How to get read of reflections when taking pictures of electronic circuit boards?

simplex

simplex

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How to get read of reflections when taking pictures of electronic circuit boards?

I have to take pictures of mainly custom made electronic circuit boards that have many shiny cooper traces and electronic components. I have some success in getting relatively good photos only if the light of the flash strikes the printed circuit board at an relatively large angle, say 45 degrees. Each time I try to take a picture directly from above the circuit, I get all kind of reflections that make the image of little use.

What do I have to do to get rid of those reflections, and get a clean image, while taking pictures of the type front view?
 
You need to do two simple things.
1. Position the light so that the reflections don't reach the lens, which is pretty obvious when you think about it, because the angle of reflectance must always equal the angle of incidence, just as a snooker ball must always bounce off of the cushion at the same angle at which it hits it
2. Use a very large light source, as close as possible to the subject, so that any specular reflections (reflections of the light source) that reach the lens will be diffused, and will show as large light areas not small blindingly bright ones. All is explained in this basic tutorial http://www.lencarta.com/studio-lighting-blog/12/controlling-specular-reflections/#.V6jmPq0W4g5
 
The only light I have is the flash of the camera. I use a pocket camera. The circuits are in the most unexpected places. In my case it is not practical cu carry with me lights and other equipment all the time, not even a tripod.
 
In that case, nobody can help you, sorry
 
Take the shots at an angle, it's all you can do.

You canny change the laws of physics captain.
 
As you've discovered, and Garry has explained, you need to get the flash off-camera and at an angle to the subject. That can be done quite easily with a separate flash gun and trigger attached to the camera's hot-shoe, but if the flash is fixed and the camera doesn't have a hot-shoe, you're stuffed.
 
HoppyUK said:
...you need to get the flash off-camera and at an angle to the subject. That can be done quite easily with a separate flash gun
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This is an interesting and practical idea. I will try it with a professional camera (which is not mine).

FishyFish said:
Could you use a bit of reflective material to bounce the flash and another piece of reflective material to redirect it back to the circuit board? Some bits of cardboard coated with tin-foil would probably do the trick.
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I will try your suggestion.
 
simplex said:
This is an interesting and practical idea. I will try it with a professional camera (which is not mine).
Click to expand...

It's the most obvious and best option. When you get to try it, if the light is much brighter on the flash side, put a piece of white card on the opposite side to bounce light back again and it will even-out things out.

I will try your suggestion.
Click to expand...

This is a way of getting light from the on-camera flash to an off-camera position, with a system of reflectors. Fine in theory, but could be much more difficult in basic practical terms.

The torch idea would also work in theory, though brightness will be low, demanding long shutter speeds. Therefore a tripod will be needed. Colours are unlikely to be 100% accurate, but after white balance adjustment in post processing, they'll probably be good enough.
 
juggler said:
This might be one of the rare cases where an LED video panel would work acceptably well - hand-holdable, slim enough to get into small spaces, large enough to be somewhat diffuse and most importantly off the camera.
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Good idea! Not sure why I didn't think of that LOL And in this case, ie at close distance, it should be bright enough for hand-holding the camera. Sorted :thumbs:
 
Try it and see. The problem might be the reflection from the direct flash. I have done this loads of times with a compact camera's tiny flash.


Steve.
 
Steve Smith said:
Try it and see. The problem might be the reflection from the direct flash. I have done this loads of times with a compact camera's tiny flash.


Steve.
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It will still be a reflection from a direct flash from the wrong angle, it will just be slightly more diffused - it will not and cannot help.
 
frod said:
is this not a job for a polariser?
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No, it's a job for the right size of light from the right angle.
A polariser won't work at all on the metal bits, and in any event where it does, work, it only works within a narrow range of angles
 
As Garry says, polarising filters only remove reflections (off anything except bare metal) at a very limited range of angles - at between 30-40 degrees to the surface (Brewsters Angle) and with total removal only at two or three degrees within that range. The common belief is 'polarisers remove all reflections' because they work so well on popular subjects like water in landscapes, and foliage. But that's because reflections off water are often at just the right angle, and with shiny foliage, a lot of leaves etc will also coincidentally fall at the right angle. At the same time, this degree of rotation often darkens blue skies too, if the angle to the sun is right.That's why landscapers love them.

An easy test that will show everything about reflections and polarisers, is to photograph a dark shiny car shot at around 3/4 from the front, so the doors and bonnet/roof are at 30-40 degrees. Rotate the polariser and reflections on the bonnet/roof will vanish, but will be unaffected along the doors. Then rotate the filter a quarter turn (90 degrees) and reflections on the doors will go, but reappear over the bonnet - you can't have both. Then move backwards and forwards towards the car, and that will change the angle to the doors. As you move, so the 30-40 degrees sweet spot will move along the side too. Actually, you don't need to take any pictures or even have a camera - just look through the filter :)
 
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Reading this thread it'd be easy to believe this is a complicated issue.

It really isn't, it's all based on one simple rule of physics, light will bounce off an object at the same angle it struck it, like a snooker ball off a cushion.

The OP is shooting straight on with onboard flash, the first simple solution is to shoot at an angle, where the reflection from the onboard flash will then not bounce back to the lens.

For a more elegant solution, allowing any camera angle, the option of using a cheap LED light panel would be cheap and easy.

For absolute precision, a better camera and off camera flash solution is preferred, but that's lots of spending and learning that's not really necessary for a few casual shots.

All the talk of polarisers and diffusers is muddying quite a simple issue.
 
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mike weeks said:
This thread is also becoming polarised into;

1. those that know what they are talking about
2. everybody else

Mike
Click to expand...


To be fair, if everyone thows in the ideas that are wrong, and people take the time to explain why they are wrong, then that's not a bad thing. Many of the ideas suggested are possibilities for other lighting situations, not this one.
 
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