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Old Nov 30, 2005, 12:23 PM   #1
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What is the difference between cropping an image in Photoshop or whatever or using the resolution reducer feature on camera like DX2 or FZ30 ? I am wondering if by increasing the focal lengh and reducing the resolution in the camera we are doing what can be done with software. Maybe I am all wet ?

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Old Nov 30, 2005, 12:50 PM   #2
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Not sure what you are talking about with reducing the resolution in the camera. If you are talking about reducing the resolution by using a digital zoom, then it is about the same as cropping the image in an editor.

Going to a lower resolution before zooming doesn't make much sense otherwise.

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Old Nov 30, 2005, 3:09 PM   #3
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Panasonic FZ 30 has a feature that allows the res to drop and increases the multiplication factor therefore boosting the focal length. It is a 12x zoom at 8 megs, a 15X zoom at 5 megs and a 19X zoom at 3 megapixels. If I shoot a hawk at 100 feet at 12X and then switch to 19X (3 megapixel ) mode, the hawk will look closer but will it still have the same number of pixels on the bird whether I crop from the 8 meg photo or leave the 3 meg alone?? It is somewhat confusing.
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Old Nov 30, 2005, 3:34 PM   #4
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it sounds like basically it allows you to use smaller area on the sensor to increase your "crop factor". If the object in the end covers the same area on the sensor then I guess the res will be the same. My own question is that the difference between this and the "digital zoom" on the normal digital camera is that this doesn't boost the resolution to the regular size, therefore the image quality per unit area on the frame remains the same but with smaller pic?

Why would you do this though, if you can just take a full size image and crop it yourself afterwards, which also allow you to recompose the image by how you crop it right? Which I guess answers your question since this is basically what you can do in post processing...
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Old Nov 30, 2005, 3:54 PM   #5
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The Nikon D2x has the same feature. It is a 12 meg camera that can be switched to 6 meg to double the focal length of the lens instead of the normal 1.5X. This is a $5000 camera. Why add the feature if it serves no purpose?
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Old Nov 30, 2005, 5:36 PM   #6
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Does the D2X double the focal length at 6MP, or double the "1.5x" at 6MP, which means effectively tripling the focal length?

At any rate, I still think the purpose of this function is redundent, as you can crop the uncompressed pic afterward anyway withno loss of quality, and you can probably make better judgement and select what you want to keep in your frame, than shooting a cropped frame to begin with. I can see though with the D2X with its bigger sensor it can be useful when you don't have that long telephoto lens you can use this function as a backup, and still take a decently big pic with good quality....
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Old Dec 1, 2005, 7:10 AM   #7
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The reason the D2X has it is so that they can double the frame rate up to 8.5fps and put lots more images into the buffer.

Useful for sports & photojournalism I suppose.

It's just an in-camera crop so it doesn't change the EFL as such. Of course if you blow the reduced size image up to the same size as an equivalent shot at full resolution then you are changing the EFL.
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Old Dec 1, 2005, 3:02 PM   #8
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Let us back up...

1. The focal lenght mulitplier, or cropping factor is vaguely equivalent to zooming. Most of us call it an increased zoom, but this is not quite true.

Let us say that you are shooting with a 2x croping factor. The actual zoom remains the same, but you are doubling the number of pixels on the target image. It's NOT a real zoom, but since you are increasing the pixels on target, it has some strong advantages for the the wildlife and sport enthusiat.

Compare this with film where there is no sensor. If you did a cropping factor with film, you would gain NO benefit, since film has a fixed ability to resolve detail, whereas with digital the amount of detail is a reflection of the MP's.

2. Optical zoom is simply the actual zooming capability of your lens. If you have a 10x lens, then you are ten times closer to the subject. This is an actual, or if you will - True zoom.

Whereas "Digitial zoom" is the software in the camera interpolating the image up. As a number of people have pointed out, different camera's have different ways of approaching this - But if it's digital zoom - then it's software zoom - Interpolation. Is it a good thing to use?

Depends on the capability of the camera's software algorhytm. Take some shots at your maximum optical zoom, take some comparison shots with digitial zoom.

Then load them into your favorite software program, and interpolate your optical zoom up to the size of the digital zoom. Which is better? If there is no gain from THAT cameras digital zoom - why bother? In my personal experience, Photoshop does a better job at interpolation then the digital software of the camera's I've used - But I've hardly used them all, so test this out for yourself!

3. The crop of the D2x has nothing to do with any of these points. The D2x simply crops away part of your image AND your MP's to achieve a faster shooting rate.

So you are actually using only 6 MP's of a 12 MP camera. So the ONLY gain is a faster shooting rate - which in some situations no doubt comes in quite handy.

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