Re: I have a 30mp camera redux

David J. Littleboy wrote:
"Wolfgang Weisselberg" <ozcvgtt02@xxxxxxxxxxxxxx> wrote:
Scott W <biphoto@xxxxxxxxxxx> wrote:

But lets look at it another way, say you have your 30MP image, and you
are using your 180 MBytes to store it, now say I have the same image
but at higher resolution, let's say 40MP and I save this as a 6 MByte
jpeg, which image do you think will have more detail, more real
information in it?
That depends a *lot* on the image in question, doesn't it?

Not really. Images aren't random, so tiff is a grossly inefficient means of storing that information. Best quality jpeg is very close to lossless (you really can't tell the difference on prints), and it usually saves more than 50% of the space.

Scott's example isn't very real world. What's more sensible would be to compare, say, an 18MB jpeg (typical of best quality jpeg from photoshop) from a 5D image to a tiff from a 4000 ppi scan of a sharp 35mm slide (preferably of the same scene). The 35mm scan is going to be 72MB, four times larger than the 5D jpeg. But if you print them both at 12x18, the 5D image will look way better.

So the 35mm user has used four times the disk space for a lower quality image. Our hypothetical macho tiff-using film fan is doing something grossly wrong.

I now have an image that has 33% more detail
15% in each dimension. Not really all that much.

Yes. That's why it's a bad example<g>.

Ah, but it is not at all a bad example. The loss from saving in jpeg is very very small, so small they you would have to use something like level 7 or maybe less to lose 33% of real detail.

The people who worry about tiff vs. jpeg seem to want to believe that just the act of saving in jpeg is dumping a ton of detail, but this is just not true.

And this is easy to test, compare say a 30MP image saved as a tiff against the same image saved at a level 8 jpeg but with just a bit more pixels, say 40MP. If the jpeg image has more detail then we know that the level 8 jpeg compression loss less then 33% of the detail.

bump the jpeg level to 12 (figuring photoshop) and even a very small increase in the image size will give more detail.

I know from past test that if I save an image a level 12 jpeg and compare it to the original tiff I can't see any loss in detail, even viewing at 200%. If on the other hand I down size to say 1000 pixel in width compared to 1150, I can easily see more detail in the 1150 wide image, which has about 30% more pixels.

Scott
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