Macro shot printing question

[kwhunter]

Silly question but has to be asked: a macro shot scale 1:1, on what side paper has to be printed for the subject to print real size, as shot? The sensor on my 40D is 1.6 crop.
Thanks.

[LordV]

If you shoot it at 1:1 the the image on the sensor is the same size as the subject, so you would need to print it to the same size as the sensor ie something like 22.5*15 mm.
If you shot it with a FF camera at 1:1 you would then need to print it at 36X24 mm

Brian V.

[pturton]

That's correct Brian. Seems the OP wants a thumbnail print. If the 40D was a film camera, a contact print would be as you said, 2.25 cm X 1.5 cm.

If a 1:1 image from a 40D is printed at 10X life size, the print will be approximately 9 x 6 inches (22.5 x 15 cm).

[kwhunter]

Actually, what I need is to print a macro picture at a size that is an exact multiple of the scale of the subject, i.e. 4x6 divided by the size of the sensor.
Not that proficient in PS to know if you can set the magnification to an exact value, or how to do that.
Do you guys know the exact active size of the sensor on a 40D?
Thanks.

[pturton]

Actually, what I need is to print a macro picture at a size that is an exact multiple of the scale of the subject, i.e. 4x6 divided by the size of the sensor.
Not that proficient in PS to know if you can set the magnification to an exact value, or how to do that.
Do you guys know the exact active size of the sensor on a 40D?
Thanks.

Page 181 of the Canon EOS 40D English Instruction Manual :
Spoecifications
...
Image Sensor Size: 22.2 x 14.8mm


To set your screen and print resolutions in Photoshop:

Menu, Edit, Preferences, Units & Rulers, New Document Preset Resolution, Print Resolution - enter value in pixels/inch or cm
Screen Resolution - enter value in pixels/inch or cm

For print resolution I use 240 pixels per inch for my dot matrix printer and 300 ppi for a continuous tone print.

To calculate your screen resolution, divide the pixel width of your monitor by the actual width in inches or cm. If set properly, the image will measure close to the same width & height on the screen as on the print. For example, an image sized for an 8x10 inch print will measure close to 8x10 inches on the screen when menu item View, Print Size is selected. As a double check, do the same calculation for the vertical pixel and physical height of your monitor. If there is a difference from the horizontal resolution, enter the average of these H & V figures.

If you include a scale (steel rule) in the image with the subject, you should be able to get a good grasp of how to print your subject to an exact multiple of the scale of the subject.

[LordV]

If you just want to know what the print magnification of the subject actually is then for a shot taken at 1:1 just divide the print width by the sensor width (ie 22.5mm)

Brian V.