Higher MegaPixel = More Zoom?


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xiaoming

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#1
Say when you took a 6MP picture with your DC. Upon viewing it on your PC, you feel that the subject is small and decided to make it looks bigger by cropping the entire picture to a smaller size (say 2MP).
In this way, the subject will be bigger on a 4R print and the picture still look sharp since 2MP is sufficient for a 4R print.

How different is this method compared to optical zooming?
 

toasty

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#3
Optical zoom means shifting pieces of glass in the lens so that the image generated on the film or CCD is actually a crop of what it would be otherwise. Optical zoom is determined by the lens. Note: lenses cannot resolve arbitrarily small detail.

Digital zoom means just zooming in on the picture and is not a useful feature for a DC to have. It's more of a marketing thing (I think). The effect of optical zoom and digital zoom, is more or less the same though. Having more pixels gives you more or less the same effect as having more optical zoom, because you can resolve more detail in your pictures.

Once however the pixels become closer together than the lens is capable of resolving, adding more pixels will not give you more detail. At that point to get more detail, you need better glass.
 

ST1100

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#4
Sorry Mystix, it's not the same. What xiaoming is describing is digital zooming - essentially, it is cropping.

Optical zooming (in your example) uses the glass to magnify the subject, and the subject in your cropped area (your 2MP) now occupies 6MP - with full 6MP of detail.

The 4R printed from the 2MP and the 6MP may or may not be the same quality - a lot of factors are involved. But all things constant (quality of processing/handling), i think in some cases, you might see a diff in the two, even at 4R.
 

mpenza

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#5
Originally posted by xiaoming
Say when you took a 6MP picture with your DC. Upon viewing it on your PC, you feel that the subject is small and decided to make it looks bigger by cropping the entire picture to a smaller size (say 2MP).
In this way, the subject will be bigger on a 4R print and the picture still look sharp since 2MP is sufficient for a 4R print.

How different is this method compared to optical zooming?
What you're doing is a form of digital zoom. Every 50% reduction in terms of number of pixel is equivalent to a 1.4x increase in zoom.
 

Astin

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#6
Besides of what has been said above, you still need to consider the DOF effect, the perspective effect, the colour fringing, etc.
Bottom line, they can produce similar results but they are not exactly the same.
 

xiaoming

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#7
Many thanks for your enlightenments. They had been very enlightening!

So the general conclusion here is the cropping = DIGITAL zooming

But xiaoming still a bit confused :confused: (sorry, xiaoming's brain a bit slow :(

Cropping = Digital Zoom?
What cropping do is really removing parts of the picture that I don't want. No zooming involved, right?

I think the zooming portion is done when we develop the cropped photo (instead of the original photo) into 4R. This is the where digital zoom is performed, right?

The key question is:
At 4R size, can the "normal" human eyes detect the any quality differences between:
(A) An object zoomed in at 6X optical zoom using a 2MP camera
(B) The same object zoom in at 2X optical zoom using a 6MP camera, and the picture is cropped to 2MP size.

Note: "normal" human eye means: Given 2 photo- (A) and (B), can you immediately tell which photo is (A) and which photo is (B), say within 3 sec?
 

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#8
Originally posted by xiaoming
Many thanks for your enlightenments. They had been very enlightening!

So the general conclusion here is the cropping = DIGITAL zooming

But xiaoming still a bit confused :confused: (sorry, xiaoming's brain a bit slow :(

Cropping = Digital Zoom?
What cropping do is really removing parts of the picture that I don't want. No zooming involved, right?

I think the zooming portion is done when we develop the cropped photo (instead of the original photo) into 4R. This is the where digital zoom is performed, right?

The key question is:
At 4R size, can the "normal" human eyes detect the any quality differences between:
(A) An object zoomed in at 6X optical zoom using a 2MP camera
(B) The same object zoom in at 2X optical zoom using a 6MP camera, and the picture is cropped to 2MP size.

Note: "normal" human eye means: Given 2 photo- (A) and (B), can you immediately tell which photo is (A) and which photo is (B), say within 3 sec?

Theorectically, it seems correct, just that in real life, optics, lens, sensors are not made proportionally equal. In all depends on quality. In simple terms, a 6mp may give you the 6 times megapixel over a 2mp, but it may not resolve the details as clearly as you want it. :)
 

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