"Controlling" file size (1 Viewer)

This seems like the least wrong forum for a question that I'm sure I've asked before, but can't seem to find.

Is there any way to "control" the file size of my photos? If it makes a difference I use an Oly C-750 UZ and I save the files as .jpg format.

I guess that the size of a given photo depends upon the amount of detail.

However, looking at Paul Hackett's Purple Sandpiper, this is a fabulous pic with loads of detail, yet the file size is about 102K.

When I take pictures, I have to reduce them, sometimes as low as 500 x 300 to get the filesize small enough.

Clearly I'm missing a trick somewhere!

Any suggestions?

Birdman

Download Easy thumbnails from http://www.fookes.com/ezthumbs/index.php?2.6 one of the options when saving is JPG quality.
Most packages have something similar, but this is a simple good package to use.

The same applies if you have Photoshop. Use the "Save for Web" option and then adjust the quality until you get the file size you require.

Yes, it's all about jpeg compression rather than the physical dimensions of an image (though reducing it has to be done as well for the web). On any Photoshop version, using the 'save as' function will eventually bring up a jpeg compression slider control, modern version have the more luxurious 'save for web' function that gives you an actual view of the effects of jpeg compression.

Some photos are a nightmare to reduce in size without losing quality in the subject .. anything with gravel or grass means far more detail (especially if sharpened!).

I have found that different photo programs cope with jpeg compression better than others. Some yield very grainy results and yet others very good ones.

Personally I like Paint Shop Pro best of all and Photoshop is very good and easy to use too - you don't need the current super-dooper version any version will do. Thumbsplus I like for a variety of features but the jpeg compression is poor. Neatimage is an excellent and free to download program that whilst 'smoothing' the noise also reduces the file sizes very effectively.

Most cameras give you the option of compression at the time of taking a photo so it can be controlled that way too. Personally I don't use the higher compresions in-camera as obviously you then have smaller file sizes to crop an image.

Thanks everyone...

Just a general question in relation to this, is it always A Good Thing to take your photo in the largest dimension, highest quality size possible (there are many options on the Oly, so I suspect there are on all others) and then reduce it from there?

It seems to make sense.

I use the CP4500 and always use the highest quality JPEG size (not TIFF) and then reduce it as necesssary. Basically because you can't sucessfully (IMO) take a small image and enlarge it.

Absolutely Birdman....Always get as much detail as you can in the original capture....then downsize from there....I shoot in RAW and get file sizes of 6MB....then I develop the image in Capture One which produces an 18MB Tiff file...Then I downsize my files to put into the Forum Gallery in Q-Image....which gives me roughly a 50KB file that is quite sharp when viewed on a monitor.
Muskrat

An interesting and toally unexpected sideline to this, that I wonder if anyone can explain...

At the minute, I use the Camedia softeware that comes with the camera to resize my pictures. I'm taking pitcures at 2288 x 1715 HQ jpeg at the moment.

If I resize this to 800 x 600 and "Save as", the file size varies between 200 and 300 K, give or take.

By accident, I "Save"-d last night, and this file size was reduced by about half. Further deliberate "Save"-ing produced file sizes between about 80 and 180 K.

Erm... why?!?!?

You're 'chucking out' info every time you save as a jpeg file so you're effectively reducing something that has already been reduced.

You're also gradually reducing the quality of the detail each time - hence the smaller file size - so it's not recommended to keep 'saving' jpegs. If you want to try something different on a photo go back to the original file and work again from a copy of that, do all you want, and only save as a jpeg once you've done everything you want. If you can't do everthing all in one go then saving it as an intermediate tiff or photoshop psd file will retain all the details, but at a larger file-size.

Aaahhh! Thanks Adey... that seems to make sense.

I have to say, I didn't seem to lose anything in terms of picture quality, but I guess that might be down to monitor resolution perhaps?

Either way, I guess, once the detail has gone, you can't get it back!

dimensions are the critical thing!

Birdman,
I disagree with what some have said here that it is the amount of jpg compression that is critical, not the dimensions of the file. Assuming that you do not use too much compression, absolutely the most important aspect of an image file is its dimensions (width and height). The dimensions you make an image depend on what you want to use it for.

In your original posting you said, "When I take pictures, I have to reduce them, sometimes as low as 500 x 300 to get the filesize small enough." Small enough for what? What you should be concerned with is the dimensions. If you intend your image to be displayed on the internet, your main issue is how it will look on the screen. This is purely a function of the screen resolution that people use. Some use 640x480, some use 800x600, some use 1024x768, etc. So, if you post a picture that is say 800x600, it will more than fill the screen of a viewer whose resolution is 640x480, and even someone using 800x600 will not see the whole picture because the browser window takes up screen room (button bars, status lines, etc). As a general rule, design for 800x600 (few use 640x480 anymore). Thus, your images should probably be about 500x375, again to allow room for the browser area.

None of this has anything to do with jpg compression or file size (in K). After you have decided on the proper dimensions of the file, THEN you tweak the jpg compression, trying to get the best compromise between quality and file size, so the file will download fast to the viewer's browser. This is what Paint Sho Pro's File Export->JPG Optimizer is for. It allows you to see what kind of jpg "artifacts" you will pick up in the image at various levels of compression.

If you are going to be printing an image, you almost never want to lower the dimensions of the image. In this case, you use the Resize function with the "Actual Print Size" option chosen and manipulate the Resolution field - the "dots per inch (DPI) - to give you the print size you want (don't go much below 200!).

By the way, you mention that you use the HQ setting of you C-750. I agree with this. I have a C-730 and did some testing to see the difference between HQ and SHQ (which produces much larger filesizes because it uses less jpg compression). I couldn't see any difference, even blowing the image up on the screen enough to view individual pixels.

Thanks RAH,

You make a good point about dimensions, that I shall bear in mind. You probably guessed I was thinking screen-size, but in my mind I was expecting pix to default to physical screen width.

Thanks to eveyrone else who has contributed here with some excellent advice.

Oh, I have so much to learn!

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