[mouldy101]

Hi all,

Not sure if this is the correct forum to ask this question, but here goes. I use PS CS2 to convert my RAWs to JPEGs and I am very new at doing it... I am having great fun actually converting them, but get a bit lost when saving them. What settings are best to ensure good quality JPEGs??? What would the benefits of saving as TIFF's??

If someone could talk me through it (slowly ) I would appreciate it

Thanks in advance!!!

Matt

[Gary Bagshawe]

Jpegs are great for saving for web and smallish reprints but if you are going to sell your work on image libraries etc then tiffs give you much better quality. The downside is that tiffs are big files and so take up much more space on your hard drive.
Tiffs retain much more detail than jpegs and really it depends on what you are going to produce as an end result.
I WAS a big jpeg user as most of my work would not require huge files for reprinting but I have found over the last 12 months that I am even shooting photographs for newspapers in raw forrmat then saving as a tiff and jpeg and e-mailing the jpegs to the papers, time permitting.
Hope that helps a bit.

[mouldy101]

Cheers Gary that does throw a bit more light on the subject thanks

[Rob Barron]

Mouldy, let me give you a brief explanation of different file types as that might help you:

Raw files:

(.crw or cr2 on Canon, .nef on Nikon etc) are files which are untouched by processing. They are big file sizes as no compression at all is applied to them (for all practical purposes anyway!)

.jpg files:

(usually refereed to as jpegs) are compressed files. The computer looks at areas of colour that are the same and uses algorithms to store the colour once and applies it to all locations where that colour exists rather than storing the location of every pixel in every colour. This means it can be stored in a much smaller memory space but fine detail is often lost. Also, every time you save a .jpg it is compressed again so if you keep opening and saving before closing, the quality will deteriorate each time until it becomes so awful it is no use anymore. So if you have not worked on a jog, you have only viewed it, choose NOT to save when closing as that will avoid compressing again.

jpegs are the ones to always use for websites as you show them at low resolution without them looking terrible and without them taking forever to download/open on screen.

.tif files:

Tiff files do use a type of compression but this is known as 'lossless' because it stores much more information and does not take out the minute detail. That means these pictures make superb prints but are much bigger than jpegs so are no good for showing on web sites.

Top quality jpgs usually start out almost as good as tiff files but because of the recompression problem, they will not look good after many saves whereas tiffs will. So, when working on a photo, keep it as a .tif file until you are certain you have done all the post processing you want to. Then save a copy as a jpeg and use that for web or lower quality printing purposes. I stick my tiffs over onto my external hard drive where they are backed up to avoid wasting space on my main computer hard drives.

Hope that gives you a bit of help.

Cheers,
Rob

[Soupdragon]

Pretty much what everyone else said with the exception of .NEF files which are compressed in camera on the entry level models.

[mouldy101]

Thanks people,

All useful info. thankyou. I have only been using the raw format for a few weeks and have noticed that after using the RAW converter on PS CS2 and saving the image, it is still massive (ie 8-10 Mb on one occasion 14Mb!!!!). Is this usual??? I am using a canon 350d and CS2 as I say. Am I doing sometging wrong or is this normal. Any advice gratefully received....

Matt

[Soupdragon]

Sounds about right to me!
I normally convert my files to TIFF using Canons DPP which makes files of about 45mb.
I do this for archival purposes though.
If you want smaller images, adjust the images then crop what you don't want (if applicable) then do a file save as, save them as .JPEG at this point CS will ask how much compression you want to apply.
Move the little slider and look at the bottom of the dialogue box to see what the final file size will be.
This only works on 8 bit images and not 16 so you need to make sure you change this before attempting to save as.

[mouldy101]

Cheers Soupdragon. It just seemed large to me!!! I didnt know if I was doing something wrong......

[Rob Barron]

Originally Posted by Soupdragon

Pretty much what everyone else said with the exception of .NEF files which are compressed in camera on the entry level models.

That was why I added 'for all practical purposes' when I said no compression is applied! I know Nikon does compress very slightly for some reason (can't see how they are still RAW files but there we go) with their lower level cameras but it is so small as to be irrelevant in this particular discussion.

Why does Nikon compress raw files though? Does anyone know? How can a compressed file be the raw pixels as taken by the sensor? I guess it is just the way the image is actually stored but no idea. Not that I use Nikon anyway, just interested to know.

Cheers,
Rob

[Soupdragon]

I think they do it to speed up write to the memory cards.

[mouldy101]

When converting my RAW files I always save them at the highest quality JPEG... With the 8Mp on my 350D what size print could I achieve. The largest I ever print is 10x8/A4 is it overkill to save them at such a high quality??

[Sonsey]

Originally Posted by mouldy101

When converting my RAW files I always save them at the highest quality JPEG... With the 8Mp on my 350D what size print could I achieve. The largest I ever print is 10x8/A4 is it overkill to save them at such a high quality??

I've had 30x20in prints done at Photobox with excellent results, even with some cropped shots

[Soupdragon]

The industry standard for photo quality printing is 300dpi.
I think for the purposes of home printing 200dpi is about as much as you need (someone is going to debate that)
So, by my logic, if you want to make a 10" X 8" print you need an image size of 2000 X 1600 pixels at 200dpi.
Obviously to print 10 X 8 at 300dpi without interpolation you need an image size of 3000 X 2400 pixels, well within the limits of your 350D sensor.
That said, JPEG compression is a process that I do not understand and must discard colour depth information somewhere along the line.

[Rob Barron]

The most important factor to remeber about jpeg is what I mentioned in the files thing above: each and every time you save a jpg it is compressed again. So although when you first do it, it looks great, when you have done that a few times, it will degrade.

If you want to work out the size you can print something out, just multiply the size in inches by 300. So a 12" x 8" at 300dpi will be 3600 pixels by 2400 pixels. That would need an 8.6MP sensor.

However, although 300dpi is considered the top quality figure, above which it is said the human eye can't see any difference, you really won't notice any great difference if you go down as low as 200 dpi and even as low as 180dpi for a large print that is naturally viewed from a distance.

That means you can print a 12" x 8" at 2400 pixels by 1600 pixels, that is obtainable from a camera with less than 4 MP so you can easily manage that on a 350D picture. An A3 print at 180dpi would be easily possible without interpolation with a 6.3MP sensor (Canon 10D for example).

Interpolation up to a 30" x 20" at 200dpi would be absolutely fine and you'd be amazed at the quality of the results so you have plenty of scope to get radical if you really want to :o)

Cheers,
Rob