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Old Mar 20, 2004, 7:18 AM   #1
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Default Tough question about zoom and pixels

Is it better to have more optical zoom, or more pixels for distant shots?

Lets say I have a 3MP digicam with a 4X zoom and I frame a shot at full zoom and snap a photo. Now, lets say I take the SAME shot with a 4MP digicam with only 3X zoom and I zoom it so that the previously framed shot ocupies the SAME NUMBER OF PIXELS (after cropping). The result is that I have 2 photos that are 3MP - one zoomed and the other cropped. All else being equal, will the resulting images be the same?

Tough to explain - hope you get the point of my question.

Jim H.
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Old Mar 20, 2004, 8:05 AM   #2
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That is an interesting question! I understand but I dont know the answer!

If the sensors in both cameras are of equal standard.....then perhaps the shots will be nearly identical.

But this is an uneducated view! So maybe someone else can help more!
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Old Mar 20, 2004, 8:57 AM   #3
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Distant shots need more optical zoom. Bigger prints need more pixels.
For example is like saying: why should one get, eg. the fuji S5000 (10x, 3mp) and not get one of the new compacts with 6mp and 3x optical zoom? (if both produced the same result, one by zooming the other by croping?)
The S5000 will let you get closer with the 10x optical while the 6mp one will allow bigger printouts but the magnification of a specific photo will be 3x not 10x.
This is how i understand it at least..,

hope this helps
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Old Mar 20, 2004, 9:26 AM   #4
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Quote:
Originally Posted by jhimmel
Is it better to have more optical zoom, or more pixels for distant shots?

Lets say I have a 3MP digicam with a 4X zoom and I frame a shot at full zoom and snap a photo. Now, lets say I take the SAME shot with a 4MP digicam with only 3X zoom and I zoom it so that the previously framed shot ocupies the SAME NUMBER OF PIXELS (after cropping). The result is that I have 2 photos that are 3MP - one zoomed and the other cropped. All else being equal, will the resulting images be the same?
The short answer is yes. However, you can't crop as much as you think you can, and end up with images that have the same number of pixels.

So, in your example above, you would not be able to shoot at full zoom with both cameras, and crop the 4MP image to have the same number of pixels (if the focal length of the lens on the 4MP cameras was only about 25% greater on the long end).

Bear in mind that if you crop an image to look like twice the optical zoom was used, you end up with an image that is only about 1/4 the original resolution (because resolution is computed by width x height). Another way to look at it, is that it takes 4 times the resolution to double the image size.

digital_ray_of_light has been updating a table on his web site to show resolving power of popular digital cameras, based on a formula described by Rodger Carter and Rick Matthews (Telephoto Figure of Merit: Explanation and Uses).

You can find it here (along with links to the formula explanations):

http://www.geocities.com/digital_ray...oomzoomv5.html

Note: the interpolated tests results in the table, are not valid measurements of resolving power (use the 3 Megapixel, non-interpolated output mode instead), since the newer Fuji Models do not appear to have any increased detail shooting in 6MP output mode.

So, the current Optical Zoom "king" (straight from the box) is the Panasonic DMC-FZ10.
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