jpg to tiff

[act]

Does anyone see any advantage to shooting in jpg and then converting to tiff

other then being able to save space on your camera's memory card and then

storing the image in a lossless format on your computer?

 

A second question I have is how many times can you copy and save a jpg before

you start to see a loss in image quality?

 

Thanks

[ericf1]

The problem is by only recording in jpg you've already lost data versus shooting in RAW.

 

As far as copying a jpg file, the mere act of copying the file does not affect the image quality.

 

Good luck.

[rconey]

I had a jpg picture of one of my kids that got saved a few times and started to look really funky/pixillated. I haven't done the experiment to see what is required to make this happen. I do now at times shoot jpg and then save tif or photoshop format for lossless storage.

If I want all the data, i shoot raw to begin with.

[steve_dunn2]

<cite>Does anyone see any advantage to shooting in jpg and then converting to tiff other then being able to save space on your camera's memory card and then storing the image in a lossless format on your computer?</cite>

 

<p>As someone else pointed out, the act of saving the file as a JPEG in the camera loses information. Converting to a TIFF afterwards will prevent any further loss, but it can't reverse the loss that took place in the camera. If you use the camera's highest quality setting, the loss may not be visible; you'll have to make the call as to whether that's an acceptable trade-off to save space on the memory card. To me, memory cards aren't expensive, and I'd rather have more memory cards and higher image quality than fewer memory cards and lower image quality.</p>

 

<cite>A second question I have is how many times can you copy and save a jpg before you start to see a loss in image quality?</cite>

 

<p>Copying? No loss. Saving? Loss, though how much of a loss depends on the options you choose for saving. If you repeatedly open and re-save a file using the highest quality setting your image editor supports, you'll probably not see the degradation for a few open/save cycles. Doing it even once at a medium quality setting will result in visible degradation.</p>

 

<p>The bottom line is that any lossy compression scheme is unsuitable for use as an intermediate format, because once you've thrown away that information, you will <em>never</em> get it back.</p>

 

<p>One other thing to point out is that if you're comparing JPEG to RAW, you're not just comparing lossy compression to lossless (or no) compression*; you're also typically comparing an 8-bit image that's had a bunch of processing done to it with a deeper (typically 12-bit) image that hasn't had a bunch of processing done to it. Even if JPEG compression were lossless, the RAW file would still be a better starting point for high-quality images, due to the greater depth and the fact that it hasn't had any irreversible processing done to it.</p>

 

<p>*: for all I know, there may be cameras out there that use lossy compression for RAW files. I'm from the Canon DSLR world, in which RAW files are compressed losslessly.</p>

[eugene_scherba]

<p><i>Does anyone see any advantage to shooting in jpg and then

converting to tiff other then being able to save space on your

camera's memory card and then storing the image in a lossless format

on your computer?</i></p>

 

<p>Does anyone see any advantage to chomping up your kid into little

slices in order to fit it into carry-on luggage and then stitching

it up together after the flight?</p>

[evan_goulet]

Just as an aside that is somewhat relevant to your second question, I was bored at work while waiting for the spectrometer in our lab to cycle through, so I went ahead and did a little test. The only image I had on my computer was a scan from a slide at 4800 dpi. It was soft to begin with as the shot is a reflection in a really grimy mirror mosaic, but I digress. The comparisons are of the base image (100% crop) saved once at JPEG compression level 7 in Photoshop against an image that was saved 50 times at JPEG compression level 7. You can see a muddying of the tones in the image, particularly around the eyeline. <P><img src="http://i9.photobucket.com/albums/a85/ofofhy/Imagecomparison.jpg"><P>I included the histograms for each of the crops (minus the text of course), and you see peak sharpening in the 50x version that indicates the tones are getting compressed into bands. <P><img src="http://i9.photobucket.com/albums/a85/ofofhy/Histogramcomparison.jpg"><P>If you look at the images at 200x, you can see some exaggerated pixelation starting occur. If I find a bit more time (and with the spectrometer constantly running I have plenty of it) I may try other compression levels.

[evan_goulet]

Should have pointed out that the base histogram is on top, and the 50 x histogram is on the bottom there.

[barry_sanford]

I have never found an advantage to shooting in jpeg then saving in tiff. The only time I have

ever converted to tiff from jpeg is when the jpeg was all I had to begin with (not by my own

choice). By saving in tiff, I could be assured that the tiff held the expanded jpeg at its best

before continued save operations made it worthless.

[patrick_viebey___orlando__]

The only time I would 'transfer' to TIF is if I felt I wanted to save an original in an editable mode, or if I was gonna edit it, and then give it to someone else (who might wanna edit it).

 

You will lose image quality every single time you save - JPEG compression is *by definition* lossy, which means data is lost. The amount depends a lot on the quality of the image to start with, what JPEG settings you use, and ummm, how good your eyes are (and what you're going to do with it).

 

Hope this helps.

[rconey]

Let me correct myself. I went back to the same picture I used in a yearbook page and went through 6 save-close-open-resave cycles at 12 then level 7 quality save in photoshop. I can't see any difference in the two images, so the time before I must have done something else to goof the picture. I am surprised how similar the two pics above are after 50 save cycles (thanks for the data). It seems that .jpg saves once done are pretty consistent in the data they keep.

The lesson is still to shoot raw for important images, jpg for less important ones.