Sigma EF-140 macro ring flash - doing the math

[jaybie]

Just a couple of things I would like to get straight

I am thinking of getting the Sigma EM-140 for use with Nikon D40/D5000 and Nikkor 105mm micro lens. The aim is to be able to hand hold as well as use a tripod so I hope it's not too heavy a combination.

The Sigma has a guide number of 14/ISO100 and the D5000 a highest sync speed of 1/200. Using a multiplication factor for ISO of 1.4 for increase from 100 to 200 this would give me a GN of 20. I should therefore be able use f32 at a distance of 0.2m @ 1/200 to give me decent DoF (from a couple of calculations using the formula GN=distance*f number).

Have I got the maths right ?

From the threads I have found here it would appear the the flash is quite versatile though I'm not sure what the modeling mode is.

Also I have not been able to find out what the flash duration is, I downloaded the manual but it doesn't appear to be in there - anybody any idea?

Thanks, JohnB

[Mike Jackson]

The calculations have gone straight over my head but I use the ring flash in combination with my gripped canon EOS 50D and EF 100 Macro lens. I don't find the combination too heavy to handhold and I rarely use a tripod because it's normally insects that I'm photographing.

I normally use the camera in manual mode with 1/125 shutter, ISO 200, f/16 - f/22 and let the flash work out the power required for a correct exposure. I've never had the need to go as narrow as f/32 to get a decent depth of field with insect photography.

[jaybie]

Thanks for the response Mike it is very helpful. My Nikon combination would be a little bit lighter than your Canon set up so I should be OK. I will just need to practice and get used to the balance.

Calculations are fine but nowhere near as good as practical experience.

JohnB

[slimrbp]

Hi,

I use a similar system to Mike, either AV mode with shutter set to max flash synch (1/250) or manual with shutter speed and aperture set.

I mostly handhold my macro images as I find it allows me to get to places that a tripod wouldn't (well not before I had scared off my intended subject!).

I currently use the Canon MT24-EX flash but have used the Sigma on the Canon and it was a nice flash. The modelling mode puts the lamps on so you can see how you are going to light the subject also useful if you are in dingy light and need to see the subject a bit better for focussing.

I tend to shoot between f11 - f16 as I find anything above that and the image tens to soften due to diffraction.

It is worth trying it out at home in controlled conditions so you get used to how the lighting works at various aperture/shutter speed combinations.
I found that smarties or similar were good 'beetles' as they have a slightly reflective surface.

[jaybie]

Thanks for the input Richard, most helpful.

Originally Posted by slimrbp

I found that smarties or similar were good 'beetles' as they have a slightly reflective surface.

Great idea and I get to mop the "beetles" up afterwards

John