Questions tagged [image-compression]

Image compression comprise methods with the goal to reduce the size of an image by either removing redundant or less important information (or a combination of the two).

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58
votes
1answer
17k views

Are “Windows Photo Viewer” rotations lossless?

Can I rotate lossily compressed photos that I view in Windows Photo Viewer without worrying about losing even more information to compression?
57
votes
7answers
20k views

Why don't most cameras support PNG format?

I prefer PNG format to JPG, because JPG uses lossy compression. When I capture a screen in my PC or scan a picture or document in my scanner, I always save them as PNG format. If a camera could ...
41
votes
6answers
160k views

What quality to choose when converting to JPG?

When you export a picture to JPG you can normally choose its quality in a 1-100 scale. I like to keep a good quality but it wouldn't make sense to keep a JPG that will be almost as big as the original ...
30
votes
4answers
6k views

What factors cause or prevent “generational loss” when JPEGs are recompressed multiple times?

For years, I've believed that recompressing JPEG files multiple times would gradually degrade its quality until they are an unrecognizable mess, the way making photocopies of photocopies does. This ...
30
votes
5answers
4k views

Why don't cameras support JPEG 2000 format?

The original JPEG format was updated in 2000 to provide a variety of features including less artifacts, better compression and lossless compression. Why haven't cameras updated to use this new format?...
29
votes
6answers
35k views

How can I tell exactly what changed between two images?

For example, for a recent conversation about JPEG compression I wanted to compare pixel for pixel what changed between two JPEGs (one with compression level 100, and one with compression level 95). ...
25
votes
12answers
38k views

Does simply opening and closing a JPEG file decrease image quality?

I've had quite a few photography classes, read many photography books, and screened many forums. And I can't find a consistent answer to this question. One "camp" says there is a loss of image quality ...
24
votes
6answers
37k views

What are jpeg artifacts and what can be done about them?

I know JPEG is a "lossy" compression algorithm that discards information in order to save space. What is the visual impact of this? I've heard of "JPEG artifacts". What do these look like? Are there ...
21
votes
3answers
27k views

Which TIFF image compression is better, LZW or ZIP?

Which image compression is better, LZW or ZIP? I am using Lightroom to export images.
21
votes
2answers
6k views

Google Photos high quality backup — how does Google achieve great compression and am I losing some data?

I'm sure that many of us have used Google photos high quality backup which allows us to store photos online without fees. Recently, I thought of testing just how high quality the uploads really were ...
19
votes
3answers
9k views

Why does JPEG quality go up to twelve?

Wwhy does the JPEG quality option in Adobe products go up to twelve? Here's the option in the Save dialog of PS: Thats a whole new definition of it goes up to eleven.
17
votes
3answers
10k views

Does Flickr recompress JPEGs after upload?

Does Flickr recompress JPEGs after upload? I know that if you upload a TIFF, for example, Flickr converts it to JPEG. But do they also compress incoming JPEGs? I've read some complaints about the ...
14
votes
3answers
5k views

Is there a lossy compressed file format for 16-bit dynamic range images?

I'd like to aggressively compress some scientific 16-bit grayscale image files, but without reducing the dynamic range. Is such a thing possible? I understand that JPEG format uses lossy, and ...
13
votes
4answers
18k views

How to avoid jpeg compression artefacts when saving photos in web resolution?

When I save a web-resolution image (for example, 1920×1024px), flat areas tints often have damaged shades of color. I'm saving in Photoshop CS4 with quality 2 in standard mode, because I need the ...
10
votes
4answers
30k views

Why are two pictures that are the same dimensions/dpi such different file sizes?

I am working on a project where two my images must be AS SMALL AS POSSIBLE. I have scaled two images to the same dimensions/dpi and I've checked the color profile in Photoshop CS6 and they both look ...
9
votes
2answers
518 views

Is there a middle ground format between RAW and JPG?

JPG files use 8 bits per color per pixel (I've never heard of any camera that uses the alleged 12-bit-per-color-per-pixel extension) and is a compact way of storing images. RAW files are huge but ...
8
votes
3answers
4k views

Does JPEG-to-JPEG export Lightroom reapply compression?

I want to crop a JPEG file in Lightroom and export that cropped file to another JPEG so that I can e-mail it. The exported JPEG should have the same quality as the original. I don't have the RAW file ...
7
votes
10answers
159k views

How to reduce the file size of my photos (to under 15 MB)?

I don't have a "Pro" account on Flickr, just the free one, so my photo uploads are capped to 15 megabytes/file. After post-processing, my photos end up being too large to be uploaded to Flickr. I do ...
7
votes
3answers
3k views

Make photos on Facebook nicer?

I upload photos to my Facebook page using the latest Lightroom. I'm wondering if there are some tips or tricks, or maybe hidden options on Facebook that makes the images served to the viewers higher ...
7
votes
4answers
13k views

Is it not ideal to save image as PNG for printing?

So the scenario: I want to order a print of one of my images. It is a special image and will be relatively large (a couple of metres) so I want it to be perfect as possible. I have the RAW file, ...
6
votes
4answers
5k views

Why does Darktable export enormous JPEGs?

I have a Nikon D3200 and just started shooting in Raw. Raw files are 18-24mb, and if I convert them to JPEG using Nikon's ViewNX 2, I get 8-12mb files at the top quality and resolution using sRGB; ...
6
votes
2answers
2k views

How does the usual jpeg 0-100 quality settings translate into Photoshop's 0-12 quality setting?

JPEG encoders usually use a quality setting of 0-100, whereas Adobe photo software uses a 0-12 setting. Does anyone know how to convert between these? (I am actually not clear on whether the 0-100 ...
6
votes
2answers
1k views

What kind of artifacts will Nikon's lossy NEF compression algorithm cause?

The D7000 has two options for NEF compression: "Compressed" and "Lossless compressed" -- the manual says NEF images are compressed using a non-reversible algorithm, reducing file size by about 40-...
5
votes
2answers
4k views

Is it possible to find out what compression ratio was used for a particular JPEG?

I have a couple of JPEGs. Is there a way to find out which compression level was used when encoding them? That is, were they encoded at level 60 or 90? The reason I'm asking is because I have a site ...
5
votes
1answer
1k views

Does writing EXIF tags influence jpeg quality?

If I understand well then the EXIF data is written in an extra space of the JPEG file. When I add or modify an EXIF tag does this leave the picture untouched? I searched for this and I was not able to ...
5
votes
1answer
493 views

Understanding Hue, and is there something else I should be using?

I am trying to isolate objects of a certain color in an image. Looking at this image, you can see that I have extracted the hue channel, and have filtered these values so that the closer a pixel's hue ...
4
votes
5answers
2k views

How can I resize more than 2GB of travel photography with no quality compromise?

I have more then two gigabytes of travel photography. Each image takes up than 4 to 5 megabytes. I have to send them to some one. How can I resize all images while retaining high image quality?
4
votes
2answers
2k views

Why are JPEG images from camera huge and the same images exported from Vistaprint software 10 times smaller?

JPEG images from my Nikon D3300 are roughly 12-15MB big at 6000 x 4000resolution. RAW images converted to JPEG through LightRoom are also 12-16 MB. I recently created an album through VistaPrint ...
4
votes
3answers
1k views

Quality of JPEG directly from RAW+JPEG versus JPEG embedded in RAW of RAW+JPEG?

When I use ImageMagick's identify command to look at the quality of the JPEG from my camera's RAW+JPEG mode, I see 95. When I use the same to look at the JPEG preview that has been directly extracted ...
4
votes
5answers
4k views

What is difference between 8bit RGB and 16bit RGB?

Most of time when I open any images to Photoshop, it shows 8bit RGB format, but I have also seen 16bit RGB. As a trial, I copied one image and pasted it into a 16bit RGB blank image, but I didn't get ...
4
votes
3answers
5k views

Best program to batch compress JPGs with minimal loss?

My photo catalog is getting bigger and bigger. It's mainly my fault because in my noob years I used to export all JPGs with a 100% quality, point at which files can reach the 10mb mark or even more. I ...
3
votes
4answers
638 views

Why do modern DSLRs support JPEG but not lossless formats other than RAW?

I'm from a programming background and very new to photography. While working with the SDK for the Canon Rebel T3i, I realized that the only image formats natively supported by the camera are RAW (CR2) ...
3
votes
4answers
24k views

What image quality is lost when re-saving a JPEG image in MS Paint?

Has anyone ever noticed that if you open a image in mspaint (.jpg, .jpeg) and then just save it, the image size is reduced by many folds. I use this method to reduce the file size. However, I am not ...
3
votes
3answers
7k views

Why does simply saving a JPEG at 100% quality in Photoshop increase filesize?

If I take a picture taken with my EOS 60D, put it into Photoshop, edit it as I wish and save it as JPEG with maximum quality, the file goes from 5 to 12 mb in size. Obviously if I didn't increase the ...
3
votes
4answers
17k views

Does converting RAW files to TIFF lose image quality?

Before I found out about Camera Raw, I used to convert my photos from RAW to TIFF, using the XNVIEW convertor, downloaded from the Internet. My question is whether I lost image quality or anything ...
3
votes
1answer
296 views

Should I resize photos before or after image optimization?

I am a software dev who appreciates stunning imagry in sites I build, but am also very conscious of page size. My workflow has me adjusting image sizes to the maximum resolution they will be displayed ...
3
votes
1answer
517 views

What are the anomalies in this picture of earth?

I was playing around with the New NASA pic of earth (posted July 20th 2015 on Nasa Goddard space flight center on Flickr). I've found this very odd structure on the bottom right corner that is pretty ...
3
votes
3answers
3k views

Does reducing Lightroom export file size reduce image quality?

Sometimes I reduced the file sizes of my jpeg images for faster uploading to the web. Does this reduce the image quality?
3
votes
1answer
537 views

What is the relationship between ARW delta compression and dynamic range?

I read this article about the fact that Sony AWR is not a lossless RAW format, but, rather, an 11-bit + 7 delta compression. According to DXOmark, the dynamic range of A7r is 14.1, as opposed to 14....
3
votes
4answers
589 views

What is the best practice for batch compressing jpeg files?

This is fairly theoretical, as it is definitely in the realm of "pixel peeping" and is more or less irrelevant for practical use, but with the increasing popularity of full-width images on websites, I'...
3
votes
2answers
465 views

How can I simulate JPEG quality degradation? [duplicate]

I am writing a report about file formats in images & their properties. In the report I want to talk about how file formats have lossy compression rather than lossless compression & I wanted to ...
3
votes
2answers
12k views

Reasonable file size for printing high quality photography as A3 posters?

I bought some photos and need to send them off for printing. The printing company asked for the final files to be in PDF format, so I've converted them using Illustrator and Photoshop. I also added a ...
2
votes
2answers
736 views

Does a JPEG image uncompressed to bitmap prior to displaying it on the screen [closed]

Does a JPEG image converted back to bitmap image when displayed on the screen? Does it occupy more memory than the actual file-size when it is being displayed? Does JPEG images, if added to the web-...
2
votes
2answers
552 views

Good compromise on quality/compression for hi-rez photographs?

My Nikon D90 dumps out photographs that are 4288 x 2848 @ 300 DPI. They're about ~3 MB in size. I'm an amateur in every sense of the word. I don't know what 75% of the camera settings do. I'm ...
2
votes
3answers
341 views

why won't my photos compress past a certain size?

I'm having issues compressing my film scans to a suitable size for use on my website. for example, I have a .jpg file with a size of 17.4 MB. I opened the photo in Photoshop and tried two methods: ...
2
votes
7answers
1k views

Compress a few small areas of an image in higher quality

I would like to prepare a photo to display it on a webpage. I would like to compress this image such that most of the image is compressed to lower quality, to reduce download size, but a few small ...
2
votes
3answers
354 views

Lossy but essential: is there a modern file format useful for modern camera files?

I remember the early digital cameras that had anything resembling useful quality (megapixel) stored JPEG files that were noticeably lossy. As memory cards became more capable, this was addressed and ...
2
votes
1answer
171 views

Watermarking processing proof

There are watermarking technologies in videos that are resistant to transcoding and image resizing. There are no visible artefact, it's rather for content protection and tracing. Is there anything ...
2
votes
5answers
3k views

What is the real world impact of the lossy compression used for NEF RAW files in some Nikon cameras?

I intend on buying a DSLR in the near future and my eye has been stuck on the Nikon D5300. One of the things in photography that I feel uncomfortable with is compression, therefore I obviously care ...
2
votes
1answer
174 views

What are the benefits of LZW compression for TIFFs?

I have few photos - JPEGs from smartphone, RGB, 8 bit per channel. Nature, landscapes. I want to edit them. Before editing I will convert JPEGs to TIFFs. I will use TIFF, RGB, 8 bit per channel. ...