A digital imaging question...

[Route 66]

First of all, I hope I'm using the correct terminology here...

I know that by multiplying the pixel height x the pixel width will give you the total megapixel count of the image. Example: 1600 x 1200 = 1920000 or 2 megapixels.

Is this also the the megabyte count?

In other words, how do you convert megapixels into megabytes to determine the size of the image?

Thanks

[Tools]

Pixels and Bytes do not relate/convert directly.

You need to know how many bytes per pixel your hardware/format architecture produces.. and it will change if you are using 8 bit or 16 bit, or down processing for the web, or up processing for a large print.........

Converting pixels to bytes requires calculating the number of pixels multiplied by the bytes per pixel

[Route 66]

Originally Posted by Tools

Pixels and Bytes do not relate/convert directly.

You need to know how many bytes per pixel your hardware/format architecture produces.. and it will change if you are using 8 bit or 16 bit, or down processing for the web, or up processing for a large print.........

Converting pixels to bytes requires calculating the number of pixels multiplied by the bytes per pixel

WOW! Thanks Larry, but I'm afraid you answer is over my head.

If I take a picture with my digital camera, how can I calculate its file size? can you give me an example of how this would be done?

[Tools]

Originally Posted by Stevarn

WOW! Thanks Larry, but I'm afraid you answer is over my head.

If I take a picture with my digital camera, how can I calculate its file size? can you give me an example of how this would be done?

I wish the answer was a simple one...

Let's just generalize and say that the typical consumer camera will generate 3 bytes per pixel... one for each basic color... high end cameras can also add data for color/contrast/ etc..

But... If you use jpeg as your file default (instead of RAW), your files are compressed downwards and many cameras have several different "levels" of jpeg compression..

If you do not know, and your camera just does it all for you, then probably using 2 bytes per pixel will get you in the ballpark.. If it does not save at a high quality level, the file size will be a lot less..

[rfknauss]

Steve, the easiest thing to do is use a software product like PhotoShop and just reduce the DPI to 72. That is what computers use to view a pic. The software will tell you what the new file size is in MB or KB.

[Route 66]

Thank You Richard, but I don't have Photoshop and I'm not about to spend $700 on a program that has a very steep learning curve.

I'd just like to know how to calculate the file size of my images...for free

[Tools]

Originally Posted by Stevarn

Thank You Richard, but I don't have Photoshop and I'm not about to spend $700 on a program that has a very steep learning curve.

I'd just like to know how to calculate the file size of my images...for free

Oh.............. free....

OK then.... Insert your flash card into your camera.. Look and see how many images it says that you can take..

Divide the size or your card (say 4 gigabyte, etc.) by the number of images you can take.. This will give you the approximate size of each expected file..

[Jocke]

The image size is not just about compression, it affects the number of colors and details too. As there is no real formulas are available.

[Route 66]

Originally Posted by Tools

Oh.............. free....

OK then.... Insert your flash card into your camera.. Look and see how many images it says that you can take..

Divide the size or your card (say 4 gigabyte, etc.) by the number of images you can take.. This will give you the approximate size of each expected file..

Thanks Larry, I sure didn't realize that there wasn't just some simple formula involved. Your method gives me something to go by.

Originally Posted by Jocke

The image size is not just about compression, it affects the number of colors and details too. As there is no real formulas are available.

...and Thanks Jocke, I had no idea that what I was asking was so involved!

Many times on websites, if you want to post an image, they tell you it can't exceed say...50MB. How the heck are we supposed to know if ours is too large, if there's no simple way to calculate it?

[Pix]

Here are some basics...8x12in @ 72dpi = 576w x 864h pixels
4x6in @72dpi = 288w x 432h pixels

[Tools]

the only way to know the actual file size is to click on it's properties..

Almost all images have a slightly different file size....... If you want to reduce it's size (file wise, not image size), you need to resave it at a lesser (more compressed) size..

Most software today has a "web size" feature that reduces image files by 40 or 60 percent........ or more...

[Route 66]

Originally Posted by Tools

the only way to know the actual file size is to click on it's properties..

Almost all images have a slightly different file size....... If you want to reduce it's size (file wise, not image size), you need to resave it at a lesser (more compressed) size..

Most software today has a "web size" feature that reduces image files by 40 or 60 percent........ or more...

Awe, to hell with it!!

I'm going back to film!!

I appreciate all your help Larry!

[TheDude]

If you're talking RAW capture, in the old days this was predictable. Nowadays, each camera maker uses proprietary lossless compression on RAW images. Depending on the image captured, the compression will be more efficient or less efficient. If you're shooting RAW on a modern camera, the "shots left" readout is a guess and could be off by one or two.

As evidence, the RAW files on my 5D are all slightly different sizes even though they are the same pixel dimensions and coming off 12 bit AD converters.

Others have said, the capture depends on the AD converter in the cam. Most cams are 12 bit AD. Some newer high-end models are 14 bit. Uncompressed, doing the math would give you the actual size of the image in RAW.

When it gets converted to JPEG, this is usually 8 bit, the 12 or 14 bits of information are crammed into the 8 bit space and are compressed using either an in-camera algorithm (if the camera is saving a JPEG) or using a JPEG compression algorithm that will likely have user defined settings in a software application.

Lots of folks will convert a 12 or 14 bit RAW file to a 16 bit TIFF file to perform editing and printing. This will be larger, since more bits per pixel of information are being saved. Data from the 12 or 14 bit RAW file are extrapolated to fill the 16 bit space. TIFF compression is predictable.

[TheDude]

Originally Posted by Stevarn

Awe, to hell with it!!

I'm going back to film!!

I appreciate all your help Larry!

Film scans are predictable - they are TIFFs natively and you can calculate the size based on channel info and bit depth.

[Route 66]

Originally Posted by TheDude

Film scans are predictable - they are TIFFs natively and you can calculate the size based on channel info and bit depth.

Sorry Dude, but now we're on to "channel info and bit depth" and it's still beyond my ability to understand.

[TheDude]

Originally Posted by Stevarn

Sorry Dude, but now we're on to "channel info and bit depth" and it's still beyond my ability to understand.

Some scanners also capture an IR channel so that you can perform dust/scratch removal later. This is in addition to the RGB. This is known as RGBI. 64bit in this mode. Biiiig files.