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howto compare quality of still camera with digital

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February 16, 2004 9:28:56 AM

I want to buy a good (but cheap:)  camera for fair+ quality pictures but only for 10x15 sizes.
The truth is I'm thinking about buying the canon A60 or A70.
I prefer to buy the A60 because it's just cheaper and has the same features as the A70 except from the 3 mega pixel.
Now for the topic, If I compare the quality of the digital camera to a still one (standrad one, not a pro) which mega pixel is needed for just a standard 10x15 picture which is printed in a store?
February 18, 2004 3:42:33 PM

It is popular for people to attempt to compare the digital with the analog, as if there were grounds for comparison. Digital technology works a little wonder known as perception. Since it is not possible to quantize a potentially infinite value [such as is found in analog medium], digital panders to the human perception instead. The idea is to capture just enough of the analog to fool perception into missing the difference. Basically, what I am saying is that a digital image, of any size, cannot truly compare with a comparable analog/film image.

However, what you need to determine is to what degree you wish to fool the eye. What looks good to you? Your computer screen displays 72ppi, a cheap printer prints at 300dpi, standard office printers pump out 600dpi. Personally, when I produce digital pictures I print them at 1440dpi, which looks rather nice [to me].
So, for a 10x15 picture @ 300dpi you need an image 3000x4500
10x15 @ 600 dpi = 6000x9000
10x15 @ 1440 dpi = 14400x21600

Now, on the flip side, you can use an image editor like Adobe Photoshop to inerpolate the difference. Which is to say that since there isn't a camera out there that shoots at such inordinately high resolutions, the graphic program will predict the difference and "fill in the blanks" so to speak.

The more you know, the more you know that you know less than you thought you knew when you knew less than you now know<P ID="edit"><FONT SIZE=-1><EM>Edited by TokranePo on 02/18/04 12:43 PM.</EM></FONT></P>
February 19, 2004 2:15:29 PM

ok, thanks, now i'm more understanding.
but a few more things plz:
Correct me if I'm wrong. But when i'm getting a picture with regular film camera, the film itself is in a small size from a 10x15, so I'm guessing somwhere where printing the photo there is an interpolating too.
we can't stretch the printed photo forever :) 
correct?
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February 19, 2004 2:50:57 PM

The primary factor that may limit the size to which film can be enlarged is grain (silver halide grain in the film, itself). And the higher speed a film, the larger the grains will tend to be, which limits enlargement possibilities. It's a similar concept to the enlargement limitations with digital, but not quite the same.

<font color=blue>War</font color=blue> <font color=orange>Eagle</font color=orange>
February 21, 2004 4:03:52 PM

NuKe,

"10x15 print": are we talking inches? If so, that's a large print, even for normal film formats like 35mm.

Just looking for clarification.

BW
February 23, 2004 3:20:05 AM

I think he's talking about a 4x6" print. In that case, the A60 will be suffice for most ordinary applications.
February 24, 2004 2:42:12 AM

Thanks,

That makes more sense (10cmx15cm). Someday maybe we'll go metric in our backward country, and I won't have to think so hard...

I agree that the 2MP camera will do for this.

BW
!