My personnal justification for digital cameras:
digital camera - cost $300.
35mm - already purchased - cost $0
cost of film - CVS $8.00 for 96 exposures - about 9 cents per photo.
develpment cost - CVS - $8.00 for 24 photos - 1 hour (about same for 4 day and dual prints). - about $0.35 per photo.
one photo is $0.44
Cost of scanner to digitize photos - $0 - already own.
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justification:
(digital camera - 35mm camera - scanner) / ( cost per photo) = # photos that cost justify digital camera.
In my case above:
(300-0-0)/(0.44) = 681 photos.
When I first tried to justify a digital, the camera I saw was $800. It worked out to over 1800 photos and I figured I'd wait for the price to drop. At one photo a day every day, it would take about 5 years to pay off the camera based on the film and development savings.
I'll stick with my 35mm. If I had enough many not to worry about justifying, I'd get a digital to go with my 35mm. I admit I'm a technophile.