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Old Aug 11, 2012, 2:13 PM   #1
seb
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Default zoom vs sensor/glass

Will someone please explain - or suggest links with comparison photos - quality of photos of a distant subject 'blown up' from a zoomed P&S (small sensor large zoom) vs a better sensor but lower zoom. For example, a mountain goat on a hillside at several hundred yards. Take the same picture with a Nikon P100 at full zoom and an Olympus EP3 with stock 14-42mm. At home blow up just the goat to an 8X10 print - what's the result/difference? The specific cameras above are not my and I recognize that the real world differences can vary greatly among camera pairings but hopefully the spirit of the question comes through. Basically, I want to better understand the effects of digital (post acquisition) zoom from an image from a higher quality camera vs the optical zoom of smaller sensor/high zoom P&S. Are there any sites showing images where I could see this sort of comparison, maybe from a variety of cameras?
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Old Aug 11, 2012, 4:12 PM   #2
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However you get the image, all optical zoom is better than any digital zoom.

If you capture a 16MP image with a 35mm equivalent focal length of 200mm, and crop it to 1/2 size, it will look just like an 8MP image with a 35mm equivalent focal length of 300mm. Digital zoom will try to take that same 8MP image and upsample it to 16MP. The quality of the image depends on the quality of the upsampling algorithm. Most cameras don't have the processing power to do a good job, so upsampling is best done in post-processing, and in multiple small steps instead of one big step.

Depending on the circumstances, an upsampled image can look as good or better than a native image, but that's rare, and never comes straight from the camera.

See Digital Zoom.
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Old Aug 11, 2012, 4:55 PM   #3
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I see where you're going with this seb... and it might be an intriguing test- but there are many variables- possibly the most important one being the native resolution of the bigger sensor camera. The higher the resolution of the DSLR, the better chance of it putting up a fair fight.
Nikon's 24mp D3200 might be able to take on the P100 in this battle...!!!

My guess is,however, that if a said image taken at full zoom with the P100 is not cropped in any way- and the D3200,using kit lens,image is cropped to match the image of the P100- then I'd go with the P100- though I may be wrong..!

If,however,the DSLR you choose to compare is of similar resolution, then there is no way the DSLR would stand up- the resulting image would just be too small and would lack sharpness and resolution.
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Old Aug 11, 2012, 5:59 PM   #4
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G'day seb

Great Q mate - keep on thinking this way

In recent years I have done lots of this sort of testing & both TC and Simon are on the money with various bits of their responses

TC says "The quality of the image depends on the quality of the upsampling algorithm... "
and Simon offers "... if a said image taken at full zoom with the P100 is not cropped in any way- and the D3200,using kit lens,image is cropped to match the image of the P100 ..."

I have owned digi cameras which could use their internal digital zoom capabilities and produce very, very sharp prints of 8" x 12" with little signs of pixellation. These were early model 3mpx cameras with a 'basic' 10x optical lens

I have never been able to replicate the results with recent cameras > so I am left to presume that the maker's algorithm for in-camera upsizing and jpeg auto-saving were very smart

I will post more when I can find the materials > time is beating me at the moment
Regards, Phil
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Old Aug 11, 2012, 6:09 PM   #5
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I have a photo I took with a 3MP Nikon CoolPix 880, cropped to about 2MP, and printed at 8x10. It's hanging on the wall of my dining room, alongside a similar 8x10 captured on 35mm film. You need an eye loupe to tell which is which.

sed wants to see comparisons on-line.

There aren't any. And even if there were, they would be meaningless, because there are too many variables.
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Old Aug 12, 2012, 6:28 PM   #6
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G'day again seb

Several other thoughts - and again TC & Simon are pretty much 'on the money' with their offerings as well
Back in 2006-7 I took a series of test pix to check the difference between optical & digital zoom stuff - I have searched for the images without success > time has moved on. But essentially I had a 3x zoom good quality Olympus vs my 10x zoom Fuji - 2 cameras of same-sized sensors but I could do a side-by-side printed test for comparison purposes. I photographed several scenes at 1x then 3x then 6x then 10x with both systems > ie- the 6x & 10x on the Olympus were digital zoom pix

When printed and placed side-by-side, one can easily see the image-sharpness differences between the optical zoom vs the digital zoom from the smaller lens. Not a huge difference, but it was there

A couple of years ago I bought a Pentax, thinking that its larger sensor would give me better image quality than the smaller sensor used in superzoom cameras. I was quite disappointed > there was damn-all difference between the Pentax with its Sigma lenses and the old Panasonic FZ30 with its Leica 12x zoom lens

In recent weeks I have done a series of test prints evaluating the lens sharpness & quality of my new Fuji X-s1 > from this I am printing 20" x 30" prints and when showing them to people they cannot believe that they have been taken with a 'small-sensor' camera rather than a dSLR with its larger sensor

Bottom line - a very good lens will always "bring home the bacon" as the old saying goes > a crappy lens will always disappoint, no matter what is behind it in sensor size / shape / recording quality

Regards, Phil
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Old Aug 12, 2012, 8:24 PM   #7
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What matters more that the camera, lens, or sensor resolution is the upsampling algorithm that the printer driver and/or the imaging application uses. If you want to compare the actual images, you need to do it on your screen before they get upsampled by your printing routine.

But the images must be of the same detail at the same resolution. If you need to scale one image more than another in order to see the same detail at the same relative size, then the upsampling algorithm used by the imaging application and or OS with kick in, and throw off your comparison.

That's why I said that there are too many variables to be able to do what sed wants.
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