jpeg picture quality in mobile phones

[tethered goat]

In some of the better quality camera apps there is now a choice of "jpeg quality", i have a choice in one app from 55% up to 100% and others 90% up to 100% in another. I'm unclear why i have a choice to shoot at 55% quality, but that is not the purpose of this post.The same as choosing "Fine Quality" on a regular camera i would just choose 100% quality in a mobile phone BUT i keep being advised that 85% or even 95% are better choices, does anyone understand why this might be ? I don't think it is anything to do with oversharpening as i have a separate choice on how much i want my pictures sharpened [or not] I am posting this in the Photography section but dont know if it would be better understood in the mobile phone section. Phone cameras are getting better all the time although they are still struggling in low light and i'm sure the differences i am talking about may be negligible but i just like to understand the tools i am using.So the question again is why is using less than 100% quality a better choice than 100%.

ps i googled this but could not find any info.

[Tywais]

The difference of course is in the size of the final file and quality required. If you are posting the images to a website then the 55%+ will be suitable as screen resolution doesn't need more and uses less bandwidth for viewers. If for printing then 100% is what you will want to reduce compression artifacts as much as possible. So it all depends on what you will be doing with the images.

[tethered goat]

Thank you Tywais, i was hoping you would have a thought on it, but why is this different from "picture size" The first choice i have in settings is "picture size", aspect ratio and megapixels, so i can choose [4.3] @ 13.0 megapixels or [16.9] @2.1 megapixels or whatever size i want that is suitable for what i want to do with the picture, so still unclear about where jpeg quality fits into this as it still means i can have if i choose 100%jpeg quality shot at 2.1 megapixels which is a small file size.?????? I'm definitely out of my comfort zone here.

[tethered goat]

just found this site which answers my question in detail http://www.hongkiat.com/blog/jpeg-optimization-guide/ thank you for your help Tywais

[Tywais]

Thank you Tywais, i was hoping you would have a thought on it, but why is this different from "picture size" The first choice i have in settings is "picture size", aspect ratio and megapixels, so i can choose [4.3] @ 13.0 megapixels or [16.9] @2.1 megapixels or whatever size i want that is suitable for what i want to do with the picture, so still unclear about where jpeg quality fits into this as it still means i can have if i choose 100%jpeg quality shot at 2.1 megapixels which is a small file size.?????? I'm definitely out of my comfort zone here.

Picture size is related to the amount of the sensor that the camera will use when taking a photo. For your above example, native size of 4:3 13Mp would use all the pixels of the sensor. 16:9 @2.1 would only use the pixels necessary to satisfy the 16:9 and as such fewer pixels being applied to the image the smaller the file size. You'll see at 16:9 there black bars at the top and bottom which are not saved as part of the image.