Images Sizes (Compression Rate in Canon)

[elbaduj]

Hi,

I have a question regarding the size of the pictures. Normally I use a compact camera. I had a Canon Ixus 85 (10 Mp) that produced images around 4.5-6 MB with the superfine compression (maximum quality). Now I have bought a new camera, Canon IXUS 300 (10 Mp also) that produces 1.5-3 MB images (max quality also), less that half than the old one.

The best compression option is "good", there is no superfine. Does this mean that the quality of the picture is worse in the new camera? As the size of the image is the same in both cameras, is the loss of quality in the depth of the colours?

The only difference I see when I open the pictures in Photoshop is the bits per pixel, the 300 obtains 3.0 and the 85 gets 5.0 but in the CiC tutorial says that the normail bpp is 8 or more always so... I do not understand anything.

In summary, apart from other features, the new camera stores the pics with less quality than the old one, how can that be possible? or why is there such a big difference in the size of the pictures? Will I notice anything if I print a pic out.

Thanks for you help, Elbaduj

[Colin Southern]

Hi Jose,

I had a bit of a read up on the internet for you -- I found 1 reference to "The Canon IXUS 300 HS has 2 different image quality settings available, with Fine being the highest quality option."

http://www.photographyblog.com/revie...image_quality/

Is this what you've found?

[elbaduj]

Hi Colin,

This is what I do not understand. The highest quality option produces 2.5 Mp images, and in my old Ixus 85 the with the highest quality you get 4.5-5 Mp images. Have the Ixus 300 pics worse quality than the 85 or have both same quality? If so, how can that be possible if the size is smaller (more compressed). Sure there is a good reason that explains this but "my feeling" is that I will get poorer quality when it comes to print pics out.

Thanks for your time, Jose

[Colin Southern]

Hi Colin,

This is what I do not understand. The highest quality option produces 2.5 Mp images, and in my old Ixus 85 the with the highest quality you get 4.5-5 Mp images. Have the Ixus 300 pics worse quality than the 85 or have both same quality? If so, how can that be possible if the size is smaller (more compressed). Sure there is a good reason that explains this but "my feeling" is that I will get poorer quality when it comes to print pics out.

Thanks for your time, Jose

Hi Jose,

I think the only way to tell for sure it to just print some and see. I doubt you'd be able to tell the difference as @ 10MP you'll be getting a LOT more information than the eye (or printer) is capable of resolving, unless you doing pretty big prints (ie perhaps 8" x 4" or bigger).

They could have a more lossy compression in the newer camera - but keep in mind that there's a big difference between what is less quality "in theory" and what is actually visually obvious (we strike this in Photoshop all the time - using a quality setting of 10 instead of 12 could easily halve the size of the file, but you won't be able to see any difference).

[Sunray]

The Canon IXUS 300 has a special "Low Light Mode" and a "High Speed Mode". In low light mode four pixels are joined together to increase light sensitivity. In high speed mode a smaller amount of data is stored to increase the maximum picture-shooting rate per second. When using one of these modes the 10MP sensor produces "only" 2.5MP pictures.
Disable these modes and you will get full 10MP sized pictures out of your camera.

Robert

[elbaduj]

Thanks for the answers. My concern was more about how it is possible to reduce the size of a pic without affecting "visual" or "printed" quality. I hardly use Photoshop so I did not know what Colin said about sizes and perceived quality.

Thanks also Robert, I have seen the modes you mention in my camera. Now just keep on clicking to improve my skills

Cheers, Jose

[Colin Southern]

My concern was more about how it is possible to reduce the size of a pic without affecting "visual" or "printed" quality.

Hi Jose,

Have a read up on how JPEG compression works. Basically, our eyes aren't particularly sensitive to certain changes - so JPEG compression will normalise the levels that we can't differentiate, which makes the image more compressable.

I'm not saying that this is the answer to your question, but perhaps one possibility. It could be that the original camera didn't compres the images enough? Who knows - I'd let "the proof of the pudding be in the eating" though as we say -- if the printed / displayed images look OK then I wouldn't worry about it