lens and flash combination

[paul_j_c2000]

Hi everyone i have had a 10d for sometime and love it ,using it in daylight hours recently i have found conditions in woods etc to be to dark for satisfactory pictures of fungi etc so have bought a 550 flash .my question is what would be your choice of lens to cover the range of the flash in various situations,sometimes it is nice to get a real close up ,others look better with surrounding detail,the flash can zoom up to 105 mm,does this mean the camera can auto focus with a 100 mm lens?,what happens if i use my 300f4is,i am not worried about the cost i would just like to get the best combination to take out in the evenings any help always appreciated thanks paul

[Andrew03]

Hi Paul
Too true it can be dark in woods making photography difficult, but using the 550 on the camera will give harsh shadows - better to try and bounce the light off a reflector, or better still, not use flash - best use a tripod to allow you to use a slower shutter speed. So step 1 - use ISO 400 (or less), step 2 set an aperture which gives reasonable depth of field (around 5.6 i'd guess - experiment) and step 3 if the shutterspeed is close to or slower than 1/focal length then use a tripod.
The camera will autofocus with any lens with a maximum aperture of 5.6 or bigger (ie lower f no). The flash will work with any length of lens (except ultra wide angle - will still fire but will not cover the whole view). I don't think the 300 f4 is really suitable for fungi - you'll need a fast shutter speed. Better to use something around 50-80mm - the 50 mm f1.8 is pretty good for fungi, or else the 100mm macro.
The very best thing is to practice/experiment and see which results you like best!
Andrew