Question re: file size and RAW

golfman

Hi guys,

Just started experimenting with RAW and I'm loving it! Just one question. The file sizes are pretty big when converted (8MP) and most of my images will be used for Daft.ie and property brochures.

Is resizing before converting the best option here? What size would be best for Daft/Myhome and property brochures?

Cheers

NothingMan

I would do all the processing you want with the original RAW file. Then save a copy as a small jpeg. Keeping the original RAW file for future work.

If you resize before converting then and you realise you left something out or could have done something better then you've nothing to go back to so keep the original RAW file stored.

ant_moore123

Are you using photoshop to save the JPG?

If so just save it in a lower quality and that'll make the file size smaller

Thats how i do it anyway

.Longshanks.

Original 10-12MB RAW file --> photoshop --> cropped to suit @ approx 1200px wide @ 200dpi --> saved to jpeg = about 400kb

stcstc

golfman

you are asking for 2 different things

1, for the websites - commonly 800 - 1000 pixels on the long side

2. brochures, these should use the higher res image

if your using photoshop, you could actually setup an action to save both the low res and high res jpgs (in different places too) for each image

Cameraman

For the screen (web) version, you can use Photoshop "save for web and devices". You should be able to use quality level 60 with no noticeable difference.

golfman

Thanks for the replies guys. I'm using the "Digital Photo Professional" from Canon that comes with the camera. It pretty much gives me 2 options when "converting and saving".

1) Change the image quality
2) Resize.

I want to keep the quality but have a smaller file size. I was assuming from that, that number 2 is the best option for me where I can choose the number of pixels each way.

When I mentioned property brochures, I didn't mean any fancy glossy ones (well not yet anyway), I mean those ****ty A4 sheets they give you when you go to a viewing.

CabanSail

The Image Size and Quality will both have an effect on file size.

Image Size sets how many actual pixels will be included. A screen can show a lot fewer pixels than a Printer can, so if the file is for the web then size it accordingly. If you look in the Random Photo thread here, then the photo's there are generally 800 pixels on the long side.

Quality determines how much the file is compressed. JPEG is a "lossy" compression format, so you loose data but it is very effective at making files sizes smaller. I will not go into how it's done but you can get away with a certain amount before it becomes obvious. When over done the photo will become pixelated and have a blocky look to it. For the screen you will can probably get away with about 60-70% without seeing too much effect on the actual photo.

As suggested above I would make two versions, one for print & one for screen. For printing, you want to work out how large the physical print will be & allow enough resolution for that. Steve has some information about this here.

JuliePhotoArt

I agree with CabanSail.
Really both resize and convert reduce image quality so don't be confused by wording here.

hbr

golfman wrote: »

Is resizing before converting the best option here? What size would be best for Daft/Myhome and property brochures?

Cheers

You can't reduce the file size without throwing away information. If you
use a file format that uses non-lossy compression like TIFF, PNG, ZIP etc..
only redundant information is thrown away so that the full image quality
is restored when the file is uncompressed. Lossy formats like JPEG
trade off a degradation in image quality for a big reduction in file size.

There isn't much redundant information in Canon's CR2 format, so the
only way to reduce file size by more than a few percent is to re-scale
the image or use lossy compression.

This is a Raw file from my Canon 500D

19MB IMG_6471.CR2 Raw file from camera
18MB IMG_6471.zip Compressed with zip
18MB IMG_6471.gz Compressed with gzip
18MB IMG_6471.bz2 Compressed with bzip2
16MB IMG_6471.tiff TIFF file (Gimp with LZW compression)
14MB IMG_6471.png PNG file (Gimp with max compression)
1.8MB IMG_6471.jpg JPEG file (Gimp at quality = 92)
1.2MB IMG_6471.jpg JPEG file (Gimp at quality = 70)
73kB IMG_6471.jpg JPEG re-scaled to 1200x800 quality=60

If you want to keep a full quality image for your archives, use one
of the non-lossy formats like raw or TIFF. Use full size and high quality
TIFF for printing, brochures etc. Scale down to a suitable size and
use JPEG at a medium quality setting for the web and e-mail.