specimen photography

My colleague has corrected me. The above photo was taken with the lights pointed away at a 45 degree angle pointing into the diffuser umbrellas. The light box as set at half.

Lighting looks flat to me. I'm 90% sure you need better lighting. With this type of a shot maybe consistent lighting might be better.

you should post this topic on the lighting section of the forum. They should have much better idea on what you will need.

which 50mm lens are you using?

Consider the macro lens offered by canon. It is the F2.5 version. Very low distortion, though some of what you are seeing is due to perspective. A longer focal length (70 or 85mm to name a few) will be needed to fill the frame with your specimens while being further from your subject.

This kind of work is my bread & butter and would echo what some have suggested, ie. a macro lens. If you have adequate working distance a 100mm macro is the preferable choice but a 60mm would do well. You also need a smaller f-stop, f11 or f16 would be optimal, at a minimum f8. To achieve this you will need good lighting, I would use electronic flash and there are many options out there.

Fidlina wrote in post #12426725
The distortion happens most noticeably in the ventral view. The beak does not look flush with the color bar.

Did you consider raising the ruler/color bar to the level of the beak? That would reduce some perceptual distortion if the size of the beak is critical.

joedlh wrote in post #12428369
Did you consider raising the ruler/color bar to the level of the beak? That would reduce some perceptual distortion if the size of the beak is critical.

For this kind of work you dont want that it look like OK, this is scientific recording.

Gizmo1137 wrote in post #12427837
This kind of work is my bread & butter and would echo what some have suggested, ie. a macro lens. If you have adequate working distance a 100mm macro is the preferable choice but a 60mm would do well. You also need a smaller f-stop, f11 or f16 would be optimal, at a minimum f8. To achieve this you will need good lighting, I would use electronic flash and there are many options out there.

Here we go! +1

Fidlina...looking at the exif data:

Camera Maker: Canon
Camera Model: Canon EOS 5D Mark II
Lens: EF50mm f/2.5 Compact Macro
Image Date: 2011-05-04 12:12:05 -0700
Focal Length: 50.0mm
Aperture: f/29.0
Exposure Time: 0.017 s (1/60)
ISO equiv: 200
Exposure Bias: none
Metering Mode: Matrix
Exposure: Manual
Exposure Mode: Manual
White Balance: Auto
Flash Fired: No (enforced)
Orientation: Normal
Color Space: sRGB
GPS Coordinate: undefined, undefined

Many would suggest that f29 is too high for good digital images. f11-f16 is usually recommended for best results.

I would add lower the iso to 100 and up the shutter speed to compensate for any vibrations.

Macro lenses are noted for having an extremely flat field...ie the resolution does not diminish as you move from the center to the edges.

Darwin put the Finch beak first! This should be nearer the center of the image for best rendition.

I would also suggest that you run a perpendicular reference line up to the tip of the beak similar to a tee square.

Altho your scale is different, you should also be aware of other museum's problems in digitizing art work, see here: http://www.unicorns.co​.za …o-the-aid-of-the-met.html

Good luck, Paul

l7s4 wrote in post #12450119
Macro lenses are noted for having an extremely flat field...ie the resolution does not diminish as you move from the center to the edges.

Id non est, I'm afraid. Flat field relates to corrections for geometric distortion, not to resolution.