The problem with taking photos of insects at high magnification is that you're always fighting depth of focus - the closer you get, the less is in focus in front and behind the point you focus on. The traditional way to help is to use a small aperture but this actually causes overall fuzziness caused by diffraction and at higher magnification you just can't get an f-stop small enough. This is where photo stacking comes in and the theory is pretty simple - just use a normal f-stop and take consecutive photos while stepping the camera on a rail. Then get some clever software to take all the focused bits and combine them into 1 photo that looks impossibly well focused!
Just to whet your apetite here is a nice one by my friend Malcolm Storey (http://bioimages.org.uk):
All you need is a basic dSLR (Canon EOS 1000D is fine at 10 megapixels) and the lens should be fairly good quality but need not be too expensive - I picked up a Nikkor EL 50mm f2.8 and a Schneider Componon 35mm f4 for between £15 and £25 - enlarger lenses work really well when reversed. Then I just bought a bellows; a macro-rail; some adaptor rings to link it all together; a pokey flash gun that can be adjusted really low; and a remote shutter release cable ... all from China. Total cost, about £300-350 depending on how good you are on eBay
Here are a few photos of the setup: 
1000D + Nikkor EL 50mm f2.8 by Cheburashka, on Flickr
1000D + Nikkor EL 50mm f2.8 by Cheburashka, on Flickr
With a setup like that you can get photos like these:
Sarcophaga (Heteronychia) haemorrhoa (male, genitalia, x4) by Cheburashka, on Flickr
Linnaemya picta (male, genitalia, x4) by Cheburashka, on Flickr
Actia sp. (x3.5) - French Guiana by Cheburashka, on Flickr
Chrysocosmius aurata (male, head, x4) by Cheburashka, on Flickr
Prosena siberita (female, head, x3) by Cheburashka, on Flickr
These are all absolutely tiny subjects - 5 millimeters across at the best - but you can see plenty of detail and the subjects have an almost 3D quality. These have all been reduced by quite a lot for Flickr (I don't have a Pro account so am limited to 1024x76
... the higher resolution versions are even better Callibrating lenses and how long it takes to do a stack
You have to start by working out which f-stop(s) give you the best clarity on each lens - they all differ. Just take photos of the same subject - choose something with lots of fine detail and take the shots on macro. When you examine the pics closely you'll see that usually the ones at f5.6 or f8 (for my Tamron 90mm SP lens) resolve the greatest detail. Then you experiment with step size and just choose the step-size that gives you no out-of-focus bits on the finished result ... you can work out depth of focus using some complicated maths but I just did it with trial and error. I also worked out the magnification on the sensor the 'easy way' by taking lots of photos of a ruler at different bellows extensions - then looking up my sensor size in the manual and just working out the ratio to get the magnification If you punch these into Excel you can produce a graph that shows you, for each lens and for each bellows position, what the magnification will be. Once you understand how your lenses perform then you can just write this down and stick it somewhere on the wall to refer to in the future - you don't have to repeat it any time.
I do each stack manually so I literally have to turn the knob on the macro rail (moving the camera <1mm - not too hard with practice) before each shot and press the shutter release. My stacks are usually between 20-30 photos but it depends on how deep the subject is and how deep your depth of focus is. I work out exposures manually too - just by guessing the opening values, taking photos and looking at the histogram and the end result.
My PC has an Intel Core i7 CPU (@2.80GHz) with 4GB RAM and Windows7 ... and it will stack the photos in about 2-3 minutes but, to be honest, I have never timed it - it is fast enough for me to set up the next subject and it's ready. Then I just drop the end result into PhotoShop and do my usual stuff - adjust levels, brightness, crop it and sharpen.
From start to finish (assuming not much dust removal in PhotoShop) it probably takes 30 minutes to come out with a finished photo but I get wrapped up with the whole process and I tend to be fiddling around looking at other specimens and working out what I want to do next so it is hard to judge. It certainly isn't a particularly time consuming process but it depends how much of a perfectionist you are ... and I'm not very Once you're set up you can get on a roll and plough through lots of subjects in an evening.
You can automate the stacking process, if you buy a very nice piece of kit called a StackShot ... but you'll be forking out about £500 when you have paid the import taxes and shipping
Software and other things ...
I use a software package called Zerene Stacker but there are a few out there that will do the same effect, like Helicon Focus & CombineZP. The latest versions of PhotoShop also have some form of stacking in them too, I believe. There are quite a few people out there doing stacking and they all seem to have their favourite software packages but for me Zerene was the best choice because it works better 'out of the box' when dealing with bristles - the other packages always left artifacts or strange halo effects behind, which you'd then have to PhotoShop or retouch. CombineZP is freeware but the others you have to pay for but they both have 30-day demos so everyone can have a play if they want to
To be honest, I am learning fast (I've only had the kit for a month) but there are some guys out there who are doing incredible work with stacking. If you want to see some really amazing stuff have a browse on the PhotoMacrography.net website (starting with the admins award page). There are some amazing guys like Mathias Lenke, Craig Taylor, Nikola Rahme and John Hallmen ... to name but a few. I don't want to do myself down because I think I am doing pretty well and actually achieving more than I thought I would at this stage and with limited equipment ... but those guys give me a lot to aspire to
Photography can be really expensive and you can throw vast sums at work like this if you want - commercial stacking systems that museums use can cost in excess of £20,000. But I have done my work with very simple equipment that is within the reach of most people
I am uploading the best pics to my Flickr account so just watch that ... but I probably won't be uploading much until the New Year because my house is in chaos after a flood (pipe in the loft broke!) and so it's all a bit too humid and dusty at the moment
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