What is more important for Image Quality? Pixels or Compression?

[Gusnyc]

Hi Everybody!

I have a question about image quality.What is more important to achieve better image quality, but keeping a reasonably compact image size per picture? Pixel count or compression level?

Let me clarify that I am not yet interested in RAW images because I want to practice with smaller files and shorter process time in Aperture. I am not doing professional work with my E-PL1, so JPGs are enough for the moment.

Like in any other camera, I can adjust the size of the pictures (in this case 3 different sizes for each Small, Medium or Large) and also I can adjust the level of compression.

I really don't want to have enormous files because I am not thinking about publishing or using my images for any professional work. If that would be the case, I would learn how to deal with RAW. My HD space is limited and I don't want to deal with external hard drives for my pictures.

Please let me know what do you think is more important to retain the best quality and a small-ish file size. Pixel Count or less JPG compression?

Thanks for your answers!

Gus

 

[Brian Mosley]

Hi Gus,

I'd look for extra storage space in the form of a couple of cheap USB drives (2 backups)... in the meantime, pixel count is probably more important than JPG compression.

Cheers

Brian

 

[Amin Sabet]

Gus, I noticed you have a Flickr Pro account, which is virtually unlimited cloud storage, so unless you have a slow internet connection, I think one good solution would be to shoot full-res with the least compression and upload it all to Flickr. If you only want some of your images to be visible on Flickr, set the rest to private. Meanwhile, only keep a select subset of your images on your hard drive.

 

[Gusnyc]

Hi Amin,

Thanks for your suggestion. For me it is more important to take all of my pictures wherever I go (within my Laptop and maybe my future iPad) than achieving the absolutely maximum quality. Large file sizes will compromise the process time with Aperture, opening the files, etc. That's why I want to achieve a balance between image size and quality. Even if that wouldn't be the case, maybe I the correct way to ask the question would be "What is more important to preserve image quality at the Mb? Pixel count or JPG compression"?

Gus

 

[Amin Sabet]

My personal preference would be reduced pixel size and less compression, but I don't think there is a correct answer.

 

[Brian Mosley]

It's an interesting question really... and we have two opinions in two posters... so I suppose a good test is needed.

Cheers

Brian

 

[Amin Sabet]

Less pixels would have a greater effect on overall detail, but I'm thinking that more compression would have a greater effect on color, tonal transitions, and shadow detail. I don't have an E-PL1 to know how compression affects outcomes with that camera, but I know that when I slide the JPEG quality slider in Photoshop, shadow quality goes out the window fast, and color transitions aren't far behind.

 

[kevinparis]

if you are using aperture then i would look into using 'referenced' files.

Shoot in high res jpeg or raw, but store the files on an external disk not in the Aperture Library... which is the default. Aperture will create a jpeg preview - you can set the size of this in preferences. The Jpeg preview lives in your Aperture library and is with you even when the drive with the master files is unplugged. You cant make adjustments to these previews when the master file is offline. but you can view them

it is the best of both worlds... you have a best resolution image safely backed up on another drive, and an image as good as your screen resolution on your computer where ever you go

K

 

[goldenlight]

Gus, let me put it to you that one day you grab a once in a lifetime shot - and it's low pixel count and/or high compression. You might regret that!

In your situation what I would do is shoot max resolution, highest quality JPEGs in camera. Once downloaded, sort out anything really good and retain as a large file, then resize/compress the rest. That way you keep your options open and get the best of both worlds. Or you could simultaneously shoot raw plus low quality JPEG. That way you've got a high quality image if you shoot something special, otherwise just delete all the raw files from your computer and retain the JPEGs.

It seems a shame to pay a lot of money for a camera capable of high IQ then deliberately cripple it by taking low resolution shots. You can do that on a smaller, lighter and cheaper P&S! Just my opinion.....:smile:

 

[Gusnyc]

Thank you very much for the answers! Very illustrative!

As a graphic designer, every time I received a JPG for printing (not the ideal case) I really preferred higher pixel count, but I am talking about images that were going to be sent to the press.

For me now, photography is about enjoyment. Again, I am not planning about printing sending my pictures to a contest or making money from them. I understand the benefits of RAW images, but at this moment, the cons of that format are bigger than the benefits. I like to have all of my images in my laptop because I like to browse and edit some of them every time I have time to spare. That could happen at night or on a plane or in a long commute. Working on-the-go is fun for me. The same when I connect the laptop to the cinema display.

I think JPG is adapts to my actual need better than RAW at this moment. I don't want to take low-low resolution pictures, but I think having a library in RAW (again, at this time) would be a waste of space in my hard drive and time (processing the images).

I really appreciate the time you guys took to answer. This information is very useful for me, even if I don't immediately start using RAW, it help me to understand the format and its workflow much better.

What a great group of people you are!. Seriously.

Gus

 

[squeegee]

It might actually be a combination of both. The reason is compression quality is not linear - as in the last 10% (90-100) is not as noticeable as say 10% at 40-50, but the file size difference at the last 10% is huge where it's negligible around the middle.

Here's an actual photo example to think about (using an e-p1)

large super fine image is at 99% jpeg quality : 6,592 kb
if I change the compression after to say 92% : 1,777 kb
at 86% : 1,208 kb

The reason I picked 92% is because I find that's my favourite compression level, it's where the image size ceases to drop drastically but the quality (for me) is un-noticeably worst. There's people who say 86% is not-noticeable but I can almost always see it's worst at that level, and if you notice the file size difference... it's not much, so I stay with 92%.

Here's pixel size examples :

large super fine 99% : 6,592 kb
2560x1920 99% : 2,354 kb
1600x1200 99% : 897kb

large 92% : 1,777 kb
2560x1920 92% : 748 kb
1600x1200 92% : 283 kb

So as you can see, changing the compression just to the 92% point makes a drastic difference in the file size, much more than scaling it down 1 ratio. I would personally take a 92% 2560x1920 image over a 1600x1200 99% image any day. I doubt many people would notice the quality difference between 99% and 92%.

Notice how much smaller the 1600x1200 at 92% is compared to everything else. I can't imagine you'd be looking for anything smaller than that.

Don't take my word for it though, test it out yourself. Your camera etc may have different sizes / compressions as mine. Take a picture, play with saving it as different compressions, and different sizes. I'd always advise on photo-ing it at full size and quality though - but that's just me.

P.S. my e-p1 usually uses 92% for "normal" mode, although I think I've seen it go lower on rare occasion.

 

[Gusnyc]

Thanks Squeegee, that is exactly the kind of information I was looking for!