Photographing Reflecting surfaces for textures

[Marcel]

For photographing reflective object a 'lighting tent' is useful. Here are some examples of commercial versions:

http://www.stevesphotoshop.co.uk/photo_light_tents_cubes.html

If you don't want to spend cash on it you can always rig something up yourself with some plastic pipes and old sheets.

http://www.pbase.com/wlhuber/light_box_light_tent

To avoid your camera being reflected you only stick the lens through a hole in one of the sides. A curved floor/background will help to avoid a seam in the back of the picture.

To get the reflection looking nice you should experiment with gradients or dark areas, just like you would in a 3D application.

If you goal is to get nice textures of the radios you could try to photograph them in HDR and tonemap them. I haven't tried this myself but I've seen examples of textures photographed like this which looked really good. The tonemapping allowed you to make them much more 'flat' than a single picture.

[Heerko]

Thank you very much for your tip! Just bought a lighttent from http://www.lighttent.eu. I am very anxious for the results.

You think HDR will help in making the texture more flat? Can you maybe give me some insight why that would be?

Thnx again!

[Marcel]

You think HDR will help in making the texture more flat? Can you maybe give me some insight why that would be?

Sorry, I wasn't very clear :). With 'flat' I didn't mean that is has less distortion, but that the lighthing is more even. Here is an example from "The HDRI Handbook":

http://old.cgtextures.com/.Temp/tonemapping.jpg


As you can see in the example in the book you can remove much of the lighting and shadows with the tonemapping, so you only end up with the pure color.

If you have a SLR just set your camera to 3 shot AEB (Auto exposure bracketing) and it'll take 3 exposure (-2 stops underexposed, correct exposure, +2 stops overexposed).

You can create the HDR using 'Merge to HDR' in Photoshop or in Photomatix. Photomatix can batch process (also in the trial version) which is a huge timesaver if you have to take a lot of pictures.

The tonemapping in Photoshop is pretty basic, the free program Picturenaut probably gives better results:

http://www.hdrlabs.com/picturenaut/

How many radios do you want to photograph, and are you going to model them all?

[Heerko]

Great! Very interesting. I did some experiments with HDRglobes before (using a Christmas ball and HDRshop) And I read some tutorials before where they edited photographs 'HDR like' to bring out details in windows and shadows etc. But I never heard of Tonemapping.

The pictures you provide look kinda bleached (or in dutch: flets). Is that the result you get from tonemapping? Wont you get wrong colors out of it that way?

I looked at the tutorials at hdrlabs.com (nice link!), they have a bit about tonemapping too. But don't know quite what to do for creating good textures.

I have 5 radios (actually CB Radio's (27 mc bakjes) which we are going to model.

[Marcel]

Tonemapping is relatively new, and not something you often use in 3D (yet?). I hadn't heard about it either until I started photographing HDR skies.

The picture is a photo of the book, I think the camera flash made it a bit more 'flets' than they actually are (I was too lazy to start up my scanner ;))

The tonemapping can remove the larger lighting differences from the image, just like you would with the 'High Pass' filter in photoshop. That will make the colors more uniform, but that's exactly what you want in most cases: a red car is uniformely red under perfect lighting conditions.

Show us some results when you have got your lighting tent, I'm very interested!

[Heerko]

I will post some pics when its in. I'm currently looking at greycards for whitebalancing etc. Have you got experience with that?

I'll try the tonemapping too, but not sure what to do, automate it? Or is it handwork? Brush bits out etc?

I'm thinking of putting the lighting tent on a perspex board, which is hold by transparent plastic cups or something like that. And underneath that a white table. So some light will also be reflected from underneath to get even softer light.

[Marcel]

I will post some pics when its in. I'm currently looking at greycards for whitebalancing etc. Have you got experience with that?
I have a QpCard 201, which can recalculate whitebalance using a special program:

http://www.qpcard.se/BizPart.aspx?tabId=31&prod=3&catId=1

To be honest I haven't used it much. I'm not shooting portraits so the white balance is not that important for me. Usually setting it to the correct WB preset on my camera is enough.

If you want a free greycard you can also go to the DIY store (Dutch: bouwmarkt) and get a color some sample cards from Flexa. They have some colors that are pretty much 100% neutral gray. (Flexa paint number ON.00.50 for example)

I'll try the tonemapping too, but not sure what to do, automate it? Or is it handwork? Brush bits out etc?
If you use PictureNaut you just play with tons of sliders until you like the result. Like I said, I've only used it for skies so I can't tell if the extra effort is actually worth it for normal textures.

I'm thinking of putting the lighting tent on a perspex board, which is hold by transparent plastic cups or something like that. And underneath that a white table. So some light will also be reflected from underneath to get even softer light.
Good idea! Is it a commercial project? Because you are putting quite some effort into modelling those radios :D

[Heerko]

Hmm just ordered a greycard, ah well wasnt that expensive but I like the Flexa sample card idea :D

I should have waited for your reply before ordering, cause the QPcard looks very nice.

This is a commercial project indeed, but prob. not worth all the time in preparation I'm putting into it now, but I like to figure out these things, very instructive and fun.

[Heerko]

Today my lighttent, daylight lamps and greycards came in.

Tent open:

http://www.heerkogroefsema.nl/photos/TentOpen.jpg

Tent closed:

http://www.heerkogroefsema.nl/photos/TentDicht.jpg

I photographed it first with the tent closed with the camera popping through the splithole. Bacause the camera opened the split, you could see a dark reflection of the split, so I put 2 white A4 papers around the lens of the camera. Now you can still a dark reflection of the lens, but I can't hide that, just like the optic nerves "black spot" in the human eye. :)

When I photographed this close, I got some severe lens distortion. Corrected that a bit in Photoshop as you can see in the top and bottom of the picture. But it cant hide the bulge in for example the brown knobs. So this photo sucks as a texture.

http://www.heerkogroefsema.nl/photos/InTent.jpg

So then I had to open up the tent and take a picture from some more distance zoomed completely in so that there would be no distortion.

http://www.heerkogroefsema.nl/photos/OutTent.jpg

As you can see the photo is now a lot darker. I guess because there is no white lid to reflect, and no white lit to refelect light.

As you can see there is also quite some color difference though I used a greycard. I used levels in photoshop along with the grey eyedropper. But it seems the level eyedropper takes a 1px sample instead of an area. That will never give good results, cause when I zoom in to my greycard you can also see red blue and green pixels along the grey one. So I need an area sample.

I'm gonna try shooting RAW and import it into Aperture and have a look at the eyedropper there.

Do you in the mean time have any tips. Anything wrong on my setup etc? Or in my usage of the greycard? Or the way I photograph? I use the automatic settings.

[Marcel]

Nice setup! The textures are already looking fine!

How much Watts are those lights, and where did you get them?

About the greycard and noise: you can do three things:

- keep picking until you like the colors you see (and use alt-L on the other images to repeat the Levels operation)
- apply a gaussian blur to the part you sample to get rid of the noise
- photograph at a higher ISO

I usually try to get the ISO down to at least 200, preferably lower (100, or even 50). You will need a lot of light for this though! Maybe you need to move your lamps a bit more towards the camera so the light strikes more from the front.

If you have an external flash that might also help, external flashes give an awesome amount of light. Or on a sunny day you could also go outside with your whole setup, daylight is much stronger than artificial light.

To get rid of unwanted noise I also use the Noise Ninja plugin a lot, it can really help to make textures look cleaner.

How far is your camera from the radio now? Like you observed yourself the open end of the light tent is showing up in the reflection as a dark spot. Since the front of the radio is facing exactly forward you can probably fix this by hanging a bedsheet in front of you camera (no need to create an elaborate tunnel) and sticking the lens through a hole.

[Heerko]

Thnx :) I got the lamps at the same place I got the tent from: www.lichttent.eu

I got the 85 Watt Daylight lamps. I believe the actual output is higer than that (in comparsion to normal bulbs). But its not giving as much light as lets say a 500 watt buildinglamp. But I like the color of the light, or the lack of color in the light actually.

Of course the desk-lamps arent really fit for these bulbs, I guess a lot of light is lost in the wrong directions. I could make a carton with alu-foil. But what a hassle for textures you wont be seeing that good :) I'm being too nit picky.

Before your post I have been shooting a ISO 100 at a distance to avoid lens distortion. In Photoshop I found out if you widen the sample area of the eyedropper tool (in the toolpalette) the eyedropper in the levels will also grow (not too sure though).

I also thought of a bed sheet as you mentioned, I'll do that next time. Dont want to put too much time in this anymore :)

You mention the use of a flash light. I have external flash here. But where should I put that next time? Cause it will give a hell of reflection and hard shadows right? So do you have a setup in mind where you wouldnt have that?

I'll have a look at noise ninja, thnx!

[Marcel]

Thnx :) I got the lamps at the same place I got the tent from: www.lichttent.eu (http://www.lichttent.eu)

I got the 85 Watt Daylight lamps. I believe the actual output is higer than that (in comparsion to normal bulbs). But its not giving as much light as lets say a 500 watt buildinglamp. But I like the color of the light, or the lack of color in the light actually.Nice! I've been looking for those but I only found really expensive ones.

Most things I photographed inside weren't very colour sensitive, so I could just use lots of halogen lights. The downside is that 6 x 600W halogen lights give off a lot of heat ;)


You mention the use of a flash light. I have external flash here. But where should I put that next time? Cause it will give a hell of reflection and hard shadows right? So do you have a setup in mind where you wouldnt have that?Just set it to maximum and bounce the light against the ceiling. The light will reach the light tent from all directions.

Which brand camera do you have? Because if you are using a Canon I have some flash tips.

[Heerko]

I'm using the Canon EOS 350D, bring on the flash tips :D

[Marcel]

From http://photonotes.org/articles/eos-flash/

10) Why does my camera meter in P and Av modes very differently when I have a flash turned on? That’s how EOS cameras are designed to work. P, Av, Tv and M modes all meter for flash in different ways. See the section on “EOS flash confusion (http://photonotes.org/articles/eos-flash/index2.html#confusion)” for details. Here’s the short version, which repeats some of the points made in previous FAQ questions.

Keep in mind that the camera meters for ambient (existing) light conditions and flash illumination independently.

P (program) mode keeps the shutter speed between 1/60 sec and the maximum flash sync (http://photonotes.org/articles/eos-flash/index2.html#xsync) speed your camera can handle. It does this so that you shouldn’t need a tripod, even if light levels are low. It then tries to illuminate the foreground using flash.

Av (aperture priority) and Tv (shutter speed priority) modes set the shutter speed or aperture to expose for the existing light conditions correctly. They then fill in (http://photonotes.org/articles/eos-flash/index2.html#fillflash) the foreground using flash. If light levels are low you will need a tripod to avoid blur.

M (manual exposure) mode lets you set both aperture and shutter speed to be whatever you want. The camera then automatically controls the illumination of the foreground subject using flash.



There a more detailed explanation here: http://photonotes.org/articles/eos-flash/index2.html#confusion

In practice I always set my camera to the M (manual) mode because this way I get the strongest flash. Just set your shutter speed between 1/50 and 1/100 (not higher or your flash cannot keep up) and your aperture between F7 and F10 (your lens will be the sharpest between these apertures). Your camera will complain that the image will be underexposed, but the flash will compensate automatically to get a correctly exposed image.

If you shoot in RAW take a good look at the histogram after you have taken the photo. Sometimes the preview looks great on your camera's LCD, but the picture is completely underexposed. Because your camera auto-levels the preview you don't notice this unless you look at the histogram.

[Heerko]

Sorry didnt see you replied, didnt get a notification by mail :) Thnx for the tips, I'll look into it. And many thnx for helping me out in this thread!

Keep up the good work at CGtextures, great site!

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