What is the best way of dealing with large JPEGS?

[Garawa]

Hi. I am new to this bit of pictures. I have 120 format negatives of our wedding that have been scanned using a high quality film scanner. I saved the files as high quality JPEGS scanned at 2400 or 4800 dpi as TIFF meant the file size for each was between 500Mb and 1Gb!! They are now around 10Mb each.

These have scanned rather well but some have tiny dust particles which the dust remover function missed and need a little touch up. I can do this perfectly well in Photoshop but that means saving again which is a no-no.

I have tried it and it looks great but am concerned should we wish to request a large print in the future. If I touch up a copy of the picture, what is the best setting. Or if they were scanned at the highest setting, would saving at the highest setting be fine - after all, the majority of the picture hasn't altered. It does create a file size about 20% larger though?!?!

Your thoughts and help is greatly appreciated!

[KeithT]

What I would do (and is what I do) is this. When you have opened your jpeg after scanning, immediately save it as a TIFF, but first resize to 300ppi and a manageable file size, say 3600 pixels long edge. This should give you a file size of about 49.5 mb. Save it as a 16 bit TIFF, scrap your jpeg copy and use the tiff as your non-lossy working file. You can then work on the 16 bit file without deterioration and resize and save as jpegs at either 72ppi for the web, or sized for printing to suit at 250 or 300ppi accordingly. When saving as jpegs from TIFF you will have to change the image to 8 bit. Providing you save your spin-off files in another location, your TIFF file will remain a virgin master. What I have described above is simple to do in Photoshop CS2, which is my present edit programme. You will have to sort it out in whatever programme you are using, but I'm sure it won't be difficult and in fact will be much the same as I do.

EDIT: Give your TIFF masters a working title and keep them in a separate folder. Like wise your web files. I keep a separate folder also for my TIFF 'portfolio' files from which I make all my print files from when needed and also create my low res flickr images from them.

Regards...Keith

[ianpinion]

Originally Posted by Garawa

Hi. I am new to this bit of pictures. I have 120 format negatives of our wedding that have been scanned using a high quality film scanner. I saved the files as high quality JPEGS scanned at 2400 or 4800 dpi as TIFF meant the file size for each was between 500Mb and 1Gb!! They are now around 10Mb each.

These have scanned rather well but some have tiny dust particles which the dust remover function missed and need a little touch up. I can do this perfectly well in Photoshop but that means saving again which is a no-no.

I have tried it and it looks great but am concerned should we wish to request a large print in the future. If I touch up a copy of the picture, what is the best setting. Or if they were scanned at the highest setting, would saving at the highest setting be fine - after all, the majority of the picture hasn't altered. It does create a file size about 20% larger though?!?!

Your thoughts and help is greatly appreciated!

When you initially saved them as jpegs you immediately lost around 20% of the light values each scan had as a jpeg automatically edits the image based on the parameters that have been set and discards what it doesn't need. It would have been far better to scan them in at 600dpi, as that is about the maixmum most printers can achieve and saved them as TIFFs. Even most 20x16 prints are printed at about 300dpi so scanning above this is a waste of time because you're unlikely to ever need such a high resolution image. Unless of course you're going to have them printed on the side of a number of large buildings!

Once saved as Tiffs you can edit them without any fear of further loss and Photoshop will also keep a record of what editing you've done to them and saves this information with the file, hence the reason the file size expands.

Hope this helps.

[Garawa]

Many thanks for that. That would explain why, when saving as TIFFs I got such massive file sizes. Can I ask why those settings are available? My scanner can scan up to 16000 odd dpi. What on earth would those be used for?

If I had a professional reproduction at say 16x12, would 600dpi really look the same as 300?

It seems I need to go back and rescan which I think I will do with our favourite ones to re-create the masters. As I have scanned 200 odd pics already and many wont be enlarged (as we have our album already) I might leave many as is. Would I be right in saying that as long as they are set to the lowest compression on both scan and touch up, I would lose little? I have enlarged both considerably on screen and cannot see any difference but don't understand why the new pic is bigger!!!!

[ianpinion]

Some scanners aren't just aimed at the domestic market but for the professional market too, where the likes of advertisers, for instance, need super high resolution images for marketing billboards etc.

Have you checked the canvas size of the negatives you scanned, by that I mean what size print it would produce if you were to use every single pixel? I am sure you would find it was massive! Now when you shrink down the size of that canvas to a more manageable size a printer can only reduce each of those dots down to a specific size because of the limitations of the laws of physics, hence if you were to print this file at 300dpi, just like a jpeg discarding the information it didn't need, your printer software would do the same thing. The difference though is your eye wouldn't be able to see any difference on the final print. Now if you compare one of your scanned negatives saved as a Tiff against one saved as a jpeg, both scanned at 600dpi and you will see a diiference in the tonal values saved in each, because one will show as an accurate representation of your scanned negative, while the other will look like it has been adjusted. Which is precisely what has happened.

Now to answer your question as whether 600dpi would look the same as 300dpi depends on two critical elements. The first is the size of the print and the second is from what distance are you going to view the print. Well you've mentioned the size would be 16 x 12, which you could print sucessfully at about 250 - 280dpi and the image would be perfectly crisp as you gazed at the whole print from a comfortable viewing distance. However, if you were to scan an area of the image with a magnifying glass it may not look as good, but that's not how you're really going to look at it. Now if that image was printed at 600dpi it would look better under a close inspection, but from a distance our eyes wouldn't tell the difference.

So the dpi required is only relavant to the size of the canvas we are going to print it on. The larger the canvas, the greater the dpi has to be to achieve the required quality, but you don't have to go to extremes!

[Forseti]

Originally Posted by Garawa

My scanner can scan up to 16000 odd dpi.

dpi = dots per inch - a term often used incorrectly by scanner manufacturers (as well as many others, including photographers) as this term only applies to printers.

ppi = pixels per inch and refers to resolution. Say for example your camera is capable of producing images at a resolution of 5184 x 3456 pixels. If at the printing stage you decided to print at a resolution of 240 ppi (pixels per inch) then you can see that by dividing both these figures by 240 you would be producing a print of 21.6 inches x 14.4 inches (using exact figurers). Increasing the resolution to 300 ppi and repeating the division exercise would give you a print size of 17.28 inches x 11.52 inches - agin exact figures.

In short then, your scanner is capable of scanning up to a maximum resolution of 16000 ppi (pixels per inch) not dpi (dots per inch) but here the manufacturers are to blame for using incorrect terminology probably part historical prior to the invention of digital imaging and partly an us - them thing. Who knows.

Not directly related to your initial question I know, but from the above you can see why people generally post low resolution images to the web......72ppi, because at this resolution attempting to steal and print out an image at a reasonable resolution of 240ppi would give you a print size of..........well nothing.

[Garawa]

Fantastic resposes Ian and Forseti, they explained so much. Thank-you!!! I wish I had tried some scans and then asked before doing the blooming lot!!!

I thinks I will do the alterations to the OK pics and then re-scan the best ones to TIFF again in their own folder. At least I will be able to see what the picture looks like instead of holding them all up to the light and squinting! When Kodak stopped their wedding photography service and sent the negatives to us I am so glad they used 120 format, they scan a million times better than 35mm.

Thank-you once again.

[Forseti]

Originally Posted by Garawa

Fantastic resposes Ian and Forseti, they explained so much. Thank-you!!!

You're welcome.

[KeithT]

There is no harm in scanning at the high resolution, but if you scan film at too high res you start to scan grain which will appear like jpeg artefacts when you view at 100%. I scan all my negs and slides at 2400 ppi to ensure I don't lose detail, but pull back to 300 ppi as soon as the scan is in Photoshop and then save as a 16 bit TIFF. Ressolution for printing depends totally on the size print you want. 72 ppi is suitable enough for 6x4 and maybe 7x5 prints for instance, but not for anything larger as you will begin to see pixilation as you expand the image. 25O ppi would be fine for a 10x12 although I tend to use 300 ppi for everything, even if at times it is a bit of an overkill.