I need to take pictures of my lab samples to compare the different color shades. The samples are very fine dust and the smallest portion is around 5mmx5mm. I have one session to take any photos then I'll have to use/destroy them for further testing.

Basically what I need is good/actual color, and ideally 10x magnification for publication/presentation. Can regular digital cameras do that? Need to be sure coz I only have one try to get it right then no more samples. Anything else I need like background or lighting things I need to be aware about?

Not sure if those are the correct terms, no experience with photography.

Would appreciate if anyone can give tips or guidance.

can we meet up one day and you show me a sample? sound like you need a microscope instead of a dslr

This post has been edited by guest18: Jul 21 2013, 08:21 PM

Test first. Just use a bit of sugar, curry powder, or whatever you have. Then you will know if that camera is suitable to get the picture you want. Zoom, focus distance, picture quality, etc.

You're right to be concerned about the colour. All digital camera have auto white balance, which changes the colour.

1) turn off the auto white balance, and use the manual option instead. Calibrating it with the white background you use will be a good idea.

2) use a large white background for the photos. The same exact white background. For example 10 sheets of A4 photostat paper (because one layer is not enough, and whatever is underneath will show through). Also note that not all "white" paper is the same colour. And they may not be exactly white. But what's important is that the "white" on every picture is the same.

3) use the highest resolution available on the camera. Don't zoom in too much. Make sure most of the picture is of the white background, with the sample covering not more than 10% of the picture. You can crop the picture later in your computer.

4) if you have a standard colour scale to compare the sample against, put that on top the paper, and make sure it is in every picture. If you don't want it shown, you can put it to one side and crop it out later. If you don't have one, you can make one by printing squares of a few colours like white/black/red/green/blue/cyan/magenta/yellow. If you know in advance, the samples are likely to be of what colour, you can use somewhat similar colours.

These will let you compare the pictures later to each other and see if the colour balance is correct.

5) have plenty of light. Use white table lamp. You will need a few (at least two, more is better). Otherwise the picture will appear to be unevenly lit. Don't use flash.

6) watch out fo specular reflection. You can just move the lights and camera position around, until you get the result you want. Keep them in the same position while you take the rest of the photos of the other samples.

7) put the camera on a tripod, and move the samples to the camera, rather than the camera to the sample. This will reduce variations in lighting, colour, and density. Put a mark on the white background, so that you place the samples at the exact same place everytime.

8) set the camera to manual mode, don't use auto for shutter speed, aperture, ISO, focus. This keeps everything constant so that the different pictures are comparable.

If I take 100 photos of something on the table with auto-focus on, with the camera on a tripod, and the object being the same distance from the camera; maybe 5 to 10 might be out of focus. You said the samples will be irreplacable. It would be a big problem if you get a few pictures "out of focus" (not obvious on the small screen of the camera, but only visible once you transfered the picture to a computer's large skin).

9) close the window shades, and rely on internal lighting. This help keep things consistent.

10) snap a few pictures of each sample.

There are microscope adapters that attach to the front of SLR cameras. And many microscopes are built for this. Some have a "third eye". With others, you just remove one of the eyepieces, and put the camera there.

Does TS's lab already have one of these?

Thank you for the detailed advice. I think this guide should be good enough for me.

There should be that type of microscope somewhere but they are in another faculty, access will require time and processing.

5mm x 5mm isn't exactly fine.
They're larger than coarse sugar.
If they're really that size, a camera with good enough macro mode is sufficient for presentations.

However if you're looking for quantitative data and you're looking to publish this work... using a digital camera is pretty useless.
Why ?
Inconsistent lighting (colour temperature, position of light source and sample)
Inconsistent magnification
Inconsistent setting (If camera does not have manual mode)
Jpeg (If camera does not have tiff/raw ability)

Now even if you have a microscope, capturing a 5mmx5mm can be complicated if you do not have the right objective. (Recommended 1x, 2x or 4x)
You might be able to barely view it in a 10x objective through the eyepiece, but it'll usually be more zoomed in on a camera.

It's powdered samples of very fine dust, barely enough amount to fill a 5x5mm area. The individual sizes are smaller than 1micrometer.

Photos will only be used to compare color shading, anything else like shapes will get from another method.

sorry just curious.. but why a camera.. why not a spectrophotometer for something scientific..

because you said shapes is another method.

dkk's post is very comprehensive. you should heed his advice.

i'd like to add that you should shoot in RAW format. cameras tend to have their own 'style' in processing photos into JPEG format, which might give you unwanted shift in colours. but i imagine if you're more interested in the *change* in colour, rather than the accuracy of the colour, this shouldn't be a problem.

the idea is to have manual everything (white balance, focus, jpeg processing, etc) so you are in control of the consistency. not many point and shoots can do this. i'd suggest a panasonic LX7 or canon S110 (or even the earlier models LX3 and S95).

if you have a dslr (or plan to get one anyway), you'll need a macro lens.