14MB to 8MB by rotating tiff = quality loss?

[stefG5]

i just batched all my jpg's to tiff24 format so i dont loose quality by working with them. i then ran a few through a PS script to rotate and then save them

this reduces the filesize by as much as 50%! should i assume this will be reflected in the image quality? but thats the whole reason why i put them to tiffs in the first place.

thanks for any advise on this

stefan

[Scottes]

Did you have LZW Compression enabled for the save? Did the action convert to 8-bit?

Other than those 2 things there's no reason why rotating a TIFF would reduce file size.

[stefG5]

yep its the LZW compression. for reference, you need to do "save as" after which the window appears where you configure this. i need to adjust my script. thanks very much.

is this really lossless? i mean REALLY lossless

[Hellashot]

To begin with you're already behind the 8 ball by starting from JPGs. You need to shoot in RAW if you can. I rarely save anything besides the RAW. 16bit TIFFs take up too damn much space, and mine are only 6MP images.

[Steven M. Anthony]

To begin with you're already behind the 8 ball by starting from JPGs. You need to shoot in RAW if you can. I rarely save anything besides the RAW. 16bit TIFFs take up too damn much space, and mine are only 6MP images.

Yeah--converting to tiff after shooting jpeg is like closing the barn door after the horse gets out.

[Scottes]

LZW is absolutely lossless. No doubt about it. It simply records the number of pixels (or patterns of pixels) in a row that are the same exact values. It does not try to average the pixels like JPG does.

You have to watch LZW because of this. In some images - particularly high ISO ones - the image may not have many repetitive patterns with identical values, or the patterns may be very short like 3 or 4 pixels. In cases like this LZW will take a long time trying to find patterns and can end up increasing the size of the file. This is because each pattern adds an entry into LZW's table, and with many short patterns the table ends up being quite large which increases the image size.

Because of this I rarely use LZW since - in my images - the average space saved is not worth the time to wait for LZW to compress and decompress. Your mileage may vary.

[robertwgross]

A long time ago, back when GIF was king, and when GIF files were beginning to get large, the 24-bit TIF format was OK, but TIF-LZW was very useful. In some cases, it would "pack" an image file to a reasonable fraction of the original file size. After a while, I noticed that some of the TIF-LZW files were almost as large as the original. In a few cases, the TIF-LZW was actually larger than the original, despite all the "packing time" used. It is then that I realized that high resolution files with lots of detail do not pack very well in TIF-LZW.

So, you can rotate from TIF to TIF, or from TIF-LZW to TIF-LZW, and there will be no further loss. Going from TIF to TIF-LZW may get mixed results. However, starting off from JPEG was the original step in the wrong direction.

You are shooting RAW, aren't you?

---Bob Gross---

[soko]

There is an underlying theme in the knowledgeable posts above about shooting raw but not everyone does. I shoot raw but people have reasons not to, like their cameras don't have the facility, not so convenient with lower end models ("Post Processing...." is not exclusively a DSLR forum) or some other reason (maybe good, maybe not so good). Then shooting JPEG and converting to TIFF for any post-processing involving resaving is absolutely best practice.

[Scottes]

Then shooting JPEG and converting to TIFF for any post-processing involving resaving is absolutely best practice.
In this context, I agree wholeheartedly. Beyond a shadow of a doubt.