All excellent questions, Pete. Here are some answers.
The ubiquitous 35mm silver halide film actually measures 24mm by 36mm. This
translates to a 1:1.5 ratio. The print size of 4X6 is actually the only
standard print size that allows for the whole negative to be on picture.
Sizes such as 5X7, 8X10, 11X13 and 13X19 approximate, with various degrees
of closeness, the 1:1.5 ratio. If you go to poster size, you can get a
24X36 inch poster that will show the whole picture also.
Digital photography perhaps owes more to TV than to film, at least in its
infancy. As such, the CCD has a 1:1.333 ratio. Incidentally, this is also
the ration of computer monitors. Same ancestry. Therefore, when you look
at the VGA standard (640X480) you see immediately that you have a 1:1.333
ratio. The SVGA and higher pixel count standards are made up by multiplying
the VGA standard by some factor:
VGA: 640x480.
SVGA: 800x600 (VGA * 1.25)
XGA: 1024x768 (VGA * 1.6)
1280x960 (VGA * 2)
UXGA: 1600x1200 (VGA * 2.5)
The above dimensions are all 1:1.333333.
Now, you take the standard 35mm negative and the resulting standard print
sizes:
24mmx36mm: 1:1.5
3.5x5: 1:1.4857
4x6 1:1.5
5x7 1:1.4
8x10 1:1.25
11x14 1:1.2727
13x19 1:1.46158
24X36 1:1.5
You immediately notice 2 things. 1) Only 4X6 and 24X36 give you the "whole
picture." 2) All the other "standard" sizes fore the original image to be
cropped in some way.
There is also a third thing you should notice, the 8X10 and 11X14, two
popular size, have ratios less than the CCD in your camera. In other words,
in order to print at these sizes, you will have to trim pixels from the long
side. The other sizes would have pixels trimmed from the short side.
Now, on to some printing issues. In order to print nice pictures, you have
to have the DPI count at around 300 or above. Much less than this and the
pictures will definitely by digital in nature.
I developed a table to help me out with the calculations at various sizes of
print output. Your camera is a 1.9 MP model, since you have given the size
as 1600x1200. This means that at the 4x6 size, your DPI will be 266.667.
This is sufficient to print a very nice picture without doing anything to
increase the pixel count. If you wanted to print a 5x7 picture, the DPI
would be 228.57 still ok, but the picture will definitely betray its
digital, rather than silver halide, origin. An 8x10 would of course have a
DPI of 150 (beware the main dimension here is the short one.) The resulting
print will suck, big time.
In order to print a 4X6 picture, you will need to crop to the dimension you
listed. For a 5x7, the cropping dimension would be 1600x1143, i.e., drop 57
pixels from the short dimension. Other sizes are out of bounds.
My current camera is a 3.34 MP model (2048*1536 (3.2* VGA or 2 times XGA).
The native DPI at 4x6 is 341.33; at 5x7 it is 292.57; and at 8x10 it is 192.
When I want to print a nice 8x10, I use Genuine Fractals, a PhotoShop plugin
to increase the pixel count to 300. The results are excellent.
If your preferred size of output is 8X10,
The 4MP have a CCD size of 2272x1704 (VGA *3.55) and at a size of 8X10,
the DPI would be 213, still quite a bit short of the desired 300.
The 5MP have a CCD size of 2560x1920 (VGA * 4) and at a size of 8X10, the
native DPI would be 240. This is starting to look good.
In order to have a good DPI of 300 for the short side of an 8X10, we need a
dimension of 2400*3200 or 5 times VGA. This represents a 7.7 MP camera. At
the current rate of development, I would expect this camera sometime in
2003. At that size, the 8x10 prints will be better than regular 35mm silver
halide. I do not think that camera will increase the size of the CCD
forever, I think 8 or perhaps 10MP should be then top end. Just like
laptops have raced to the largest possible LCD panel, the largest size,
about 15.7 was reached 2 years ago and has not been surpassed since. On the
other hand, flat panels are increasing in size, but remain at the desktop.
I hope I have answered your questions.
One last thing, there is nothing preventing you from printing whatever size
or dimension you want on an 8.5x11 sheet. I have done that many times and
will continue to do so. I have printed 5x8 or 5x5, or 6x5 or whatever the
results of a judicious crop operation left me with. This is not an issue,
be bold and have fun.
Kind regards,
Denys. . .
Denys Beauchemin
HICOMP
(800) 323-8863 (281) 288-7438 Fax: (281) 288-7438
denys at hicomp.com www.hicomp.com
-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]]On Behalf Of
Pete Osborne
Sent: Saturday, January 12, 2002 3:00 PM
To: [log in to unmask]
Subject: OT: Digital Photography
Hello All,
After discussion on this topic a few weeks back, I decided to post this
here.
I recently bought an HP Deskjet 940C to compliment my Canon Powershot S100
to start printing some of my digital pictures on fancy paper. I've purchased
some commercial printing drivers and have the USB connection working with
Linux. Now I'm ready to print but I am very confused by a few things.
HP and other companies seem to be pushing 4x6 inch printing. Printers that
print only this dimension as well as paper pre-cut to this domension are
available. What I find confusing is that digital cameras take pictures at
1600x1200 or some other resultion with the same 4x3 ratio. Now, if I wanted
to print one of these images 6 inches wide, the height would be 4.5 inches.
What's up with all this 4x6 stuff?
I could crop my photos to 1600x1067 to aquire this magic 6x4 ratio but then
I'm loosing some of my image. Is the reson behind this dimension purely
because of non-digital photography?
Thanks,
-Pete
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