Is hi-res + shrink better than taking lo-res?

If i take pictures in hi-resolution 1600X1200 and then shrink to
800X600 is it better quality to just take picture in 800X600 mode?

 

In a word, no.

Unless cramped for disk space, take highest possible resolution and
downsize later for various purposes.

 

On a similar note, is it better to use digital zoom or to just crop
later? or is this just chicken or the egg?


Eric

 

I'd never want to use Digital Zoom for anything. I'd take the
pic and save the original and crop later and then saveas that
cropped file to a different name.

 

Digital zoom is nothing more than in-camera crop and enlarge. You
don't gain anything at all, really, except a larger image of a smaller
portion of the sensor.

--
You need only reflect that one of the best ways to get yourself a
reputation as a dangerous citizen these days is to go about repeating
the very phrases which our founding fathers used in the struggle for
independence.
-- Charles A. Beard

 

Yes and no. It really depends on the noise level of the image. Shooting say
a 6MP image and resizing it down to 800x600 will give you a better picture
(noise wise) than shooting it at 800x600. The reason is the reduction in
size basically squeezes out most of the noise.

ljc

 

Digital zoom is crap. If you have the MP but need to make the image look
like you had more optical zoom you are better of cropping later than fooling
with the digital zoom. The digital zoom resample's your image to work its
magic. Cropping doesn't resize it just cuts away.

ljc

 

And a nice hit in overall picture quality.

ljc

--
Do not assume that because I didn't reply to your comments that you are
correct or that I am wrong or that I am correct and your are wrong. You
can assume that you bore me!

 

When I had to resize a few relatively small images for my job to a smaller
size and the resize dimensions were pretty close to the original ones, I
used the following trick. If your computer RAM allows you to do that then
you can try it but it can take some time. Less RAM, longer transformation
because in this case it will involve the hard drive.

First of all if you resize these images in one step up or down you'll get a
very bad quality of the target images if the sizes can't be divided by 2, 3,
etc. Try to increase the original image in a few times, depending on what
the computer you have keeping in mind that 2 times increase really increases
your picture in 4 times because of 2 dimensions, and only then decrease to
the target size. For example if you have the original image like 500x300
pixels try to increase the image up to 5000x3000 and then decrease to, say,
80% from its original size. You will see the difference comparing to the one
step decrease. Also I'd increase not in 10 times, but in 3, 5, 7, 9, or 11
times, etc. to preserve more thin lines. That's my own feeling based on some
mathematics and geometry. I don't think anybody needs the theory here.

Just D.

 

The answer to both parts is that resizing later and cropping
later give you more control than having the camera do the
tasks. Taking the photo at maximum resolution does make the
file sizes larger, but that won't matter much for most
photographers. Hard drives and memory cards are both low in
cost. I just bought a 160 GB external HD for $50 after
rebate, and not long ago I got a 1 GB memory card for $20
after rebate. And yesterday I saw a 1 GB memory card for
that price, without the need for getting a rebate.

 

If i take pictures in hi-resolution 1600X1200 and then shrink to

It depends on how much you lose in JPEG compression. If you compress
the 1600x1200 image, then uncompress it, scale it, and recompress it,
you'll probably end up worse than if you'd just shot at 800x600. If
you use your camera's "fine" JPEG setting, though, you probably won't
lose much, and you may gain a lot of you decide you want to crop the
1600x1200 image instaed of shrinking it.

-Joel

 

On a similar note, is it better to use digital zoom or to

I've also never used the digital zoom, but, again, depending on JPEG
compression, the digital zoom may give you better results than
cropping after a round of compression and uncompression.

-Joel

 

This pretty much flies in the face of at least conventional wisdom. On
what basis to you speculate??

 

Yes, but as the Dr. says, "Don't do that."
If

Even if one is merely downsizing the resolution and/or number of pixels,
one is best off starting with the highest resolution the camera is
capable of.

Joel- in my question of you upthread, there's a typo....

 

I've also never used the digital zoom, but, again, depending on JPEG

If you are going to crop the image anyway, so that, either way, you'll
only be using --- let's say --- the middle 50% of the sensor, then you
have two choices:

1. Take the information from the entire sensor, JPEG encode it, JPEG
decode it, take the middle 50%, and then re-encode it. There's no
way you can avoid getting some noise from the outer part of the
image (which you aren't even using) and there's no way you can
avoid the degredation from the JPEG encode decode.

2. Take the information from the middle 50% of the sensor, and JPEG
encode you. You don't get noise from the part of the image you
don't need, and you don't suffer an encode/decode cycle.

Now, it may be that the noise from the outside of the image is
negligible, and it may be that the degradation from the encode/decode
cycle is minimal, and it also may be that a good computer program
can do a better job upsizing the image than the camera's software can,
but these various assumptions are not obvious, nor, do I believe,
always true.

To take a concret example, if you take a picture of a deer, and the
deer only occupies half of the frame, and you want to a make a 6x8
printed photo of just the deer, you only have 800x600 of image data,
or 100dpi. If your printer prints at 150 dpi, you need to fill in the
missing dots. I don't know if the improvements you can make with
advanced computer software outweigh the disadvantage of encoding and
decoding the image an extra time. I also don't know if the camera can
optimize the upsampling by working with the raw un-JPEG'd data.

-Joel



Joel M. Hoffman, PhD
http://www.lashon.net/JMH

 

I tested this (but some time ago) and found that 2:1 digital zoom was
indeed better than cropping after compression. The larger image in the
viewfinder may also help composition or focussing.

I would suggest testing on your own camera, though.

David