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Old Jun 15, 2002, 4:15 PM   #1
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Default Macro pictures + ring flashes

Yet another depth of field question....

I'm looking to upgrade to the 7i for intraoral dental pictures, basically macro pictures that need lots of light and more importantly lots of depth of field to have all teeth in focus, plus since its a hand held shot it needs to have reasonable shutter speed. If I shoot aperture priority at max F stop (9.5?) what can I expect the macro depth of field to be at the spec'd 2 inch field of view? What kind of shutter speed will I see?

Also is there an advantage to buying the Minolta ring flash as opposed to the Vivitar which is less than 1/2 the cost?
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Old Jun 21, 2002, 2:10 PM   #2
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Ok maybe if I get more specific I'll get a response:

1) Can I still shoot aperture priority in macro mode?

2) How easy is it to manually/auto focus in macro mode, most of the macro pics on the review sites either have very limited depth of field or are out of focus?

3) Can I shoot small aperture priority (F9.5) with a (ring) flash?

Thanks for any info
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Old Jun 21, 2002, 7:22 PM   #3
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Yes you can shoot macro mode with aperture priority - or any exposure mode. The advantage of using the Minolta macro flash will be true TTL control of the flash. Using a flash like the generic Vivitar ringflash means that you have to manually control the exposure for every shot - you'll get much more reliable exposures with TTL control.

As for the depth of field range I am not exactly sure, sorry. The D7i has two macro focal positions, full zoom and full wideangle. Full zoom will have the least focal distortion but also the least DOF. I would imagine that you would use the wideangle setting which will also yield the most DOF.

Let me know the results, I'd like to see some of your intraoral shots and possibly post one of them on the sample photos page as I imagine other dentists would also be interested in the outcome.

I know it's more expensive but probably the best results would be obtained using a Canon D60 or Nikon D100 with the appropriate macro lens and macro flash. The digital SLRs used to be very expensive but with the cost down to around $2K it is much more reasonable now.

-Steve
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Old Jun 22, 2002, 8:01 AM   #4
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DrSmile

While I agree with Steve that an SLR with interchangeable lens has more flexibility in term of macro lenses; However, the challenge you'll face is the limitation of your patient's mouth and you'll be restricted to only frontal shots. It's even more so with the larger and heavier D60 than the 7i. Imagine the reaction of your patient once they saw the huge camera equipped with equally large circular ring light that you try to go down their orifice!

I'm sure that you can find in the dentistitry journals camera companies advertising their wares of endoscopic oral cameras... You can try both the D7i and the D60, it will do the job but the shooting angle along with it's flash very restrictive (more so than the DOF)...
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Old Jun 22, 2002, 9:06 PM   #5
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Thank you very much for the info Steve. I understand the true SLR / interchangable lenses would be ideal quality wise, but the tremendous amount of wear and tear that the camera will see makes me want to consider something with non-interchangable lenses and quite frankly, less valuable in case it "disappears" or more likely gets dropped on the floor...

NHL the intraoral cameras you are speaking of are not suitable for my purposes. I need high resolution pictures of entire arches, not individual teeth. My current antiquated setup of a DC290 is ill suited for this purpose, you can see some examples below. Note the depth of field issues in the frontal picture:

http://mywebpages.comcast.net/njdsm/P0000004.JPG

http://mywebpages.comcast.net/njdsm/P0000007.JPG
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Old Jun 22, 2002, 11:14 PM   #6
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DrSmile

Like they say, a picture is worth a 1000 words... I don't think you can get the DOF in macro with F9.5 @ the minimum focusing distance, but at the regular 200mm setting here's what I got:
http://www.pbase.com/image/2666023/original
Is it enough for orthodontic work? That's more than 3" and only with the built-in flash !!!

[Edited on 6-23-2002 by NHL]
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Old Jun 23, 2002, 11:43 AM   #7
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NHL,

Thank you for the picture. It certainly appears to be adequate for my needs IF I can get a similar DOF at about half the field of view in your picture. Will the objects remain in focus if the object is that much closer? If you could take the same picture with the watch including wristband taking up 90% of the frame side to side that would give me a better idea.

Do you have to manually focus for this pic or can you just point and shoot in aperture priority and get consistent in focus pictures at this distance?

Thanks
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Old Jun 23, 2002, 2:30 PM   #8
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DrSmile

You definitely lose DOF as you get closer and going to the macro mode (.25m - .5m). The EVF indicated .47m distance for this shot:
http://www.pbase.com/image/2677972/original

I recommend to stay @ the long tele (.5m and above) and crop in Photoshop to get the desired DOF results since there's so much croping room with a 5 Mpixels camera. You'll need to re-size the picture anyway why not just cropped them! (BTW the posted pictures are already re-sized more than 1/2, ie 2560x1920 to 1056x792 or 26x35" to 11x14")

[Edited on 6-23-2002 by NHL]
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Old Jun 24, 2002, 12:43 AM   #9
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Thank you for the picture NHL.

I would like to use full resolution pictures where the dental arch fills the entire frame as my current resolution of 1500x1000 is far from adequate and I need to see much more detail. Seeing the DOF problems in your last picture makes me think Steve is quite correct and that I will be better off with a pro SLR.

Thank you for all the help.
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Old Jun 24, 2002, 7:54 AM   #10
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Bear in mind that my D7 is limited to only macro at tele; whereas the D7i has macro at the wide angle as well which offer more DOF than my camera could.

Also unless you go for the Contax which has a full frame CCD, the other two digital SLRs that Steve referred to has a x1.3 - x1.5 factor so that'll push the lenght cost factor a little bit higher as well @ the wide angle which is what you'll need for more DOF...
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