reflector right now is a triangular wedge shaped cardboard form, covered in HVAC tape. This is suspended just in front of the flash by struts. This is done a bit like how a secondary mirror is suspended inside a reflector telescope by spider vanes.
I am getting the best results I've ever had, but I've certainly seen better results elsewhere. I was drawn to using silvery reflective surfaces as opposed to white reflective surfaces. I wonder about the pros and cons. I could post pictures here...
Please do. I would welcome that.
MarkSturtevant wrote:
Fri Jun 25, 2021 4:12 pm
Have people seen this Facebook group: https://www.facebook.com/groups/1833312 ... j_approved. I expect many have.
That looks interesting. I have a Facebook account but I don't use it for anything. I tried joining the group but ran into a really weird question they were asking. I have no idea if I'll be let in or not.
Nick

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Re: Reflector bowl test shots

Post by MarkSturtevant »

Facebook groups often ask questions, including odd questions, just to see if you are serious / not a troll / not a robot (maybe).
I am preparing some pictures of what I've got going on right now.
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Re: Reflector bowl test shots

Post by gardenersassistant »

MarkSturtevant wrote:
Fri Jun 25, 2021 5:09 pm
Facebook groups often ask questions, including odd questions, just to see if you are serious / not a troll / not a robot (maybe).
Ah, OK. That might explain it.
MarkSturtevant wrote:
Fri Jun 25, 2021 5:09 pm
I am preparing some pictures of what I've got going on right now.
I'll look forward to seeing them.
Nick

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Rework and reposts of my images posted in this forum are always welcome, especially if they come with an explanation of what you did and how you did it.

gardenersassistant
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Re: Reflector bowl test shots

Post by gardenersassistant »

MarkSturtevant wrote:
Fri Jun 25, 2021 5:09 pm
I am preparing some pictures of what I've got going on right now.
Since we are into sharing info on this, here is the setup I'm testing at the moment.

Image
1923 Illustration 2 by gardenersassistant, on Flickr

Image
1923 Illustration 1 by gardenersassistant, on Flickr

Image
1923 Illustration 3 by gardenersassistant, on Flickr

It is a different approach from my previous one.

Image
1912 1 by gardenersassistant, on Flickr
Nick

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Re: Refllector bowl for test shots

Post by MarkSturtevant »

Screen shots of that rig are definitely going into my "Diffuser Porn" folder! :) On he older design: Is that cloth the special silk that I've heard about from time to time?
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Re: Refllector bowl for test shots

Post by MarkSturtevant »

Ok, here goes! This is my diffuser design. Like the one from gardenerassistant, this design emphasizes reflected light more than diffused light. Its a thing i've been evolving for two years now. Already laying awake in bed, worrying if my diffuser is adequate, but that is the way it goes!

I was long ago drawn to the versatility of these wonky-looking twin flashes. One can control the direction of lighting, and since the diffusers are easily designed to not be attached to the macro lens one can easily switch out lenses in the field.
ImageTwin flash diffusers. Front view. by Mark Sturtevant, on Flickr
ImageA twin flash allows more directional control of light. by Mark Sturtevant, on Flickr

A. The diffuser bowls are cheap items bought from a party store, and are 7 inches across at the front. The face of the diffuser is a thin layer of wrapping foam (~ 1 mm thick), plus there are some extra layers in front as a last-ditch effort to discourage hot spots.
B. The back of the diffuser. I know it looks very messy. Dremel cutting tools were used to cut a T-shaped hole in the back of the bowls. This was to fit the T-shaped flash head. Accessory holes were also drilled alongside to receive zip-ties. There is foam padding to seal in the light. The scrap of duct tape is left over from an old diffuser design. Zip-ties are threaded thru the holes and around the stem of the flash heads. These hold the diffuser to the head very firmly.
C. The T-shaped pattern that was cut into the back of the bowls, plus the accessory holes.
ImageTwin flash with new diffusers by Mark Sturtevant, on Flickr

D. The front foam layer is removed to reveal an inner foam layer. The entire interior is covered in shiny HVAC tape.
E. Full interior view, showing the heart of this whole design which is a wedge-shaped deflector suspended in front of the flash head. The deflector is shaped out of card stock paper, and covered with HVAC tape. It is sized to more than eclipse the flash head when seen from the front. The idea here is that no light from the flash can get to the subject without reflecting off of HVAC tape. Hard to see, maybe, but the deflector is held in place with “spider vanes”, much like how a secondary mirror is suspended inside a reflecting telescope. It does not touch the flash surface, and yet its held firmly in place.
F. Schematic showing the deflector. Note that all 4 sides are angled to reflect light away.
G. Schematic showing the overall diffuser design again.
ImageSecret interior design of diffuser. Shhhh. by Mark Sturtevant, on Flickr

Lets see how this works!
All of these were focus stacked by hand from a small number of pictures. Only the last one was done indoors in a staged setting. Other than stacking, only light editing was done (cropping, unsharp mask), to better show what I get from this current rig.

Pink ladybug. This one is dead, having been parasitized by a tiny wasp. I will post more on that later.
ImagePink ladybug by Mark Sturtevant, on Flickr

Cute little tree hopper. I see these on goldenrods. This is a male, I think, and i suspect the pattern on the rear end is a "false head". There are tree hoppers that try to fool predators into mis-identifying where the head is.
ImagePlant hopper stack by Mark Sturtevant, on Flickr

Jumping spider. This might be a new species for me.
ImageJumping spider stack by Mark Sturtevant, on Flickr

A tortoise beetle. Note the "teddy bear" markings.
ImageTortoise beetle by Mark Sturtevant, on Flickr

"Studio" shot of a Chrysomelid beetle. The picture on the left is taken at one stop greater flash power than the picture on the right. I think the super bright reflections on the thorax came from the modeling light I was using.
ImageRed chrysomelid comparing flash power by Mark Sturtevant, on Flickr

Known issues in this design:
1. One usually gets two highlight areas rather than a single one. This is especially noticeable in eyes. I always get two very distinctive bright spots in very shiny eyes like the spider eyes shown above. I've wondered if this is an artifact produced by the eye lens itself, where light reflecting back from the interior of the eye is focused by the lens of the eye.
2. I wonder about the shape of the bowls. The swooped, curvy shape might mean that more light comes out from around the center than from the periphery. Designs to try later would be either hemispherical bowls, or straight sided cones. Not sure where to go with that.
3. I need to work on more 'frontal' lighting. One can see especially in the ladybug and the Chrysomelid beetle how the insect parts facing the lens are rather shadowed. So maybe I should try some kind of reflecting baffle in front that hangs down alongside or below the lens.
Last edited by MarkSturtevant on Sat Jun 26, 2021 3:19 pm, edited 1 time in total.
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Re: Refllector bowl for test shots

Post by rjlittlefield »

MarkSturtevant wrote:
Sat Jun 26, 2021 1:19 pm
1. One usually gets two highlight areas rather than a single one. This is especially noticeable in eyes. I always get two very distinctive and bright spots in very shiny eyes like the spider eyes shown above. I've wondered if this is an artifact produced by the eye lens itself, where light reflecting back from the interior of the eye is focused by the lens of the eye.
I expect what's going on is much simpler than that. The usual case is that the surface of the eye is just acting like a convex mirror, reflecting a much reduced image of the environment around it. That environment has two very bright areas -- one per flash head -- so the reflection shows two very bright spots at the corresponding positions.

See for example the reflections of my face and the surrounding room, in the spider eyes at viewtopic.php?t=13636 . Those two rectangular bright spots are the overhead fluorescent fixtures on the ceiling, which in that case I had used as the primary illumination with an exposure of 0.6 second, ISO 200, effective f/20.

Much can be learned by photographing a shiny metal ball instead of a complicated insect. What you'll see in the ball is exactly the pattern of light that the subject sees, geometrically warped into a fisheye.

Here is an example that I shot on a whim a couple of days ago, using the ceiling of my project room as the reflector for two studio strobes. Both strobes are aimed at basically the same spot of ceiling so there's only one bright area. You can also see in the reflection three overhead fluorescent fixtures. Those were turned on while the picture was taken, but were not producing enough light to show up as particularly bright given the exposure of 1/200, f/16, ISO 100.
IMG_0394.jpg

If you run a similar experiment with your own equipment, using an f-stop that is dark enough to prevent blowing out the brights, you can get a very good idea of how the light is coming out of your flash head modifiers. Be warned: if the diffusers leave hot spots, you may need to stop down very far and or drop flash power a long ways to prevent blowing out the brightest parts. If that happens, of course it will be telling you something valuable too.

--Rik

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Re: Refllector bowl for test shots

Post by Lou Jost »

I think it would be worthwhile to try to eliminate those double highlights. Though they can sometimes occur in nature, they still seem to scream "set-up" to me, and that takes something away from the photo. However, a viewer who is not a photographer may not "read" the photo this way.

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Re: Refllector bowl for test shots

Post by MarkSturtevant »

Lou Jost wrote:
Sat Jun 26, 2021 4:19 pm
I think it would be worthwhile to try to eliminate those double highlights. Though they can sometimes occur in nature, they still seem to scream "set-up" to me, and that takes something away from the photo. However, a viewer who is not a photographer may not "read" the photo this way.
The simplest way toward solving that is to aim one light directly overhead, and at close range. The other light can be aimed elsewhere or turned off. But this accentuates the reduced frontal lighting as you can see. A front reflector could help fix that.
RedChyrysom1Light.JPG
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Re: Reflector bowl for test shots

Post by iconoclastica »

The number of possible lightings are greater than can be enumerated here. But in my philosophy, the core essence is not "how to avoid unwanted reflections", but "choose which reflections I want to see in the result". Admittedly, this is harder in the field than in the studio (yet not impossible).

The simple situation is this:

Hunter &al (2007) fig. 6.1
Hunter &al (2007) fig. 6.1
Any bright light within the 'family of angles' will be visible on the subject, depending of the surface either as bright spot or as specular highlight. The simplest options here are either to fill the entire FoA with a large softbox. The subject then will look like if photographed beneath an overcast sky. Or to move the light source(s) outside of the FoA.
Partially covering the FoA with a softbox may give a 'precious' effect: commercial pictures of smartphones are nearly always done this way, with the edge of the reflected softbox neatly following the screen diagonal.

In case of a hemispheric subject, such as the beetle or a metal ball, the situation is essentially the same, only the FoA much larger:

Hunter &al (2007) fig. 6.29
Hunter &al (2007) fig. 6.29
The subject is excellently explained in Hunter, Biver, & Fuqua (2007): "Light – Science & Magic. An Introduction to Photographic Lighting", Third Edition. You might even find it as pdf on the web.
--- felix filicis ---

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Re: Reflector bowl for test shots

Post by MarkSturtevant »

iconoclastica wrote:
Sun Jun 27, 2021 5:54 am
The subject is excellently explained in Hunter, Biver, & Fuqua (2007): "Light – Science & Magic. An Introduction to Photographic Lighting", Third Edition. You might even find it as pdf on the web.
Here is a short review of this book on YouTube. Its worth watching. https://www.youtube.com/watch?v=bAbTV5hkzn8
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Re: Refllector bowl for test shots

Post by Dalantech »

I have been using a twin flash in a key and fill configuration, like a portrait photographer, for almost 15 years. One flash head at roughly the 12 O'clock position (the key) and the other at roughly 3 O'clock (the fill). Here is a video of the rig with an older diffuser set. The set I currently use is a little larger, but they are pretty much the same.

I am not using the Kaiser adjustable flash shoe to elevate the key anymore. It can cause the shadows to get crushed on the opposite side of the fill and has a tendency to throw E-TTL metering off. As an added bonus if the subject is on a flower the key will fire straight into it causing the flower to act like a reflector and a lot of colored light gets pumped up under the subject. It is also easier to get the specular highlights to blend together if the two flashes are connected directly to the Canon flash mount. Glossy black surfaces have been my kryptonite, but this is how I am currently rendering them:

ImageWasp by John Kimbler, on Flickr

Light can be either hard or soft, specular or diffused. If the light source is large relative to the subject then the shadows will be soft and the line between the light and shadow will not be well defined (soft light). If the light source is small relative to the subject then the shadows will be dark and the line between the light and shadow will be well defined and easy to see (hard light). A large light source can act like a point source (a small light) if it is far enough away from the subject. Likewise a small light source can act like a larger one if you get it close enough to the subject.

If the light is specular (not well diffused) there will be a hot spot in the light that the subject sees and the specular highlights will act like true mirrors and return the color of the light source and not the color of the underlying specular surface. The end result is a loss in detail, both color and texture. If the light is diffused (even across the surface of the diffuser) then there will be detail and color in the specular surfaces. Note: Diffusion can be influenced by the distance between the light source and the subject. Get a well diffused light source far enough away from the subject and the specular highlights will become harsh.

In a studio, using studio light modifiers, there is usually enough room for the light from the flash to spread out before hitting the final diffusion surface -the light source (the light that the subject sees). So the only thing you have to worry about is the distance between the light source and the subject, and as the distance drops the light quality gets better (softer and more diffused). But for field macro it is difficult to get the light from the flash to spread out, in the short distances that most of us are working with, before it hits the diffusion surface that the subject sees. The light ends up being soft/specular: The light source is soft because it is large in the subject's field of view (so soft shadows), but due to a hot spot in the light source it is acting like a point source and detail (color and texture) in the specular areas is lost. One way to test your diffusion is to shoot something reflective and look at the specular highlights. There should be color and texture in the specular areas and you should not see the color of your light source. This is my worst case light quality because it is a 1x shot and the working distance is 4"

Image

Note the color and texture in the specular reflections. As the magnification increases the working distance drops, the flash heads get closer to the subject, and the light quality improves.

2x:

Image

3x:

Image

The "trick" is to find a diffusion material that will force the light to spread out and not just block it. Several layers of 1/4 stop white China silk scrim fabric is what finally worked for me. For the most part you cannot avoid specular highlights but there should be color and texture in the specular reflections no matter what light source you are shooting with. I have seen a lot of macro shooters using harsh noon day sunlight and losing a lot of detail because the specular surfaces all have the same color as the sun.

Footnote: I kinda make it seem so simple with such a short forum post. In truth it took me an embarrassing long time to wrap my head around diffusing a flash in as short of a space as possible, and several years of experimenting with different materials. Got so burned out making new diffusers to try out yet another idea/material I eventually built a set out of Legos so I could easily take them apart and swap out the different diffusion layers. This post literally represents almost 15 years of work diffusing a macro twin flash and I did not cover how the angle between the light, subject, and sensor can influence the amount of texture detail that can be captured. Not an easy subject to say the least.

ImageGecko on a Leaf by John Kimbler, on Flickr

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