1 to 1 ratio on printing macros

Blues fan

Does anyone know how to resize a shot to be actual size of the item you are taking a picture of. The purpose of this is for fingerprints. A picture is taken of the print and needs to be printed to its actual size. Can anyone help me out on this?

A friend asked me how to do this and I didn't know so I am asking others that may know. I know he uses a Canon digital rebel but not sure what lenses he uses.

Thanks in advance for any help.

Gil

mercphoto

Blues fan wrote:

Does anyone know how to resize a shot to be actual size of the item you are taking a picture of. The purpose of this is for fingerprints. A picture is taken of the print and needs to be printed to its actual size. Can anyone help me out on this?

A friend asked me how to do this and I didn't know so I am asking others that may know. I know he uses a Canon digital rebel but not sure what lenses he uses.

One, I know nothing about forensic photography. But a few thoughts come to mind.

1) The picture needs to be taken perpindicular to the fingerprint. Be very careful about this.

2) Place a ruler next to the fingerprint so that you have an accurate indication of distance. Include this in the image when you snap the picture.

3) Use Photoshop to crop to a certain size. If you want a 2" tall picture, use the crop tool set to 2" tall, and grab a crop box that measures 2" based on the ruler you have in the frame.

muddyknees

Blues fan wrote:

Does anyone know how to resize a shot to be actual size of the item you are taking a picture of. The purpose of this is for fingerprints. A picture is taken of the print and needs to be printed to its actual size. Can anyone help me out on this?

A friend asked me how to do this and I didn't know so I am asking others that may know. I know he uses a Canon digital rebel but not sure what lenses he uses.

Thanks in advance for any help.

Gil

How much detail do you expect to get? I'm asking because your image is going to be less than an inch on a side, and, maybe I'm wrong about his, but I think typical resolution for photo paper is around 300 ppi, so the image is going to be quite crude. (Unless you're printing to film, in which case you can multiply that ppi by ten or better.)

Anyhow, after photographing an accurate scale into the image, you can calculate what to set the resolution to in the image size dialog in photoshop to get a 1:1 print. Using the highest resolution capture from the DRebel this would be on the order of 4000 ppi assuming you're using a macro lens at about 1:1. (This will be "dumbed down" at the printer to whatever the printer rez is - eg, about 10x10 blocks of file pixels become one printed "pixel"? - give or take whatever factor due to "printer dots or film grain vs image pixels" technicalities?)

(Hope I'm not spewing total nonsense here - anyone else care to agree/disagree/refine my estimate?)

Gary