Choosing between two Canon Macro lenses

I would definitely NOT select the 50mm f/2.5 Macro because this lens cannot achieve 1:1 image ratio (The image on the sensor being the same size as the subject) without the use of an accessory adapter.

As per the Canon wed site:
"A superior-performance lens offering excellent optics and focusing from infinity down to one-half life size (0.5x). Its nine-element design features a floating optical system, which ensures top-notch performance even at close focusing distances. Light and compact, it functions beautifully as a general-purpose normal lens. The optional accessory Life Size Converter EF enables focusing down to life size (1:1), and actually increases working distance - very desireable in close-up shooting."

The problem with this type of setup is that if you want to shoot anything between 1:2 image ratio (wherein the image is 1/2 the size of the subject) and 1:1 (explained above) you must add the adapter. That means setting up your shot all over again which would be a PITA for your patients. That also means if you want to cover an area smaller than 44.4mm x 29.6 mm you have to add the converter and then if you want to cover an area larger than that, you have to take off the converter. The 100mm Canon (and most other true macro lenses) will allow stepless focusing from infinity down to 1:1.

Also lenses below the 100mm focal length will require you to get your lens and flash in too close to the subject's mouth.

I am certainly no expert on what is needed in a dental image. My dentist never used a tripod. He also did not use a ringlight because he said that shadowless imaging did not show him what he wanted to see. Instead, he used a pair of small flashes on a dual rig. Ring flash is easier to master while twin flashes may give slightly better results. See the section on flash in this web site...

http://www.edmclaren.com/Pubs/PDFs/t...en_article.pdf

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Originally Posted by rpcrowe

He also did not use a ringlight because he said that shadowless imaging did not show him what he wanted to see. Instead, he used a pair of small flashes on a dual rig. Ring flash is easier to master while twin flashes may give slightly better results.

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I do agree with you that the ring lite has its problems - the ring lite is what my local photo shop has sold to a number of local dentists.

I'd first try the dentist's task light system which can be angled or positioned in a variety of ways for better light modeling.

Glenn

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Originally Posted by Hero

In this case I wonder if extra distance is really a pro. Usually when shooting through a peephole (the mouth in this case) you want to be able to get as close as possible to have as much angular freedom as possible. ie you don't want to have to walk around the patient to find the angle you need. Besides, contrary to shooting insects, you don't have to be afraid of your subject flying off when you get too close.

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What I use everyday is a cheek retractor - it extends the lips to the sides so much that you actually see NO lips in the image. So a peephole actually turns into a WORLD. Y'all dont even know the ability of your lips to extend. When I first put a retractor in a patient's mouth 5 years ago I said WOW.

Furthermore, pics of back teeth are actually reflections in a large mouth-mirror. Using mirrors definitely enlarges the peephole.

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Originally Posted by Glenn NK

Mike:

That would be a very good solution. It also provides a place to put the camera when it's not needed (most of the time).

It wouldn't encroach on the patient's "space" as much as hand-holding. However there could be a considerable price for the adjustable mounting system.

Glenn

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Funny to read all that talk about "patients' space". Don't forget that us dentists are the same persons who put quite a few fingers into patients mouths almost up to the pharynx, so who cares about standing 4 inches close to them 30 minutes after that???)))

Overall, thanks to everybody for your indepth replies, Glenn especially, I'm so much thankful to everyone that I could never pay you back. Thanks for encouraging in photography as well. I'm buying the 100mm Macro and as soon as it arrives and I have some practice, we'll see what happens.

Doctor Andrei:

Thanks for the kind words.

I don't know why we were worried about the "patient's space" - of course you are right. Many years ago, I considered going into dentistry but I realized that I wouldn't be able to be so close to patients as you guys get, so I opted for structural engineering (at least I got to build bridges ;)). I had my teeth cleaned and a bridge done recently, and I know that a camera in my face would have been a nice break from all the fingers.

Best wishes with your personal and professional photography.

Glenn