Comments on Digital Photography, Particularly used for micros
Posted: Feb 24 2010 on LTS forum:
During a recent discussion on Conch-L regarding scanners many comments were made about using digital cameras to photograph shells. I though you might find some helpful.
2/22/10 Responding to a post by David Kirsh about scanners, James Miller suggested:
"Get yourself a decent digital camera! For $150 on eBay you can buy cameras that have built-in flash and macro capabilities that will far outperform your scanner. Scanners are useful, but a digital camera is 10 times better!"
2/22 David replied:
"Jim, I've got a Canon SD 1200 with 10 megapixels. As a handheld camera for micros, it hasn't had results to rival my former scanning. But that might be for lack of a tripod or possibly a higher resolution setting. I'd appreciate if someone can advise me on it. I suspect I'll need to contact Canon's support, which I haven't gotten around to yet."
2/23 Marcus Coltro suggested:
"I 've never used scanners to take pictures as the results cannot compare to any reasonable digital camera. I guess you can use it for a quick photo to use on internet but not for printing in high resolution on a book.
I have a few tips on photography on my website - it needs some update since it was made several years ago, but gives some ideas for the novice.
2/23 Carlo Maccà added:
"I presume your results could be improved by using a (table) tripod and a separate flash, if supported by the camera. The built-in flash hardly gives acceptable results at the distance required for photographing micro shells."
2/23 Jim Miller added more ideas:
"The key to getting the very best shell shots is a good flash system. Most onboard flashes produce acceptable results, but I've found that a separate flash unit, fired as a "bounce" off a piece of cardboard produces the best results. There are also flashes that accept "soft boxes," which are diffusers that spread the light out more evenly, thus reducing harsh shadows. Why don't you send me a couple of photos and I should be able to tell you what you can do to improve them. Are you using a manual f-stop? Most digitals tend to use larger f-stops (like f2.4 for instance) in everyday use. I shoot all my shells using a manual f-stop of around f6.5-7.3. Keep in mind that f-stops on digitals are roughly half of a standard 35mm, so f8 in 35mm terms would be around f4 or so on most digitals. This varies according to the size of the internal sensor, but you can use it as a rough formula for conversions. Also, while tripods are critical for tiny shells, I rarely use one for larger specimens (anything over, say, one inch)."
2/23 Martin H. Eastburn added an important reminder about using the macro function:
"I was an AFRS camera man when young. We bounced flashes off a white umbrella. Noting super fancy just a white inside without much writing...
The F stop increases the dept of field in any camera. Larger number means depth is deeper.
If you camera has a macro or micro (depends on vendor) mode (often illustrated by a flower picture) - that is best - it puts the lens into a macro mode and focuses to a shorter distance and often native larger f-stop."
2/24 Andrew Grebneff suggested:
"I would suggest a digital camera with a true macro lens, though, as new scanners won't do the job. An SLR will give better results in theory; small point-&-shoots images suffer from very noticable wide-angle distorsion when used close-up.
The best macro results cane come from an SLR with a 50mm SLR lens attached backward to the end of the camera's own lens; adaptors are available for the major brands, or can be made-up by a machineshop.
Remember to use a tripod or macro mount (modified enlarger stands are ideal) and use the highest f-stop possible to maximize depth-of-focus (this will make for long exposures, necessitating a stable stand to avoid camera-shake)."
2/24 Bob Dayle concurred:
"Another important strategy to reduce distortion is to use a telephoto lens on a bellows (or extention tubes) to get as far away from the shell as possible. Or, use close-up lenses on telephoto lenses (or zoom lenses) to the same end. These 'tricks' cost you in terms of less light getting to the film/CCD.
By all means, heed Andrews's advice here... AND use the delay shutter timer so that the camera has time to quiet down after your hand leaves it. In this sense, CCD-digital cameras rock!... no moving parts to shake the camera.
A full-control digital camera is, perhaps, the prime tool for this job. They don't come cheap, though."
2/24 Andrew Grebneff added:
"Excess unfocused light is what causes the depth-of-focus problem. The light scatters, making the image fuzzy. Cutting down the light by turning up the f-stops cuts out that unfocused light and thereby reduces scatter, giving sharper images.
Digital cameras (and automatic film cameras, of course) automatically increase the exposure time to make up for the narrow shutter opening. This is why a stand is needed... the shutter may be open for as long as a second, and ANY movement will blur the image. Don't move your feet while the shot is going on, as the floor may flex and move the camera relative to the subject.
AND use the delay shutter timer so that the camera has time to quiet down after your hand leaves it.
Of course! No point using a stand if you push the shutter button manually.
In this sense, CCD-digital cameras rock!... no moving parts to shake the camera.
Digital SLRs do... they have a mechanical shutter & flip-up mirror just like film SLRs."
3/3 Paolo G. Albano provided more insight:
"Maybe I am a little bit late, anyway:
- I would not advise to use the highest f-stop, but to use the f-stop at which the lens has the best resolution. This generally happens around f/8, but any lens has its behaviour. To see tests with lens resolution you may visit sites like: http://www.photozone.de/ see for example the Canon 100 mm macro which gave me a lot of satisfaction: http://www.photozone.de/canon-eos/167-cano...-review?start=1
As you can see from istograms, the lens resolution decreases a lot at high f-stop because of light diffraction. I have seen this being particularly evident when using my camera mounted on a microscope which had f regulation, but also with standard lenses there is a visible effect, try it taking pictures of the same subject with the same lens at the same light conditions but with different f. The slight decrease in depth-of-focus can be overcome with softwares like CombineZ while low resolution can't be overcome.
- I would also advise to use remote shutter (both cable or infrared) whenever available from the manufacturer. This saves a lot of time if you shoot many (hundreds) photos as I do."
I found this discussion very useful in photographing my shells of various sizes. I now always use the close up setting on the digital camera and a high f-stop.
One thing I found useful, but not discussed elsewhere, was the value of choosing a suitable background. If you try to photograph a shell against a black background then the exposure of the shell may be ok but the label will be washed out. Likewise if you photograph against a white background, the label will be fine but the shell will be dark.
To overcome these exposure problems, I found by experimentation that photographing aganst a pale blue or pale green matt background gave an excellent exposure for both the label and the shell.