Digital Zoom vs. RAW, Crop & Resize?

I know that most people on these forums see Digital Zoom as the Anti-Christ, but I have also heard it said that it's ok to use digital zoom if you are going to have to crop an image anyhow because it allows you to crop the image before you add JPG artifacts.

In my case, I'm experimenting with extreme macro shots using reversed SLR lenses. Even at full optical zoom I still get a tunnel effect that I need to crop out. So I've been using a little digital zoom to accomplish this. (I know I could buy SLR lenses that wouldn't give me as much vinietting, but these ones were free).

So my question is, would there be any advantage to shotting with out digital zoom but in RAW mode and then cropping and resizing the picture later in Photoshop or some other program? I guess what I'm really asking is if Photoshop does some kind of voodoo when it resizes a picture that makes it better then cropping it in camera? It sure seems like a lot more work.

I would set up a test to see for myself, but I don't actually have Photoshop at the moment; I'm using MS PhotoDraw for now.

Thanks!
-Brian

Rather than rewrite what I just wrote, please see the thread below:
http://forums.dpreview.com/forums/read.asp?forum=1010&message=5292046

Bowkerhouse said:

I know that most people on these forums see Digital Zoom as the
Anti-Christ, but I have also heard it said that it's ok to use
digital zoom if you are going to have to crop an image anyhow
because it allows you to crop the image before you add JPG
artifacts.

In my case, I'm experimenting with extreme macro shots using
reversed SLR lenses. Even at full optical zoom I still get a
tunnel effect that I need to crop out. So I've been using a little
digital zoom to accomplish this. (I know I could buy SLR lenses
that wouldn't give me as much vinietting, but these ones were free).

So my question is, would there be any advantage to shotting with
out digital zoom but in RAW mode and then cropping and resizing the
picture later in Photoshop or some other program? I guess what I'm
really asking is if Photoshop does some kind of voodoo when it
resizes a picture that makes it better then cropping it in camera?
It sure seems like a lot more work.

I would set up a test to see for myself, but I don't actually have
Photoshop at the moment; I'm using MS PhotoDraw for now.

Thanks!
-Brian

Click to expand...

Thanks for the reply, but I'm still curious if Photoshop has a better process for enlarging the section of the CCD that digital zoom crops down. If I can get a hold of a copy of Photoshop here in the near future I'll see if I can do some tests.

If anyone already has knowledge about this I'd love to hear your thoughts!

-Brian

In my playing around, I haven't seen that PS is any better at it than the camera is. If I was forced to choose, I'd say the camera does a better job.

Bowkerhouse said:

Thanks for the reply, but I'm still curious if Photoshop has a
better process for enlarging the section of the CCD that digital
zoom crops down. If I can get a hold of a copy of Photoshop here
in the near future I'll see if I can do some tests.

If anyone already has knowledge about this I'd love to hear your
thoughts!

-Brian

Click to expand...

There is a little trick I learned from reading Scott Kelby's most recent book 'Photoshop for Digital Photographers'. If you increase the document size by 10% (110%) repeatedly rather than just jumping up to say 300% it show no degradation. It's true I tried it and blew up a picture from my 30 to poster size and it printed very very well!

Hope that helps...

Bowkerhouse said:

Thanks for the reply, but I'm still curious if Photoshop has a
better process for enlarging the section of the CCD that digital
zoom crops down. If I can get a hold of a copy of Photoshop here
in the near future I'll see if I can do some tests.

If anyone already has knowledge about this I'd love to hear your
thoughts!

-Brian

Click to expand...

From my Canon S30 that is not my '30'. oops

framer said:

Hope that helps...

Bowkerhouse said:

Thanks for the reply, but I'm still curious if Photoshop has a
better process for enlarging the section of the CCD that digital
zoom crops down. If I can get a hold of a copy of Photoshop here
in the near future I'll see if I can do some tests.

If anyone already has knowledge about this I'd love to hear your
thoughts!

-Brian

Click to expand...

Click to expand...

Bowkerhouse said:

Thanks for the reply, but I'm still curious if Photoshop has a
better process for enlarging the section of the CCD that digital
zoom crops down. If I can get a hold of a copy of Photoshop here
in the near future I'll see if I can do some tests.

Click to expand...

IF the camera interpolates from the raw CCD data, then it might do a better job with digital zoom than you could do manually after it's been converted to full color pixels. But I don't know. I'd be curious to know too.

No, I like it! I have an S30 also, which I will now call my '30.

framer said:

framer said:

There is a little trick I learned from reading Scott Kelby's most
recent book 'Photoshop for Digital Photographers'. If you increase
the document size by 10% (110%) repeatedly rather than just jumping
up to say 300% it show no degradation. It's true I tried it and
blew up a picture from my 30 to poster size and it printed very
very well!

Hope that helps...

Click to expand...

Click to expand...

Well that's really good to know! I will see if I can run a comparison test this week, and I'll resize in increments like you suggest.

-Brian

framer said:

There is a little trick I learned from reading Scott Kelby's most
recent book 'Photoshop for Digital Photographers'. If you increase
the document size by 10% (110%) repeatedly rather than just jumping
up to say 300% it show no degradation. It's true I tried it and
blew up a picture from my 30 to poster size and it printed very
very well!

Hope that helps...

Click to expand...

Ok, so I did a test between using digital zoom to crop a picture in camera and using Photoshop to crop and resize a RAW image. The picture results can be found at:
http://groups.msn.com/BowkerHouse/resizingcomparisons.msnw

I used three methods; the first was to use digital zoom to crop and resize the picture in camera, the second was to use Photoshop to resize the RAW image data in one step, and then third was to use Photoshop to resize the RAW image data in many small steps, 10% at a time.

Digital Zoom: This method produced the softest image, but also had the smoothest color. Depending on the user's preference this could be the desired effect of the three.

Photoshop in One Step: This method had the most pixelation but did have sharper edges. (Perhaps too sharp for some.) This was my personal least favorite of the three.

Photoshop in 10% Steps: This method was the sharpest of the three, and did not suffer from the pixelation of the second one. The edges did seem overly sharpened, however, and the color was the least smooth. It was a lot of work to do it this way.

Conclusion: Resizing in Photoshop using multiple small steps is pretty clearly a better technique then resizing all in one step. But when compared to digital zoom it's more a question of preference: Do you want soft, evenly colored images, or are you looking for the sharpest possible edges? My guess is that most of the time most people would choose the Photoshop method if they had to zoom in real far or blow up a print (but optical zoom is of course still the best way to go).

-Brian

Interesting. I would have never expected the multiple resizes to look better than a single one. I'd be interested to know how a RAW + crop/resize would compare if a better interpolation algorythm was used, such as Qimage's vector, or even the built in interpolation in BreezeBrowser (which they claim is better than Photoshop).

With my S30 one can't use digital zoom when in raw mode. How do other models compare?
Paul

Darin C said:

Interesting. I would have never expected the multiple resizes to
look better than a single one. I'd be interested to know how a RAW
+ crop/resize would compare if a better interpolation algorythm was
used, such as Qimage's vector, or even the built in interpolation
in BreezeBrowser (which they claim is better than Photoshop).

Click to expand...

Darin C said:

Interesting. I would have never expected the multiple resizes to
look better than a single one. I'd be interested to know how a RAW
+ crop/resize would compare if a better interpolation algorythm was
used, such as Qimage's vector, or even the built in interpolation
in BreezeBrowser (which they claim is better than Photoshop).

Click to expand...

--

I'd be interested too. I always shoot raw, and use Powershovel2 to convert to TIFF. I never interpolate in photoshop after I crop but rely on Qimage to produce depixelated prints.

I think that raw + Powershovel2 produces the sharpest images with most detail.

Jonathan (also with S30)

martinpd said:

With my S30 one can't use digital zoom when in raw mode. How do
other models compare?
Paul

Click to expand...

Can't on my S50 either, but that's to be expected. Since a RAW image is the data as it comes off the CCD, resizing and interpolating that data (which is what you do when you use digital zoom), would by nature, no longer be RAW.

But brings up a question I raised in another thread ( http://forums.dpreview.com/forums/read.asp?forum=1010&message=5283151 )... I have seen threads reporting that, for example, a 4MP camera set to output a reduced pictures size of 1600x1200 will yield a better picture than a 2MP camera outputing at it's native resolution of 1600x1200. That goes against what I would inititally expect. I'm assuming, therefore, that the interpolation is happening at the raw level, so the higher pixel count is helping when the bayer interpolation comes in to play. So my question is, do any of the RAW processing applications also do resizing at the raw level, to allow you to get better output of reduced sized photos than if you first converted the full size raw file, and reduced later?

1) Zooming in digitally decreases your feild of view, which makes it unessesary hard to follow a moving object compared to cropping later.

2) When making the shot, you may not have much time to decide how to frame the digitally zoomed object perfectly. In the computer you have all the time in the world to do the optimum cropping.

regards

HAL