Uprezzing, stair-step

mercphoto

I tend to agree with the people who run Smugmug that uprezzing an image is not necessary when sending prints to a lab like Smugmug. Maybe it is when making big prints at home, I don't know because I don't do it. But I know the common way to uprez is with Bicubic Smoother, going up 10% at a time. I was wondering, due to the nature of binary arithmetic, if going up 12.5% at a time would actually be better? Or is the inherint round-off error of a multi-step algorithm part of the pleasing effect (rather than doing the upsample all in one step)?

cletus

mercphoto wrote:

I tend to agree with the people who run Smugmug that uprezzing an image is not necessary when sending prints to a lab like Smugmug. Maybe it is when making big prints at home, I don't know because I don't do it. But I know the common way to uprez is with Bicubic Smoother, going up 10% at a time. I was wondering, due to the nature of binary arithmetic, if going up 12.5% at a time would actually be better? Or is the inherint round-off error of a multi-step algorithm part of the pleasing effect (rather than doing the upsample all in one step)?

Bill,





Anyone picked up any good image processing algorithm books lately?

ridetwistyroads

All of that either went WAY over my head , or way under.

Shay Stephens

An alternate (rather spicy) view on upsizing
I think the whole stair step process is bogus. I have yet to be able to see a difference between regular old bicubic resampling and all the other fancy shmancy* hoop jumping techniques *in a printed photo*. So in my mind, it's all a waste of time, and the extra steps are just there to make you think you are doing a more workmanly job.

The only time I need to upsample anything is when I am swapping heads on people and the head is too small for the body by a little bit (or similar scaling problems). All the big prints I send out are all sent native resolution, no matter how big I print.


*Fancy shmancy is a term I only pull out when I am rather worked up, uptight and outta sight on a subject. You will have to pardon me

mercphoto

ridetwistyroads wrote:

All of that either went WAY over my head , or way under.

Very briefly, even though one-tenth is a rational number in the decimal world, one-tenth is irrational in the binary world. You cannot exactly represent one-tenth, the best you can do is approximate it. But you can exactly represent one-eighth in the binary world, it is "0.001". One-eighth is 12.5%.

mercphoto

Shay Stephens wrote:

I think the whole stair step process is bogus.

I figured as much. They touted this process as an absolute necessity at a Rocky Mountain School fo Photography weekend I went through. I kinda got the feeling that it was a left-over from the days of 1 and 2 MP cameras. That at today's resolution it was completely unnecessary.

Shay Stephens

Bingo!

mercphoto wrote:

I figured as much. They touted this process as an absolute necessity at a Rocky Mountain School fo Photography weekend I went through. I kinda got the feeling that it was a left-over from the days of 1 and 2 MP cameras. That at today's resolution it was completely unnecessary.