Photoshop LZW colors and sharpness

[Fetih]

Hello, I do digital printing on textiles. It is important for us that the colors we work with are clear and that the colors remain the same after printing. If we save the files with LZW, will we have color and clarity problems in printing?
Changing even a single tone will cause the color to appear different.

[Stephen Marsh]

LZW is lossless, so if you are currently successfully saving uncompressed TIFF files, then LZW shouldn't change that.

[Fetih]

Why doesn't compression without distorting any pixels and tones feel right to me?

What does it reduce without reducing the size of the image and colors?

[Stephen Marsh]

Why doesn't compression without distorting any pixels and tones feel right to me?

What does it reduce without reducing the size of the image and colors?

By @Fetih

Perhaps it doesn't feel right to you because you don't understand lossless compression and perhaps only know of lossy compression such as JPEG.

There are different ways of encoding data, which may (or may not) make a file smaller in file size. Generally, the trade-off is in slower saving times than with uncompressed data.

Imagine the following fictitious example:

1, 2, 3, 4, 5, 6, 7, 8, 10, 15

vs

1-8, 10, 15

Nothing has been lost, both methods express the concept of the numbers 1 through to 8, however, the second is "more efficient" as it takes up less "space" than the other (but needs encoding and decoding to restore the missing range of digits from 2 to 7).

The easiest one to learn about is RLE:

https://en.wikipedia.org/wiki/Run-length_encoding

I'm not going to even try to explain lossless LZW or ZIP compression, you can read up on that yourself:

https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch

https://www.techtarget.com/whatis/definition/LZW-compression

[Fetih]

Your answer may be correct, but I'm still not convinced 🙂

If LZW is a lossless option, why did Adobe offer it as a separate option?

1-) Recording, save in large size and lossless.

2-) Save, save in small size and lossless. ( LZW )

3-) Save, save in small size and lossy. ( zip and jpeg )

If the 1st and 2nd options are the same, why were they presented to us due to the size difference? Wouldn't it be more appropriate to just make LZW recording standard?

[Stephen Marsh]

Your answer may be correct, but I'm still not convinced 🙂

By @Fetih

To quote the classics:

I find your lack of faith disturbing

[Fetih]

It is not normal for you to be disturbed by my belief. I asked why Adobe offered us these 2 lossless options. If LZW is lossless, why doesn't it replace standard recording?

[Derek Cross]

Fetih – you seem obsessed with formats – choose PSD, TIFF, (uncompressed) JPG or PDF and get on with the real issue of colour fidelity in CMYK (or CMYK+) printing, which is having an understanding of the different gamuts of RGB and CMKK modes and, as mentioned,  implementing colour management for your workflow.

[josantgomez]

Estaba leyendo esta muy interesante "tertulia" y ahora encuentro, leyéndote, que hay la posibilidad de JPG sin comprimir.

No recuerdo haber visto esta posibilidad al guardar un archivo. En Photoshop, por ejemplo, ¿dónde se eligiría?

[Stephen Marsh]

@josantgomez – no, I believe that was a typo!

I believe that when @Derek Cross wrote:

choose PSD, TIFF, (uncompressed) JPG

It should have read as:

choose PSD, TIFF (uncompressed), JPG

Again, there is no data loss when using LZW or ZIP compressed TIFF.

[Per Berntsen]

When saving an 8-bit tiff, there are four options for compression.

None uses no compression, and produces a standard Tiff file. It is neither lossless nor lossy – no compression at all.

LZW uses lossless compression.

ZIP uses lossless compression.

JPG uses lossy compression.

LZW is very effective with 8-bit files, but can increase the size of a 16-bit file.

ZIP is the most effective option for 16-bit files.

[D Fosse]

@Fetih 

This is very simple: Compression takes time. There's a lot of math. Saving uncompressed is much faster.

If you work with really big files, it can be 15 seconds vs. 2.5 minutes. Which one do you prefer?

Besides, as Per points out, LZW doesn't really work for 16 bit data. It was written for 8 bit data, which was the norm back then.

[D Fosse]

Stephen explained it very well.

Lossless compression will not change color numbers. That's why we call it lossless.

Lossy and destructive compression like jpeg may, so don't use that. The jpeg algorithm compresses the color component more aggressively than the luminance component.

However, Derek has a good point. It is crucial that you follow good color management procedure here. You need to have icc profiles for your printing process, and you need to always work with material that is defined by an embedded icc color profile in the document. You also need to work with calibrated and profiled displays so that the correct color will actually display on screen.

This is all standard procedure and not complicated, it just needs to be implemented.

[Conrad_C]

Just as supporting information, be aware that LZW is the most trusted of compression methods for TIFF files, historically speaking. Since the 1980s, prepress companies have advised clients to save TIFF files as either uncompressed or with lossless LZW compression. Photoshop offers several other compression methods for TIFF, but they are not nearly as widely used for various reasons.

So there’s an established industrial history, spanning about a third of a century, of people using TIFF with LZW compression for all kinds of professional jobs on press.

If a compression method is lossless, it’s a little like a folding chair: It really can take up less space without losing any of its functional qualities. Not losing quality does limit how small you can make a file using lossless compression. Because you can make an image into a much smaller file using lossy JPEG compression, but because that’s lossy, it will cost you some quality.

[Fetih]

I would like to thank each of you individually. This information has cleared up enough question marks.

[Derek Cross]

Are you using Screen printing and, if so, are they spot colours or CMYK?

[Fetih]

Digital printing, paper to fabric printing. RGB profile

[Derek Cross]

Sounds like you should be employing normal colour management workflows including calibrating your monitor, using appropriate profiles for your printer and so on.