Any benefit to converting jpeg to tif for manipulation?

[bill a.]

I liked my F10 and now the F30, but there is one drawback: jpeg only -- no

lossless formats (TIF or RAW).

 

This may be a stupid question, but knowing that jpeg is a "lossy" format (I

understand you lose information simply rotating the image), is there any

benefit to taking the raw jpeg, and converting it to tif, and doing any

manipulation from there (in the case where you know you will be manipulating

the image)?

[alyson]

yes, definitely convert to tiff or psd for processing and then you can save out your final as a

copy in jpg format if you like.

each time you save while working on the file, you'll be re-jpegging, ie, re-compressing and

thus degrading the image, and you save frequently while working of course.

[inspiration point studio]

You don't lose image quality by manipulating a jpeg file. You only lose quality when you save

a file in jpeg format. When you start with a jpeg file, save it right away using a non-lossy

format (e.g.

tiff, psd) and make that your master copy. You can edit the file subsequently and save it

numerous

times without losing any quality. If you need a jpeg file for the web, use the SAVE AS

command to save a separate jpeg copy.

[peter_white2]

Michael is correct. And, if your camera has any options for jpeg size or compression or quality when shooting, always use the largest possible file size, lowest compression, highest quality, lowest number of images, etc. Get the most data you can start with. Then, when you download the images, save them as tiff or psd, and go to town.

[v.anisimov]

Agree with Michael. You only lose quality when you re-save JPGs.

 

On a side note, I used the F10 for some time and it was great. However, I wouldn't be so concerned about the presumed JPG losses with such camera. The F10/F30 are designed for low light, candid photography. One doesn't expect to use it for a 20x30" landscape poster where every bit of quality matters. I felt comfortable editing and re-saving once as JPGs at the lowest compression setting. With an iso 1600 image from an F10, JPG losses are the least of your concerns.

[dave_powell1]

Ditto on all the above reponses. Michael's statement about JPEG's losing slight quality when saved is true...in fact, you lose a little quality (through additional compression artifacts) if you open and close a JPEG file without even manipulating it.

 

Before you save your TIFF "working" file, you may also want to convert it to 16-bit mode (or even 32-bit mode in Photoshop CS). This is especially valuable for upsampling images, because it gives Photoshop MANY more tones to apply to the pixels it adds. This produces smoother tonal gradations, and less "banding" in digital enlargements.

 

(Of course, you'll need to convert the file back to 8-bit mode to save it as a JPEG for printing.)

 

NOTE: 16- and 32-bit files do take up more storage space than 8-bit files!

[ilkka]

If you open a jpeg file and close it without saving it, there is no way you can lose quality. You have not altered the original file in any way. But some programs do save the file again after opening it, without even telling about it.

 

Instead of converting all jpegs into Tiffs for further processing, I would suggest keeping all the originals as jpegs and only saving a new master copy as tiff once you start doing any adjustments to the file. This saves a lot of space. The quality of the original jpeg does not change if you keep it for a year instead of for a day. The important thing is not to save a work copy as jpeg, but always as tiff or psd. Once all is done, depending on use, you can save a second copy as jpeg since it takes less space. But it is good to keep the worked original as tiff.

[dave_powell1]

You're right, Ilkka... you can't lose JPEG image quality if you only open and CLOSE the file. But, I was pointing out to Bill that you CAN lose JPEG image quality if you repeatedly open and SAVE the file, even if you do nothing to it. This might seem like a silly thing to point out, but read on!

 

When an image is first JPEG'd, a few small compression artifacts creep in...which obliterate a tiny, tiny bit of image data. (Magnified, these artifacts look like short straight lines in the image or...in extreme cases...little "checkerboarded" areas of tone.) The JPEG'd image now includes artifact pixels that weren't in the original image captured by the camera's sensor sites. (For this reason, try comparing high magnifications of both RAW and JPEG files of the same image...which some cameras now provide.)

 

Now, open the JPEG again and immediately save it without doing anything to it. The JPEG algorithms are now re-compressing a slightly different image...differing specifically in the compression artifacts added earlier. If you keep opening and closing/saving the file without doing anything else to it, more and more compression artifacts are added and re-compressed at each stage. (The JPEG algforithm does not know which pixels carry true initial image data, and which carry non-image compression artifacts.) This is just one of several reasons why JPEG is called a "lossy" algorithm.

 

I'd actually call JPEG an "progressively lossy" algorithm, since the above problem also occurs when you repeatedly open and close/save a JPEG that you are processing and manipulating. This is why using a TIFF version is always a good idea if you plan to process the image to any extent.

 

Last week, I had the pleasure of helping a former college professor who had ruined a JPEG photo related to one of his papers. He ruined it by repeatedly opening and closing/saving it (many, many, many times)...as he referred to it while writing his paper. By the time I saw the image, he wondered why it had started to look like a checkerboard. It even had horizontal lines running all the way through it!

 

His was an extreme case, made worse by two things:

 

* He was saving it every time, rather than just closing it.

 

* He was not even saving it each time at the highest JPEG quality setting (which accelerated the damage).

 

I was his lab assistant back in 1969 (taught astromomy/cosmology). And I took on that mantle again last week to "fix" his image problem. Wasn't hard, though, since the original file was still in his digital camera. I guess once a lab assistant, ALWAYS a lab assistant!

[jcuknz]

Answering from slightly different tack my understanding is that the computer on opening jpg file in it's editing programme is treating it at 'normal' size rather than the compressed size on the camera storage card.

 

What the programme reads out in the line above the picture, ie. dog.jpg doesn't mean that it is a jpg file but rather that is where the info came from. As repeatedly suggested above if you simply click the 'save' icon it will use the jpg compression process to make a 'nice' small jpg file again of the picture.

 

But the fact that it continues to read 'dog.jpg' through a complicated editing process merely means that that is where it came from and has nothing to do with, or any effect on, the editing process.

 

My system......

When I return to the computer I use Windows Explorer [W2K or XP] to first EDIT > SELECT ALL > COPY all the files to my archive folder.[i'm using a card reader but the USB cord connection to camera works the same, an external file source] I then use EDIT > SELECT nnn > MOVE to shift the files into working folderby subject matter. My camera card is now empty and ready to be used again. CF cards seem to store up a small amount of junk which hasn't bothered me yet becuase I don't take that many photos. While my SD cards are not showing this accumulation as I detect it, reading the file content of the 'empty' card in Properties after each download.

 

Once I have done some editing of a file I save it as pspimage or psd and not a jpg. But if you want the file to be read outside of your computer it is a good idea to make a Tif version. Tif has been around for ages and some suggest it will still be around when the likes of pspimage and psd are just fond memories ... so it is the obvious choice for archiving edited files.

[Landrum Kelly]

I know that Ilkka is right, but I cannot escape the compulsion to convert all of the RAW files to TIFFs right out of my Kodak 14n. If I am serious with my Olympus E-20, I save as TIFFs in the camera, although that is terribly time consuming and best suited for landscapes or other things that are not going to be moving right away.

 

My procedure of converting all RAW files to TIFFs did result in my having to buy a new computer system, being sure that it would handle twin hard drives. I opted for the Dell Optiplex system. On my earlier Dell system, I filled up the disk so fast that I very quickly had to buy a big external hard drive.

 

In spite of those errors, I am glad that I proceeded as I did. I now have the storage and computing speed to handle all of the images out of these two cameras. We shall see what it does with my 4x5 scans on my Epson 4990 scanner, both still sitting virtually unused after a chaotic year in a new teaching job.

 

In any case, since the price of storage media is dropping, I think that saving or converting to TIFFs is the way to go. When I am manipulating, I save after each new operation with a new file name that tells me what the operation was. My own system is to use "bri" and "con" to stand for brightness and contrast, respectively, each followed by the numerical value of the adjustment. I likewise put "sat" followed by the numerical value for the saturation increase or decrease, as well as "usm" and the numerical value for the sharpening that I do with Unsharp Mask. Everyone uses his or her own "code," but the point is not only to save many LOSSLESS data files, but to keep a record as to what one has done, in case one decides at some point that one should have taken another fork in the road about three steps back or so.

 

Everyone works with what they have available. I still like to purge obviously poor TIFFs pretty quickly, as I find them, but at the stage of hooking up the camera to the computer, I just run the software that automatically converts RAW to TIFF--and then I go do something else while the conversion is running.

 

I keep the RAWs just in case. Maybe my procedures are overkill, but I rarely lose a good file out of the camera. In fact, I can't remember the last time that I did, and lossless processing is definitely the way to go if you do a lot of manipulations.

 

Nothing is so frustrating to me as to find that I have been manipulating and repeatedly saving a JPEG--especially if I did not keep the original file, and the file is now reduced to a skeleton of what it once was. Come print time, that loss will show a lot faster than it will on an interlaced computer monitor.

 

Therefore I will keep either shooting TIFFs in the camera or converting to them as my first step out of camera--depending on the camera. You never know when you are going to get a keeper that you wish that you had gotten or saved as a lossless file.

 

--Lannie