Upsizing/Downsizing files from scanned negs.

[catem]

I always understood that if you save a file as a TIFF you can upsize and downsize without loss of quality, and for that reason I have been in the habit of 'storing' files at a lower resolution/size than I want to print them.

Have I got this wrong?
I do keep most originals of scanned negs at full res in separate folder, but when I compare them with files that I've worked on and resized (made as large as the original again) the files I've worked on sometimes appear to have lost quality.

I re-size using photoshop (bicubic).

[Dave Miller]

I always understood that if you save a file as a TIFF you can upsize and downsize without loss of quality, and for that reason I have been in the habit of 'storing' files at a lower resolution/size than I want to print them.

Have I got this wrong?
I do keep most originals of scanned negs at full res in separate folder, but when I compare them with files that I've worked on and resized (made as large as the original again) the files I've worked on sometimes appear to have lost quality.

I re-size using photoshop (bicubic).

I rather think you have.

When you downsize, your software discards information; it's gone for ever.

When you upsize, your software invents information to fill the gaps in your streached image. What you get is a degraded image.

Always scan and store at maximum resolution.

[Baxter Bradford]

I agree with Dave. Sadly you have had the wrong end of the stick. When resampling downwards, 'bicubic sharper' seems to work well, or use Bicubic and then apply USM to your taste.

Suggest also working with 16 bit files and again switching to 8 bit once all work is finished ready to hit print button. Again apply 'output sharpening' dependent on the output device. Look at the Pixel-genius photo-kit sharpener Pshop plug-in. A great asset to have, but be prepared to modify std settings to your taste.

[jd callow]

Dave is correct. In a perfect world you would scan at your scanner's max optical res and largest colour space. colour correct or adjust the contrast and density (doing this on adjustment layers is a safe way to go) and spot the image, then save it as the 'master' for all future copies.

No file can be rotated (other than in increments 90 degrees) or sized (up or down) without some loss or 'invention'. Similarly, colour profiles and adjustments to curves or levels can cause the irreplaceable loss of information. I would investigate and use the widest gamut profiles for your 'master' files and be very careful about 'clipping' the histogram when adjusting tones, contrast or colours (hence the recommendation of the adjustment layer).

When you make copies of the master use the appropriate profile (adjust as need to accommodate the new profile) and size to taste. There is a lot of very good information about sizing images on the web. I use a simple technique which works fairly well. I size the image in small steps (anywhere from 10 -20% of the current image size) and apply a small amount of USM between steps.

[catem]

I rather think you have.

When you downsize, your software discards information; it's gone for ever.

When you upsize, your software invents information to fill the gaps in your streached image. What you get is a degraded image.

Always scan and store at maximum resolution.

I thought this was true of Jpegs but not TIFFs. I thought with TIFFs you didn't get interpolation unless the original file was less than what you were upsizing to. Hmmmm - does make sense though.

Oh well - at least I have all the originals
And I guess my small Jpegs for emails etc are O.K.

So - does this mean you do all your editing at maximum res?

[catem]

Dave is correct. In a perfect world you would scan at your scanner's max optical res and largest colour space. colour correct or adjust the contrast and density (doing this on adjustment layers is a safe way to go) and spot the image, then save it as the 'master' for all future copies.

No file can be rotated (other than in increments 90 degrees) or sized (up or down) without some loss or 'invention'. Similarly, colour profiles and adjustments to curves or levels can cause the irreplaceable loss of information. I would investigate and use the widest gamut profiles for your 'master' files and be very careful about 'clipping' the histogram when adjusting tones, contrast or colours (hence the recommendation of the adjustment layer).

When you make copies of the master use the appropriate profile (adjust as need to accommodate the new profile) and size to taste. There is a lot of very good information about sizing images on the web. I use a simple technique which works fairly well. I size the image in small steps (anywhere from 10 -20% of the current image size) and apply a small amount of USM between steps.

We were posting at the same time, thanks.

I have to confess some of this is new to me (e.g. loss of info through rotation). I have just recently come across the idea of changing size in increments. Thanks I've obviously got a bit of research to do, but at least it explains why I've been having to revert back to the originals :rolleyes:

[jd callow]

So - does this mean you do all your editing at maximum res?

"In a perfect world"

Time is the limiting factor.

[steve]

If you want to upsize a file, the stepped method works the best. Make an action with a 10% step in upsizing . Use "bicubic smoother" as the resample method. Assign the action to a function key.

Now, all you have to do is just hit the 'F' key until you get 1 step OVER the size you need. Now, downsize using "bicubic sharper" to the exact size you need. This method seems to work as good as the dedicated resizing programs.

When downsizing, you can go directly to the exact size you need in one step. Use "bicubic sharper" for down sizing.

If you work in 16 bit TIFFs and then convert to whatever file format you want after sizing, you will get the maximum quality. The problem with trying to re-size JPEGS in steps is that it seems to emphasize the JPEG artifacts at every step. I've had better results resizing JPEGS in a single step.

[donbga]

So - does this mean you do all your editing at maximum res?

Yes edit a maximum res and then resize as require. Interpolation using the spline algorithn will yield the best results but you will need to get other applications that support spline, such as Qimage and PhotoZoom Pro.

Stair step interpolation really doesn't provide any advantages that the new CS and CS2 rezize algorithms provide.

Just remember to always edit a copy of your original and in 16 bit.

Don Bryant