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Re: thoughts on digital cameras


  • Subject: Re: thoughts on digital cameras
  • From: Geographicus <maps@geographicus.com>
  • Date: Mon, 15 Apr 2002 09:37:58 -0400

I've been working on my photo studio for maps and still don't quite have it
right.  I use two flood lights with full spectrum bulbs - but I'm having a
lot of trouble with consistency and white balance.  If there is any other
light in the room - which in this case in unavoidable because of enormous
windows nothing looks quite right.  The best photos happen on sunny days,
but I can't seem to duplicate the effect with my own lighting.  What are
photo floods? Are they in some way different from the flood lights I can buy
at the hardware store?  What sort of bulbs do they use?

Kevin Brown
Geographicus




On 4/3/02 3:31 PM, "Ed Lefkowicz" <seabooks@saltbooks.com> wrote:

> In response to the questions about digital cameras, and issue of
> photographic maps in general, I can offer this somewhat lengthy
> primer.
> 
> Reviews of digital cameras are available from several sources, the
> best link to these being
> 
> http://www.all-digital-links.com/
> 
> I haven't checked all the links given there, but the one at
> dpreview.com strikes me as being incredibly thorough. I checked the
> review for the Olympus 3040, and down on page 14 (!) of the review I
> saw very specific information on lens barrel and pincushion
> distortion. (More on this below.)  So I'd be very inclined to check
> this link for any camera I was tempted to buy.
> 
> Reviews such as those in Consumer Reports are useful to an extent,
> but are intended for most users, not for those of us intending to
> take detailed pictures of flat objects for reproduction.  Which
> brings us to the question of what characteristics should we look for
> in a digital camera?
> 
> The answer, as usual, is "It all depends".
> 
> Digital cameras and scanners break images into pixels, the smallest
> discrete unit of color and density. The greater the number of pixels
> per inch, the higher the image quality. In print terms, newspaper
> photos are screened at something like 70 dots per inch; fine color
> printing can go to 300 dpi, but 150 dpi or so is more common. Look at
> a newspaper photo, then at the image from a good quality art book,
> and you'll see the difference. The smaller the dots, the more the
> image appears continuous.
> 
> If you're reproducing images for the web, 72 pixels per inch is what
> you?re looking for, and if you want to fill the screen, and image
> 1024 pixels wide or so is about as wide as the average screen will
> reproduce in one view, so a camera that will take a picture 1024
> pixels wide will fill the screen.  But (and isn?t there always a
> but?) that leaves no allowance for the fact that we will seldom take
> a picture which doesn't need some cropping, and if you crop off a
> couple of hundred pixels in width, you're down a bit. On the other
> hand, large images take a long time to load, and you probably won't
> want to fill the entire screen with an image, so 1024 pixels wide
> will do it for the web, and nearly any camera will do that these
> days.
> 
> For print, it's a bit more complicated. I read somewhere recently
> (sorry I can't recall where) that you should supply your printer with
> a digital image at twice the resolution to be printed in. If you're
> printing 150 dpi, you'll want an image at 300 pixels per inch. Let's
> say you're doing, as I do, a catalog cover 11 inches high. At 300
> pixels per inch, that's 3,300 pixels wide, or somewhere around an 8
> megapixel camera. Forget it! Scans, if you can do them, are far
> easier.
> 
> But if you?re producing a catalog 8.5 X 11, with margins, you could
> get a 7-inch wide image across a page, or 2,100 pixels wide. A 3
> megapixel camera would do that. (2,100 pixels wide by, say 1,500 high
> = 3,150,000 pixels.) And if you were to supply your printer a 150
> pixel per inch image, a 1 megapixel camera would do it.
> 
> In terms of other desirable qualities in the camera, look for
> rechargeable batteries (NiMH batteries are pretty good, and available
> in AA sizes, which a lot of cameras take.) Digital cameras eat
> batteries! USB or firewire connections are pretty much ubiquitous,
> and necessary-?big files take a long time to transfer. And large
> swappable memory in whatever configuration is useful, too.
> 
> Look for a lens with as little distortion as possible. It is quite
> possible to make even very wide angle lenses with no observable
> distortion. However, these are very expensive, and, needless to say,
> they don't put them on consumer-grade digital cameras. But check the
> reviews, and stay away from the really bad ones. Look too for a
> camera with, in general, good image quality and little chromatic
> aberration. Dpreview.com has good information here.
> 
> Look, too, for a camera which will allow you to either make manual
> exposure settings or at least to make exposure compensation.
> 
> My guess is that the biggest reason for lousy pictures of flat
> objects is a result of poor lighting. In general, you should not try
> to use the camera's built-in flash, for two reasons. First, the flash
> will overilluminate the center of the object you?re photographing, so
> that will look washed out, and the edges will be dim. Second, if the
> surface of the object is reflective at all, it will be even
> worse?ever take a flash picture square on in front of a window?
> Bright, isn't it?
> 
> The alternatives are soft (indirect) natural light or light sources
> at angle to the object, illuminating it from all sides. Four simple
> photofloods in cheap reflectors should do it. (You can try regular
> incandescent bulbs, but the color temperature of the light is
> different, and you photos may look too orange. This can be corrected
> in PhotoShop, but it's a lot easier to get it right the first time.)
> Put the lights beyond the left and right edge of the object, at a 45
> deg. angle or less, and you'll probably be OK, even if the object is
> framed under glass. In that case, though, try to kill all extraneous
> light, and maybe even tent yourself and camera with a big, black
> cloth, so you don't get a mirror image of yourself in the picture. Be
> certain to shut off the camera' s built-in flash, and change the
> camera's color balance to tungsten.
> 
> I hope this helps. I've been taking pictures seriously for over 35
> years, and have taught basic photography. (If you're truly interested
> I'll send you the link to my photo web site, which is reflective of
> what I do when I'm not selling rare books, manuscripts and maps.)
> 
> Almost forgot, because someone is sure to ask. I use a Kodak DC260,
> which works just fine for my purposes. It's a couple of years old at
> least. 
> 
> I hope this helps!
> 
> 
> 
> 
> Ed Lefkowicz
> Edward J. Lefkowicz, Inc.
> 
> Rare and unusual books, manuscripts and maps:
> Especially voyages by sea, nautical and naval subjects
> 
> 500 Angell St.
> Providence  RI  02906  USA
> 
> Voice:     401 277 0787
> Toll-free: 800 201 7901 (U.S. and Canada)
> Fax:       401 277 1459
> 
> Visit our Web site at www.saltbooks.com
> 
> 
> 
> This mailing list is brought to you courtesy of:
> Barry Lawrence Ruderman
> Old Historic Maps & Prints
> http://www.raremaps.com/
> 

This mailing list is brought to you courtesy of:
Barry Lawrence Ruderman
Old Historic Maps & Prints
http://www.raremaps.com/


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