Ideal Macro lens for my dental work

Discussion in 'Canon EOS' started by rod_cart, Mar 25, 2006.

  1. Dear Guys: I�m a macro shooter ,also i�m a dentist; after think about a few months i got a simple hard question: I Must take all pictures with this equipment: 1- Canon eos 300D digital body 2- Macro Ring Lite Canon MR 14 ex (ETTL) 3- Macro lens (actually i�m using a Vivitar 3,5 macro lens 100 mm) The diafragm MUST BE Stopped Down to F22 or F32 (In order to maximize the shallow depht of field),and 1/125 in obturation speed (in order to achieve a good anti shake result) The focal distance is about 24 cm from subject (patients mouth) I�M considering to buy a new better macro lens , after my personal review , im thinking in 2 options: 1- Canon 50mm 2,5 Compact macro 2- Canon 100mm 2,8 USM Macro 3- Tamron 90mm 2,8 Macro Di 4- Sigma 105 mm Macro EX DG I need to know which of this lenses is the best performer in this especifical situation because all the MTF charts i saw only consider the lenses stopped down to f8 , then i got no information in this stopped down , ring lite situation The problem is i dont want waste money buying a expensive macro lens (like the canon 2,8 100 mm , if the final results for my especifical job are equal or even better with a cheaper lens, In fact i saw excelent MTF charts and rankings for the canon 50mm compact macro but I dont known if this lens is the best in this situation) I Need obviously the more accurate colors and sharpness in the photo, but i need your help
    00Fmzn-29046484.jpg
     
  2. A couple thoughts....

    Working distance is determined by focal length. If you want to shoot closer to the patient, then buy the 50mm lens. If you're comfortable with the distance you currently have, then a 100mm or so lens would be the way to go.

    Personally, I'd spend the extra money for the Canon 100mm f/2.8. It will probably hold its value better in the long run. The Tamron 90mm is also very well regarded. You probably wouldn't notice a difference in image quality between it and the Canon. The main differences would be autofocus speed, noise, and build.

    If you really need to shoot at f/22 - 32 to get the appropriate depth of field, then all these lenses will perform similarly. Once you go beyond about f/16, final image quality is limited by diffraction. Using f/32 will increase depth of field, but at the expense of overall resolution.
     
  3. I've encountered a couple of dentists in recent months, both have used specialist dental video cameras and displayed the results on a TV.

    If you charge at the same level at which I have been charged, why try to get away with doing things on the cheep. And from a patient point of view, I would not be very pleased if my dentist was stinting in any way on my treatment.

    Just my thoughts.
     
  4. What do you not like about your current Vivitar set up. At f22/f32 the Vivitar should not do much worst then the lens you listed above.
     
  5. At f/22 you will not see any improvement with a more expensive lens. Color saturation and contrast can be set with the parameter section in the camera's menu. What the Canon 100mm will do is offer faster auto focusing, but that's often not used in macro, so it may not help you. The Canon 100mm will also get you to 1:1 macro without adding an adapter. Both the Canon 50mm f/2.5 an the Vivitar require adapters (different types) to get to their closest focusing.

    The 100mm f/3.5 Vivitar is actually quite good optically even with it's 1:1 adapter. Focuses very slow though, and feels like a piece of junk.
     
  6. Peter,

    Outside of the US the medical professions are much less of a profit making enterprise. It is not even unkown to have a doctors office that has more medical professionals than accountants ! I don't think taking pictures of your teeth using a "lesser" lens counts as stinting on treatment.

    Rod,

    Hello again. Thank you for posting a sample. The magnification there is quite low - less than the 1:2 that the compact macro is capable of without the life-size adaptor. How big do you wish to make the image ? If you only wish to get images that are small you can move the camera back, drop the aperture to f16, and crop the image. This will give you more depth of field. The resolution of TV and journal images is very low.

    For instance using a 90mm on your Canon 300D with a subject distance of 60 cm lets you capture 10 cm x 17 cm with a depth of field of 2 cm at f16.
     
  7. Besides, what gives better stills-- a tv camera or a dslr?
     
  8. The optical performance is pretty clear now for me;
    thanks for answering me (especially to Alistair Windsor), i got now another doubt:

    For macro 1:2 ratio and 1:1 macro ratio wich lens give me more depht of field at same settings?

    1- Canon 50 mm 2,5 compact macro (1:1 considering the ataching of canon life size converter i already got)
    2- Canon 100 mm 2,8 Macro
     
  9. The wider lens will always give you more depth of field at the same aperture.
     
  10. I had a Vivitar like yours as my first macro lens, and I agree with the other posters that for what you are trying to do, it should give fine results.

    I'd try using flash-only lighting. Set your camera on manual, set shutter speed to 1/200th second (or whatever the flash synch speed of the Digital Rebel is) and f/16, ISO 200 (you might find that ISO 100 works fine, but I am being cautious) compose your shot, hold it steady, and fire away. You should get fine results. The MR-14EX isn't a terribly powerful flash, so you may have to either crank the ISO slightly or else open your f/stop up a bit, but I suspect it will work fine at the settings I listed.
     
  11. Actually Andr&eacute; at macro distances the DOF is essentially independent of the focal length (though lens design matters). Actually since longer lenses are usually telephoto designs with pupil magnification less than 1, whereas shorter lenses are either retrofocus or symmetrical designs, for very short subject distances often the longer lens will have great DOF than the shorter one. <P>

    Check out http://www.vanwalree.com/optics/dof.html
     
  12. I have read that for practical purposes, at the same magnification (size on film/sensor plane) and same aperture, the DOF is the SAME whatever lens you use. More focal lentgh means more working distance.

    For accurate colors you need to adjust the white balance to flash or use SpectroShade from MHT or Shadepilot from Degudent.

    Regards
     
  13. I take pictures of wounds and I have the 50mm 2.5 macro and a Kenko 2x multiplier to accomodate the different sizes of wounds seen. Flash is an Olympus RF-50 (autoflash) fired by hotshoe adapter. With smaller wounds, there is a significant deal of distortion seen when the lens is so close to the subject. This is apparent as I include a paper tapemeasure in each picture to maintain scale and monitor interval changes properly. For wounds that involve the entire leg and foot, the 50mm is excellent. If I use the 100mm in those situations, the flash may not be adequate.
     
  14. If you need the lens only for this work exclusively, may be MP-E65 lens is your best choice? It goes up to 5x life-size, but you have to focus by moving whole camera forward and backwards (turning the lens only changes magnification). Have a look at samples in Canon Camera Museum
     
  15. Ilia,

    Rod seems to wish to take pictures of patients mouths rather than small parts of individual teeth. This is more like 1:3 magnification (on 1.6x crop factor camera) not 5:1.
     

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