Which file format?

What do you recommend for the best file format to save pictures in and publish in the gallery? Having edited a RAW in Elements there are several options including PDF which ends up as a massive file (120MP+); however if I edit with Picasa PDFs are much more sensible in size. I have been using JPEG and whilst the file size is similar to the original these look small on the screen.

To display in the Gallery they should be JPEG files. If the images look too small then they have been resized too small, so make an image probably not more than 2000 pixels wide.

For the forum, 1000 pixels is better.

The site will resize images that are too large, but the upload time could be very long if you use huge files.

Thanks John, my JPEGs are typically 9 to 12.5 megapixels so upload ok, and that's at the 'maximum' setting in Elements. As an experiment I saved my 'cherry blossom' in both JPEG and TIFF and there is no discernible difference on screen even if you zoom right in, but the TIFF file is over 47 megapixels compared to the JPEG at around 10.

There are two different 'sizes' to consider with digital image files .... first is commonly termed 'dimensions', and is what John was referring to earlier (such as 1000 pixels along one side). Each camera outputs a native file with fixed dimensions, assuming it is set to its maximum output setting .... eg something like 4256 x 31200 or similar (I made that up as an example).

The ratio of height and width determines the actual shape of the photo, and can be expressed as an 'aspect ratio' ... eg 4:3 / 1:16 like with televisions and wide screens.

The other size is the file size. You referred to 9 to 12.5 megabytes before ..... this is massively too much for the internet. These amounts of image data would be suited to high quality printed output. For the web I usually aim for around 1 megabyte, but even less is often OK.

Two things determine the actual file size of an image .... the dimensions combined with compression. The whole point of JPEGs is that they can be compressed drastically without great loss of quality. So, a 9 megabyte file from a camera can be compressed into a 1 megabyte file for web display with no loss of visible quality. Reducing the dimensions for web display also will help too, as a smaller image dimension will need less compression to reach your intended file size (eg 1mb).

Software like Photoshop / Elements offer image sizing dialogues that allow you to control precisely the output dimensions and file size (ie the amount of compression) to create a new JPEG ..... always choose the file option 'Save As' so that you are creating a new file and not overwriting your original.

Both PS and Elements offer a specific 'Save for Web' plug-in (choose from the file menu) that makes it easy to create new resized files for specific purposes.

Every time you 'open' and 'save' a jpeg it is compressed so each subsequent 'open' and 'save' degrades the image slightly'
For printing - saving as 'TIFF' gives the maximum (uncompressed) quality (which can be opened and saved without any loss of quality) but produces larger files'

Just opening and closing a JPEG doesn't constitute saving it. For degradation to occur you would need to open it, alter it and resave it. JPEGs are perfectly satisfactory for printing purposes, and more than satisfactory 9if not required) for the web.

Yes, I think for further 'degradation' to occur some pixel adjustments would need to be made and the compression algorithm run again via the 'save' command, Every time we view a JPEG, even in a viewer window, that is 'opening' the file, so doing that and closing would not cause any change to the file. I guess Michael meant an actual 'save' operation following an adjustment.

I don't print my own photos, but I suppose for commercial output then TIFF might be appropriate. I use an online printing service, and for practical image upload times, I find my 'Max' quality JPEGs to be ideal, anywhere between 6 - 12 mb.

fotoLibra, a large online image library, stopped using TIFF and converted everything to JPEG because that's what magazine and book publishers wanted.

At one time I saved everything as TIFF, but I haven't done that for some years now. Things have moved on.

Yes Nigel, that is what I was referring to, not just opening and closing the image.
By the way....I had an A3 print done by a pro lab and they asked for jpeg, the resulting print was first class and I can't see how a Tiff file would have been any better (although it would have been interesting to see a Tiff print for comparison...maybe something to try?)

For me now, TIFFs are used as 'Master Editing' files ... output from the RAW converter and then into Photoshop as 16bit TIFFs. Here I can use layers, adjustment layers etc galore and save with no compression. I usually flatten my TIFFs as I go and that keeps the file size reasonable. I know that I have a full quality 'master'. This I then use to create new JPEG's from 'Save As' and 'Save for Web', for printing and web purposes.

I am currently keeping and archiving all my DNGs plus the Master TIFFs .... it does take up a lot of space, but I feel comfortable with that as a fall back. The DNGs I feel could be useful if in the future I want to re-do an image, and of course RAW software can improve over time so the results might be better.

Thanks all that throws a lot of light on the issue