Reptile & Amphibian Forums

I recently got a sigma 105mm macro lense. I have taken a few rolls of film in different lighting conditions with various Fstops and shutter speeds, but I am still having major depth of field issues. For example I was taking some pics of some cal kings as they hatched and my depth of field was less then 1/8 inch. If the eye was in focus the nose wasn't... etc. Is there something I can do, or is the problem that I am approaching the limmits of a 105mm in terms of the size of my subjects???? Any advice would be sweet.

This is a limitation of doing macro photography - there is very little depth of field. Most people don't realize just how little there is.

There is a link to an online depth of field calculator below. Play around with it and it will show you how much of your photo should be in focus at a given f/stop for a given lens and sensor/film size.

For example, with 35mm film and a your Sigma 105mm macro lens from its closest focusing distance (12.2 inches) and stopped all the way down to f/45, you get 0.62 inches DOF. And this will give you VERY slow shutter speeds. If you open up a bit to get more light (say f/11) you decrease your DOF to under 1/4 of an inch! At f/5.6 you are down to 4/100ths of an inch.

So the solution is to use a tripod, stop down as far as possible and use extra light (flash) to give you usable shutter speeds.
Online depth of field calculator

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Chris Harrison
San Antonio, Texas

thanks for the advice. Hopefully next roll I'll have something worth posting.
cheers