Distance recommendation for small objects (Coins)

[Nils]

Hello to all of you,

First of all: I've started using RTI's at the End of last Year so my experience is limited. But what I can say, is that RTI's deliver great results on what I could try so far and I am having great fun using the Highlight Method for archeological purposes. This Forum has been a great help for my first steps so far!

Now let's come to my Question:
The manual from CHI recommends 2-4 times the diagonal distance for the flashlight to the object. Now in my case for example, I would have an ancient coin of about 1-4cm in size, the camera at a distance of about 20-30cm. Now if I follow the recommendation of the manual, my external flash would be at about 4cm (extremely small coins)- 12cm(regular coin size) distance from the coin. That not only makes my resulting pictures very bright (even overexposed) but also limits my angles and harms or even destroys the shading. Furthermore I have to be extra careful to avoid my hand/flash being on the pictures.

Because of this, I tried to use a further distance to the object, but I'm not sure what distance to use and in how far that interferes and/or even harms my results.

Do you have any information and/or recommendation for me concerning the light- and cameradistance when shooting small objects, such as coins?

(Camera: Canon 60D
lense: usually a 40mm prime lense)


Kindest regards and thanks in advance,
Nils

[leszekp]

Somebody else can jump in and correct me if I'm wrong, but I believe the 2-4x distance rule-of-thumb is a minimum distance, not an absolute requirement. The further away the light is, the larger the area of relatively uniform lighting, which is a good thing for RTI.

[Nils]

Just for the record, in case somebody else has similar issues:

I made some more tries on smaller objects with light-distances between 20 and 45 cm and all of them had good results. I can't say which results are better, they seem to be very similar.

[cdschroer]

Leszekp is correct, the recommendations are for minimum distances. 2 times really is the minimum for getting good normal data.

 

You can always go longer assuming that you have a powerful enough light to cover the surface you are imaging evenly from that distance.  With small objects like coins, this is not a problem.  You likely cannot tell any difference in results from these 2 image sets.

 

Also a reminder that you want to set your flash (or other light source) for wide beam.  On the Canon older speedlites' that is 24 degrees.  I think the newer ones go to 20 degrees.  The reason is to get even illumination across the surface, so if you get the light from the middle of the beam, that will best meet that need.

 

Carla