I need your help

[CSIJon]

Hello all, this is my first post. I am a Forensic Specialist (basically CSI). I use a camera for many different scenarios. I have had a good bit of training on photography but most of it is crime scene photography. One of the things we have to do is to photograph fingerprint and shoe impressions. We do this in RAW on a tripod at 90 degrees to the subject. My question is that I have been told different things on this. I was told that to get a true 1:1 photo your lens had to be set at 55mm, then told 55mm with and extension tube; B & H told me not a 60mm lens will give you a true 1:1 ratio. I have also seen that some macro lens say 1:1 with 100mm focal length. We have to have it at true 1:1 so it can be compared. I believe (not 100% sure) that you can calibrate with Photoshop if close, but I just want to get to the truth without using Photoshop. If this is the wrong thread I am sorry. If anyone can help it would be great. Thank you and look forward to exploring this forum much more.
CSIJon

 

[Big Mike]

No need to post the same question in different places.