file compression without affecting IQ?

Pentaxor · 07-29-2009, 12:55 AM

hi guys.

I just want to ask what kind of software that you use to compress your jpeg picture files without affecting the image quality? or probably a site where you could upload the original file as huge as 9mb?

problem is I got 9 mb photos that I want to compress inorder to upload but whenever I compress them, they lose a huge amount of detail. and the images began to show huge amount of discoloration and smudging (especially when cropped 100%) which were absent or non-existent in the original jpegs. though the compressed images may appear fine or really good in small standard prints, but it doesn't really give justice to the original image. I ask if any of you know or have anything that could solve this. mind you that this is jpeg to jpeg, not raw.

here is a sample of a compressed image. original is too big to be uploaded. I would be happy to upload it as well if you could direct me to a site which doesn't have a file size quota. thanks

procyon · 07-29-2009, 01:35 AM

What software did you use to generate these 9MB jpeg files ?
Does it have an option to change the amount of compression applied to files when saving ?
You just have to find the setting that compresses enough and does not sacrifice quality too much (for your uses). There is no way to compress more without losing quality more.

Pentaxor · 07-29-2009, 01:52 AM

sorry for the blunder, I meant 3.5 MB and not 9 mb. guess I'm not thinking clearly anymore for lack of sleep. but anyways, I'm using ACDSEE as of the moment. and yes, there is an adjustment as to how much you want to compress. if that was the case, well, what a bummer that would be.

*Ash* · 07-29-2009, 04:22 AM

Most JPEG converters and image editors have JPEG saving option prompts when you come to save the images. Resizing shouldn't degrade IQ significantly (unless the dpi is <70 or so), but JPEG compression does. So choose high quality at this prompt...

**Marc Sabatella** · 07-29-2009, 09:31 AM

There are two things you can do to reduce the size of an image file - either reduce the number of pixels (resolution) or increase the amount of compression. While both can be apporpriate, for web use, you should be concentrating more on the former than the latter. That is, if you reduce the number of pixels to a level appropriate for web use, chance are, you won;t need to apply much compression.

I'm guessing you are leaving your files full resolution but compressiong the heck out of them to make the file size smaller. When you upload the image, the site you are uploading to is probably looking at the resolution and saying "that's still way too many pixels" and then reducing the resolution too. So you're getting the worst possible results. Had you reduced the resolution whatever level the site supports (many sites have a maximum of 1024 pixels on the longest side, for example), you probably wouldn't have needed much compression at all, and the site upload software wouldn't have had to then reduce your images further. JPEG always applies *some* compression, but if you resized your images appropriately to begin with, you could use 90 in your JPEG quality setting in ACDSee, for example.

If you're concerned with reducing the number of pixels, remember - the site upload software is doing that for you anyhow, because no one has a screen nearly big enough to display a full resolution file from a 14MP camera.

Pentaxor · 07-29-2009, 10:37 AM

thank you all for your replies. I adjusted the compression just a lil bit (enough to fit in the 1mb capacity limit) and retained as much as 85% of the original IQ of the photo.

here is the sample of the better version. as you can see, there is not much obvious color and detail smearing as opposed to the first photo. (take notice of the shadow parts in the upper left side and upper right side), thus showing a photo of much finer detail. in the first photo, there is a moderate yellow tinting on the left side and purplish discoloration of the shadow on the right side. now this noticeable smudges are gone in the new compressed photo. for reference, I think the EXIF data is available.

**Marc Sabatella** · 07-29-2009, 11:42 AM

That's still *way* more JPEG compression than you needed to get the picture under 1MB, given that the image is being displayed at only 640 pixels. Had you resized to 640 pixels in ACDSee first, you could probably have set compression to the minimum (quailty = 100) and still been way under 1 MB.

Pentaxor · 07-29-2009, 03:23 PM

Originally Posted by Marc Sabatella

That's still *way* more JPEG compression than you needed to get the picture under 1MB, given that the image is being displayed at only 640 pixels. Had you resized to 640 pixels in ACDSee first, you could probably have set compression to the minimum (quailty = 100) and still been way under 1 MB.

no Mark. the website did the resizing for me. but anyways, regardless if I resized it with ACDSEE or in the photo sharing website, the results are the same. the IQ is diminished at a certain extent and the only way to avoid or retain the same IQ value is to compress the file under 1 MB and upload it with the same original pixel resolution size. otherwise, shoot a picture under 2MP resolution with a much smaller file size. but of course, the picture wouldn't look nice when cropped.

at 640 to 1280 mpixel viewing, I think the photos would appear fine. unless it is used for large prints or cropping images. thanks again.

p.s. , your suggestion about acdsee resolution resize + 100% quality conversion and compresion worked. the file size was much smaller, about a quarter of an mb and the IQ was exactly almost the same as that of the 2nd photo with about a 1mb file size.

the first photo however, is just a mess.

**Marc Sabatella** · 07-29-2009, 11:06 PM

Originally Posted by Pentaxor

no Mark. the website did the resizing for me.

I know. That's my point. If you had done it yourself, you wouldn't have needed any but the absolute bare minimum amount of compression. As it is, you applied compression unnecessarily.

but anyways, regardless if I resized it with ACDSEE or in the photo sharing website, the results are the same. the IQ is diminished at a certain extent and the only way to avoid or retain the same IQ value is to compress the file under 1 MB and upload it with the same original pixel resolution size.

This is precisely backwards. The way to get maximum quality on a web upload is to reduce it in resolution to the level required yourself. This will allow you to get the file size under the threshold with virtually no compression required. Compressing it first then letting the photo site reduce the resolution is just applying compression unnecessarily. Although at only 640 pixels, you're not likely to notice the difference, which might be why the results *seemed* the same either way.

Pentaxor · 07-29-2009, 11:56 PM

maybe there is a minimal difference. but both did show some stretching along the corners of the lens barrel as you cropped both images. that is understandable since both photos were already set at 640.

thanks for the tip. I'll consider reducing the resolution when I'm compressing some photos before uploading them as is.

dylansalt · 08-01-2009, 03:56 AM

Have tried many programs but imho opinion the easiest to use with phenom results is Fastone Image Resizer (Free) - when resizing I normally add a sharpening factor of +2.

Before I upload to my Flickr site and then down to this forum gallery I always use Fastone.

Am always amazed how small it (kb) can make a tiff/bmp file with zero loss in image detail.

Dylan