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Old Dec 11, 2006, 11:10 AM   #11
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Dear dermatologist,

If you need to take close-up pictures of wrinkles and creases, you may need a lens with some macro capability (well, not extreme close-up and life-size magnification). When coupled with a ring flash, the problem with shadow casting can be minimized.

Read this short introduction article about ring flash and macro photography:

http://www.adorama.com/catalog.tpl?o...article=041904

(More articles on macro photography (for "true" macro (1:1 life size) photography which may not apply in your case, but still good read:

http://www.adorama.com/catalog.tpl?op=academy
[GO MACRO] button)

You must remember, the quoted focal length ("mm") of the lens are all referred to 35 mm cameras: you need to make a conversion for digital camera lens (eg. Pentax K100D has a crop factor of 1.5, which means a 18 mm lens has a 18 X 1.5 = 27 mm focal length equivalence on a 35 mm camera).

If you are interested in the Pentax K100D, the 18-55 mm kit zoom lens has a quoted magnification factor of about 1:3 (which means it will show 1/3 of life size in close-up mode - or, if the life size object is 1 inch across, it will show that as 1/3 inch in the picture). I guess you really want to show a wider field of a group of wrinkles and not extreme close-ups of one wrinkle (at least this is what I presume from looking at cosmetics ads!), so this macro range is probably good enough as a starter. The other Pentax kit lens, the telephoto 50-200 mm lens, has a smaller magnification factor 1:4. If you need more close-up, you can buy lens with true macro capibility, but that is another story.

Ring flashes, just like ordinary external flashes, come with different power ratings and ranges. Depending on the distance from the object you are working with, you may not need an ultra poweful ring flash.

I think the best thing is to go to a photo equipment store, ask them for the K100D with the kit lens (or any other lens you want to try), and ask them to put a ring flash on and test it out on the sales person's wrinkles - this is the beauty of digital photography where they can download the picture onto the computer in the store and let you see the result immediately.

Remember: you probably have to fiddle with the camera settings (aperture, shutter speed etc.) quite a bit to get the perfect picture, because I think lighting accuracy is more critical for ring flash photography due to the short range of the illumination. Also remember you may also want to adjust the white balance to correct for/enhance the skin tone, which may also be affected by the flash lighting.

Unfortunately I don't do and in fact know little about hands-on macro photography and ring flashes, but I am aware of these and I think this may help to solve your problem and get good quality pictures for your business.
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Old Dec 11, 2006, 11:30 AM   #12
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dermatologist-

Question: A-1. At this point in our discussion, I think it would be helpful to define some of the parameters, more precisely. IMHO, a portrait type photo is taken so that it produces an image of the person roughly from the waist to the top of their head, with space around the head and shoulders. This type of photo is normally taken at a distance of 3 feet to 6 feet from the person. The ideal focal length to take this type of image would be (in 35mm terms) a 80 to 110mm lens.

Question A-2. A close-up photo is a photo that is taken from a distanceof any where from 30" to 3" from a person's facial surface.

Dermatologist: Are these two photo types, the two categories of photos that you desire, and we are indeed discussing? Or is there a need to modify the distances so we can be more definitive regarding the lenses required?

The Pentax 18-55mm kit lensfound on the Pentax K100D camera,is a digital lens designed for the smaller APS-C imager used in the Pentax K100D camera. Therefore the traditional 1.5 multiplier need not be applied. This particular lens will do close-up's as close (approximately) 2.5 to 3 inches, full face photos where the hair is pulled back and just the person's face is visible, photos of the person's head and shoulder's tightly cropped, and "semi portrait photos" of a person's head, shoulders, and down to mid level on a person's chest, with ease. Personally, I believe that will be sufficient for the dermatologist's usage, at least initially. as I own a Pentax K100D with the kit lens myself, I feel sure that the described photos can be taken with ease. I am beginning to doubt that a separate additional lens will be required or that a portrait type photo will be required.

Dermatologist: Please confirm or ammend that the photos, that you desire, andthat we have discussed, thus far, can be accommodated by the Pentax 18-55mm kit lens?

IMHO I would not use a multiplier lens attachment at all. I do not feel that it will be required. After some reflection, I believe that most of the photos that you desire can be accommodated by the kit lens. Try the kit lens and see if you get the photos desired. If you do not, then and only then would I add a second lens.

Ibuy my equipment online from internet merchants (like www.buydig.com)that I know, and have dealt with in the past. However, I live in a small town where there is a distinct lack of appropiately stocked photographic stores. The advatage of dealing with a local photographic dealer would be that you could probably work out an agreement that you could do a test with the K100D camera body and the kit lens. If that camera and lens combination worked well, after a test period of 10 working days, the purchase would be final. However, if dermatologist determined during that 10 working day test periodthat an additional lens or lenses were needed, then dermatologist would have the option to purchase just the camera body alone and the needed separate lenses.

The Pentax dedicated flashes are in my opinion, overpriced. A less expensive flash such as the Sigma model EF-500 DG-ST with the Pentax PA-PTT module which fully tilts (see the photos in my next post, please) would most probably work well, when one considers the distance from which the photos will be taken.Because on camera flash lighting is very flat, it most probably will not show the skin detail that you desire. I would suggest that you save several hundreds of dollars and begin with the Sigma flash, using it in the full upward tilt position so that the light produced will be approximately equal to that of normal room lighting. I will also attach a photo in a subsequent post to illustrate a photo taken using that particular strategy.

Whether you purchase locally or online, the warranties will be exactly the same.

So when my husband returns, we will set up the necessary sample photos to show you exactly and precisely what the Pentax K100D equipped with the kit lens can do, using actual photo samples that you can view on this forum.

MT/Sarah




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Old Dec 11, 2006, 11:57 AM   #13
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dermatologist-

OK, here are the first two photos.

The first photo shows the Sigma flash I posted about previously in its normal position.



The second photo shows that same flash in the full vertical tilt position, such as you would use to bounce the flash's output off the ceiling.



MT/Sarah
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Old Dec 11, 2006, 1:07 PM   #14
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1 & 3 - Portrait lens focal lengths along with a lot of other stuff in digital photography is given in 35mm equivalent. To get the 35mm equivalent focal length of a DSLR lens you have to use a multiplier. A multiplier is not a piece of equipment but a relation of the lens to the size of the sensor. In the case of the K100D with the kit lens that multiplier is 1.5, so your equivalent 35mm focal length is 27 - 82.5mm. That is perfectly fine for your purposes.

I would just get the camera with the kit lens and see how it works out. My guess is that it will be fine for any kind of flash. If you then want to upgrade lenses you will be able to relate the focal length you already have to what you might need.

4 – You get a small amount of quality improvement and a big light gathering improvement with a prime lens. You don't need either for your purposes if you are going to use flash. Quality will be fine from a decent zoom lens and at the ranges you will be shooting you will have plenty of aperture for flash – f5.6 I think with the kit lens at full zoom.

If you are going to carry the camera from room to room you would do best with an external flash. Some are quite tall and would probably work fine from the hot shoe. I think a bracket would work a little better and they aren't pricey. I'm not familiar with the camera but I'm assuming it has a sync connector. If it doesn't you can get an adapter to run the cord from the hot shoe to the flash.

You usually get better prices online. The advantage of a local store is that you can return stuff if it doesn't work out. Warranty is the same, but if you buy an extended warranty some camera stores might handle the warranty service – not common but possible.

The kit lens is a medium wide angle to a long normal. Decide on a camera and then discuss vacation lenses. The kit lens will do fine in the meantime.



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Old Dec 11, 2006, 1:54 PM   #15
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The kit lens will probably be fine for most of your needs - a doctor's exam room isn't really big so you can't get far enough away from your subject to use some of the longer portrait lenses. I could see that you might want some type of macro lens (close focusing) might be useful also. In general, a prime lens is sharper than a zoom lens, so it might make sense to get something like a 100mm macro lens for your individual wrinkle pictures - it would be long enough that you can step back a bit and still get just a small section of eye(several different lens makers have versions of this type of lens).

I wouldn't think that a ring light would do what you reallyneed it to do. Ring lights are great for getting close to bugs/small objectsso the lens itselfdoesn't cast a shadow, and dentists use them all the time because they get good, evenlighting on the whole mouth, but they would fill up your wrinkles. I'd think the Sigma (or similar) flash with the light bouncing from the ceiling would be better.

For your vacations I might suggest also getting the Pentax DA 50-200 lens. It's reasonably good quality, light and not that expensive, a good addition to the kit lens.
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Old Dec 11, 2006, 3:09 PM   #16
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Dermatologist-

Here are the three K100D photos done with the kit lens and the Sigma flash in the full vertical tilt mode (ceiling bounce) position using Auto WB, Auto ISO, and the P for Program Mode on the K100D camera. We made the assumption that you wanted to take the photos as simply as possible. These three photos show what we think are the photos that you desire.

Photo #1 Eye Detail



Photo #2 Face-head to chin



Photo #3 Modified Semi Portrait Mode



Dermatologist, these photos are just a guess as to what you really want. Now we need your feedback, please. Thanks!

MT/Sarah
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Old Dec 12, 2006, 12:29 AM   #17
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Dermatologist-

Here is a regular photo of me, rather than one of the clinical Photos.
This was also taken with Pentax K100D.


MT/Sarah

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Old Dec 12, 2006, 10:28 PM   #18
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