An interactive way to do this is File - Save for Web. There you adjust the quality and under the preview you get a readout of the File size.
You do not seem to understand the Jpeg file formats uses data compression and that the compressed data size depends on the compression method user and the actual data. Data requires to record a field grass in much more complex and larger the the data requires to record the details in a blank white wall or a blue sky. A 20 Mega Pixel image saved as jpeg file may be smaller then 100KB or larger then 7MB. Jpeg file can record Pixel data and also Vector Path, have metadata and Profile data. Does not support Layers and layer transparency. What is recorded in Jpeg file vary.
Thanks Gener7 for the tip. I will give this a try. I always equated Save for Web differently and never gave it much thought.
Thanks JJ. I'm pretty aware of the concept of JPEG as a compressed format. My issue really lies in the fact that two PSD projects, which contained the same subject and virtually identical layers output at completely different MB when compressed to JPEG. But, I was not as aware of how complex a picture is in it's final output which you cleared up. As I mentioned, the issues were with almost identical files with the second having a bit more noise reduction and less sharpening than the previous. So with that in mind, I had less to save in regards to picture information. All helpful here.
almost identical files with the second having a bit more noise reduction and less sharpening than the previous. So with that in mind, I had less to save in regards to picture information.
Yes, a drop from 20 to 10 MB is fully expected there, and it can often be even more. High frequency detail is precisely what affects jpeg size the most.
I need to have files saved as JPEG with a minimum of 17mb.
...and that is of course a red herring if ever I saw one, as you're probably well aware of by now. Jpeg file size says precisely nothing about the quality of the image.
Its about content detail Noise lots of detail no noise no detail. Blades of grass lots of them blue sky blue no detail large blue area. It requires lots of data to record high detail. Large area with little to no detail can be recorded with small amount of data.. Noise is high detail for sure.
If compression is being used when you save the PSD files they should vary some in size however they should be larger in size the the jpegs. Fort different compression is used and layers saved are not composited into a single image layers like in jpeg format. Also alpha channels and layer mask are save is PSD files. They are not saved in Jpeg . Vector layer mask and vector Paths are saved in Psd only only vector path are saved in Jpeg Vector layers mask are not. It about content and how much of it there is and the compression used.
You wrote used Jpeg Quality 12. That only effect jpeg compression. If you use 10 the jpeg files you save will be much smaller and you will not see the difference in image's quality on first generation saved jpeg files.
2 things stand out :.. I need to have files saved as JPEG with a minimum of 17mb.
Who is demanding this minimum file size?
Can you provide complete details?
It sounds like you sending files out to be printed.
As "21 TwentyOne" mentioned: Jpeg file size says precisely nothing about the quality of the image.
Are you also saving your projects as .PSD in addition to .JPG?
JPG files are flattened and you lose the ability to edit the files very much since it no longer has any layers.
JPG is also a lossy format which means it reduces image quality every time it is saved. That is how you can get smaller files sizes, but at the price of quality.
Bo - I am attempting to send my photos into Alamy.com. Their requirements are for JPEG's at 17mb or higher. The files are ultimately set for sale.
The quality of the image seems great to me but if requirements are for 17mb, even if the 10mb looks great, I'm not sure it will be acceptable. I do, however, have a question about quality over file size into Alamy.com in hopes that it can still be acceptable.
All is saved in PSD form. I have a very good understanding about JPG as a lossy format and it's not being editable once it's created. My issue, as I had stated, was about the differences in file sizes of the same picture but of slightly different edits. It seems like, JJ was able to rectify my understanding of this size issue.
Everyone has been very helpful. It seems that if I am to have this one photo accepted, sans the noise and sharpness as recommended by Alamy, I will need ensure they can accept the lower MB but still a high quality JPG.
Robert, You might want to look a bit closer at the Alamy.com website.
They are asking for uncompressed file sizes of more than 17 MB.
In fact if you hover your cursor over this requirement on their website, a tip pops up that says:
"When you open a JPEG in picture editing software (i.e. Photoshop). it is uncompressed."
So they aren't asking for a file size >17MB in the Mac Finder or Windows Explorer, but rather its uncompressed size in Photoshop.
For example, the image below is only 6 MB in the Mac Finder, but uncompressed in Photoshop is it over 190MB.
At the bottom of your image frame in PS there is a field that can display various parameters of your image by clicking on the arrow to the right.
Click this arrow and select File Size.
I'm sure your file size is adequate for them.
However, I would pay attention to the list of "We reject images for . . . requirements.
Bo - Thank you again. I can safely say I was unaware of the differences in file size in say, Windows Explorer and in Photoshop. I just placed my JPEG, which is approx 10mb into Photoshop and checked the image size and it's 68.7mb.
You definitely learn something new everyday. I assumed the output size was the be-all, end-all to my issue. And I definitely misunderstood Alamy's requirements.
Thank you for helping me clarify this and also to everyone here on this board for giving me a bit more understanding to this issue.
Jpeg supports 8 bit color depth only. So if you has an 6 Mega Pixel Camera an uncropped RGB 8 bit color depth image would be 18 MB, made or 8 bit red, 8 bit green and 8 bit blue for each pixel. This will be larger then the files size from your camera for Cameras use data compression. Additionality RAW files are not strictly a RGB images. There is a scaled down Jpeg preview however the RAW data is not RGB there is one value for each pixel how many bits depends on the camera's sensor. 10, 12 and 14 bits are common. On top of that data compression is use when writing out the data. My 8MP camera Raw files normally weigh in at 7 to 10 MB its uncompressed RGB 8 Bit Image would be 24 MB.