The mega pixel myth?

[luisr]

Originally Posted by surfnron

ISo an optical zoom of 10X should give a sharper image than a 10X digital enlargement.

Am I right?

Yes. When you use optical zoom, the camera is using the entire sensor (all of its pixels) for a zoomed image. When you use the digital zoom you are only using a small portion of the sensor (less pixels). The image looks zoomed because the camera blows up the small resulting image to the size of the entire sensor.

With optical zoom alone, then the quality of the lens takes more importance.

[voxmagna]

But if you had 10X more pixels than you needed for a standard print, would you get the same or better quality without the optical zoom lens, in a lighter more compact camera?

[Grand Dizzy]

I just want to say that I'm totally gobsmacked.

Following kcemb's suggestion, I took two photos of the same scene. One with no zoom and one at full (3x) zoom. I never thought for a minute this would happen, but the objects in the photo are approximately three times wider at 3x zoom!

In other words, a 3x zoom makes objects nine times bigger.

So it seems I was wrong all along and BillDrew and everyone else were right! Of course I can understand now how square roots come into it, if the zoom factor affects the width of the photo and not its area.

All I can say is that I have been grossly misinformed. I have heard it said (and read) over and over than the zoom factor refers to the size of objects. If you zoom in 10x then objects appear 10x bigger. Not taller. Not wider. Bigger.

I'm actually quite annoyed that there are so many people out there spreading false information about zoom factors. I've read statements such as: "a 2x zoom makes objects appear two times bigger" several times.

I have always been convinced that a 2x zoom means that you can fit twice the amount of picture in, not four times the amount!

I had decided this long ago because when I was a lad (about 15 years ago) I had a camcorder with 6x zoom and when I first got it I wondered if "6x zoom" meant 6x the dimensions, or 6x the area, so I experimented and found that the camera was zooming into an area one 6th of the full area. I guess the manufacturer must've been using a different terminology to the one that is most popular.

Anyway. I'm absolutely delighted to find that 3x makes objects 9 times bigger. Because, using my old definition of what zoom means, I now have a 9x zoom camera!

I don't use the zoom very often, otherwise I may have noticed this before.

Anyway, I really should reply to people's posts:

Originally Posted by BillDrew

You are free to define things the way you want as well as living under the bridge with the other trolls.

I don't get the reference. ??? Or are you just insulting me?

Originally Posted by luisr

When you crop, YOU are doing the zooming and loosing information in the process. The cropped image has less pixels than the original.

Come on, I'm not stupid. I realise that by cropping an image down, I'm reducing the number of pixels it has!

I never said I thought I could take 2272x1704 photos at 9.5x zoom. I said that my camera can take 2272x1704 photos at 3x zoom, but if I crop them down to 1280x960 then I can get a 9.5x zoom.

I realise 1280x960 isn't as good as 4 megapixels. But 1280x960 is still not an awful resolution. It's bigger than most computer screens.

Note that this was before I discovered I was wrong about zoom factors. Using my newly adjusted concept of what zoom is, cropping my photos down to 1280 would give me a zoom of 1.8x. Which, when combined with my 3x optical zoom would give me just over 5x zoom.

Although I have to say I don't really care about trying to increase my zoom anymore, now I know that my 3x zoom makes objects three times their original width, and not just three times bigger.

Originally Posted by eric s

First off, I just want to be clear. I’ve seen you answer some other questions in very intelligent ways. I’m keeping at this so that we can get to the bottom of it (for the records) and so we don’t annoy you enough to drive you away. Personally, I’d rather you stayed. Forums like these only thrive when people with knowledge share with others that don’t have it. I hope we aren’t bothering more than a normal disagreement between people does.

That's a good attitude to have. Don't worry, nobody here is annoying me. I've found all your comments interesting and, as a result of this conversation, have learnt something extremely important about zooming. Thank you all!

Originally Posted by eric s

You never commented on either kcemb’s or my posts. Did you read them? I made points and asked questions which you didn’t answer or touch on

My apologies. I read every word that everyone said. I just felt a little confused and overwhelmed with things to reply to. And I wasn't sure how to reply to certain things as I'd gotten quite confused about what we were talking about. So I instead decided to go back to the beginning and readdress the original statement that threw me. It seemed simpler.

I will answer all the questions you asked me in your most recent post...

Originally Posted by eric s

You only say “crop the image”. Do you really mean this? You do not enlarge the image (through some form of interpolation) to get back to the same number of pixels as the uncropped image? This matters a lot. One way gives you fewer pixels than the other.

Being a guy who deals with all his images onscreen, the only reason I can think of to scale an image up would be if I needed to print it out and I didn't think the dpi was high enough. In which case I would make a copy of it and scale up the copy. Scaling an image reduces quality slightly, quality that you can never get back, so you have to work with a copy, unless you know you'll never need the original again. Being an "onscreen" guy, the original is all that matters to me.

I also don't see the need to store a 1 megapixel image at a 4 megapixel filesize. Keeping a "scaled up" version of a photo on my hard drive seems pointless, when the original contains all the information and is much sharper.

Originally Posted by eric s

Mike_PEAT described how cropping just looses data. Did you agree with his description of how to simulate a crop physically and comparing it with what a zoom does?

I read it, and I understood it, but I found it irrelevant. I agree that blocking out areas of your field of view is definitely not the same thing as zooming. But we're not talking about the human eye, we're talking about photos. And when you chop a photo down to a tiny piece of its original size, you're going to bring the remaining piece closer to your eyes to look at it.

All the photos on my hard drive are all kinds of different sizes. Some are many megapixels; some are 300x300 gifs I downloaded from the Web. But I don't tend to look at them at their original size, I tend to stretch them to fit the screen. If I looked at them at their original size, some would be unviewable and some would be off the screen.

Originally Posted by eric s

Does everyone include you? I assume not, but I want to be sure/clear.

You assume correctly. I think cropping provides the same effect as zooming. My view of that hasn't changed.

Originally Posted by eric s

When you "zoom" your camera, you always produce a picture of a given MP. If you crop (and only crop) a picture, you loose data. You do not have the same size picture. It isn’t fare to say that if I crop, I have the same as a longer zoom… you have a smaller picture with less data so they are not the same!

The quality only seems lower if you are remembering the original size of the photo. Yes, data has been lost, but that doesn't mean the photo hasn't been "zoomed". The zoom is successful; it's just at a lower resolution.

Originally Posted by eric s

This is the first time you have ever mentioned interpolation. You changed the ground rules between “the scanner example” and “the camera and crop” example. Please do not do this when forming arguments. Your scanner example is an interesting one, and I’ll talk about that if you want. But it's not the same situation as everything else that has been discussed.

I realise scanners and cameras are different thing.

I mentioned scanners because I was making the pont that having more pixels doesn't make an image better quality. Scanners often provide higher resolution scans - but the scans are no better quality, they're just lower resolution scans that are scaled up to a higher resolution.

I thought this was an important point to make, because I was trying to explain how a higher resolution photo could, in theory, be lower quality, if the resolution of the CCD had a limit, and the camera was just scaling images up, like scanners do. In which case, taking lower resolution photos would yeild higher quality photos, because there would be no interpolation occurring.

Originally Posted by kcemb

If you do not zoom, but take the same picture at wide angle then crop a 1600x1200 image to get the same picture as the optically zoomed image, so that the result is a picture of 800x600 pixels, or items of information, then that is all the information you have to deal with.

I realise 1600x1200 is better than 800x600. I never said lower resolution was the same as higher resolution. I just speculated that if I was prepared to go down 1.2 megapixels then I could have a 9.5x zoom.

When 1 megapixel cameras were the highest anyone could get, then a camera that takes 1.2 megapixel photos at 9.5x zoom would seem like a good thing. Just because there are now higher resolution cameras available doesn't mean that 1 megapixel photos are useless. As I explained above, many computer screens are lower resolution than 1280x960, so these photos would at least be useful for on-screen viewing.

For example, I could take 1280x960 photos of birds at 9.5x zoom, and put them on a website for people to download.

Again, I should point out that I'm now aware that zoom factors don't relate to area - they relate to dimensions.

[Mike_PEAT]

Originally Posted by Grand Dizzy

In other words, a 3x zoom makes objects nine times bigger.
...
Anyway. I'm absolutely delighted to find that 3x makes objects 9 times bigger. Because, using my old definition of what zoom means, I now have a 9x zoom camera!

:roll: Zoom is not a definition of size...zooming is only an action, and not all 3x zoom cameras are created equal. Zoom is a ratio of the camera's widest angle to the tightest telephoto. My own camera is 5.9mm to 59mm (38mm to 380mm in 35mm film format)...IOW, 10x.

One more time, merely cropping an 8x10" photo to 4x5" doesn't make a zoomed in photo...unless you then enlarge that cropped photo back up to the original size of 8x10", in which case you are doing a "digital zoom".

[Grand Dizzy]

Originally Posted by Mike_PEAT

One more time, merely cropping an 8x10" photo to 4x5" doesn't make a zoomed in photo...unless you then enlarge that cropped photo back up to the original size of 8x10", in which case you are doing a "digital zoom".

Okay then, it's a digital zoom. But it's much better quality than a digital zoom because I'm not scaling it up. Digital zooms are rubbish.

Funny, I tried to write a word that means the opposite of "blow", but it censored it. Is "s*ck" a swear word now?

[eric s]

This forum package is a little aggressive on its censoring. I've wanted to use that work as well, but it doesn't let me... so I just write around it.

I agree on the digital zoom being rubish. Some people have made a decent argument in their favor... because some cameras without a raw format will do the digital zoom in camera before the jpg compression happens. Since all in-desktop-computer digital zoom on a jpg will happen after jpg compression, there is something to said for that argument.... but I'd still take an optical zoom any day (and I'm will to pay for it.)