Photoshop shows how much memory an image takes up. This is not the same as hard disk space. I need this because a stock library has a criteria related to file size in memory. Affinity Photo also shows it. For example; on disk I have an image which is 20 Mb. The fly-out you get when you hover over an image in the film strip in Customise mode also shows 20 Mb. But, apparently, the file size in memory is 30.4 mb. (I don’t quite understand why it is larger but I would hazard a guess the memory version is decompressed).
Hi, I think you’re confusing megapixels (MP) with megabytes (MB). MP is a simple calculation: multiply the image width by its height and divide by a million. For your example above, it’s 30.4704 MP. File size in memory would be bigger, depending on the number of bits needed to render each pixel in its proper color. A 24-bit color image needs 3 bytes per pixel (8 bits = 1 byte for each channel - red, green, and blue). Even more memory might be used for metadata and other things stored in the image file. A megabyte is 1,048,576 bytes (1024 kilobytes x 1024 bytes per kilobyte).
@Egregius
Thanks. Yes - my post was hopelessly confused. I just copied what i saw in Affinity without paying attention. MP as you say. Thanks for the additional explanations.
However - my question is valid (not that you could be expected to know that from my mistake). This is what Alamy say: " What file size do I need to upload? A. We need a file size of over 17MB when uncompressed (this is likely to have a compressed JPEG size of 3-5MB). Opening a JPEG in an image program such as Adobe Photoshop will show you the uncompressed (open) file size.". I need this 17MB (bytes) figure.
A quick Internet search suggests that what I am looking for - the 17Mb - is not available in Affinity. However - it is in Photoshop. In Photoshop it appears in a little info bar at the bottom left. I no longer have a Photoshop subscription so I can’t see it. (Well, I removed PS from my computer in anticipation of the joyous day when my subscription does not renew).
I think DXO does not have this feature? If that’s correct I’ll make a feature request.
The size of this image is 6048x4024 pixels. Every pixel takes 3 Byte. So the size is 6048x4024x3=73011456 Byte. Divide this by 1024 and you get kB. Divide it again and you get MB. Result 69.629 MB or 69.63MB.
On window ALT + ENTER opens window property of file in focus.
And you get file size and file size on disc and several info related to the file too (just have to check different tabs.
TS is talking about jpg’s. They’re 8 bit.
Further the unit used in photography and computers are bytes.
Did you read the question and the link to Alamy?
Distinguish between a disk file and a memory file. The memory file contains only the image, the disk file contains the image in a certain format and the added data.
See my calculation in the other thread. Every pixel in memory takes 3 byte for the channels. So the size will be 17/3.
Assuming jpg and an equal bit depth in memory. For jpg that’s 8 bit.
Oh, sorry if I wrote b instead of B. In my langage this is b and o. So I sometime do mistakes when writing in english (caps are not relevant in my langage for this, only lower case is used).
I will correct my post above. (MB instead of Mb and kB instead of kb).
Don’t quibble. Your formula is ok for Jpg, mine is ok for any kind of image (any bit depht (8/16/32) and with alpha channel too - that photolab do not manage).
But ok, maybe I didn’t see that the question was about jpg only.
PS : to be precise not every kind of formats : Not exr which can contain any kind of channels, not tiff with several layers (they are more than images). But common images used with image processors.
You don’t answer the question TS wants an answer for. What is the memory size of an jpg image? In byte units.
Using a bit depth of 4 will still use 3 byte. A bit depth of 12 will use 6 byte. It’s all ways a multiple of 8. This doesn’t count for the RAW files, a RAW file with a bit depth of 12 does have another size as a RAW file with a bit depth of 14.
From my post 6
In your formula every pixel takes 24 bytes or grows with a factor of 24.
isn’t a jpg image compressed ???
So is it about the size of the image when used by photolab for processing (which is NOT a jpeg image), or is it the size of the jpg ?
