Question on File Format

[scorecards]

As I understand it, converting a jpg to TIF results in the interpolation of pixels that are missing from the jpg file? Is that true? If so, does it still make sense to convert to TIF if there is a chance you may be doing a lot of editing in the future.

I think the answer is that this might have made sense when I was using Elements, but with LR the original jpg would still be recoverable so perhaps there is no need for this.

A related question is, if you convert a file from jpg to TIF, and then from TIF back to jpg without intermediate editing, do you get the same image? Always keeping jpg at the highest quality.

However what happens if you do not what to go back to the original jpg in LR, but want to edit further the edits you already made. Is there now an advantage to working in TIF or DNG?

 

[Gene McCullagh]

Hi Doug!

The thing to keep in mind about any "lossy" compression format like JPEG is that repeated saves will eventually degrade the image even at the highest quality setting. If you are thinking of doing a lot of editing in Photoshop then converting to a TIFF would be advisable.

However, if all of your edits are within LR they are non-destructive so you aren't repeatedly saving out the JPEG. In that case there is no need to convert to TIFF first.

Anytime you convert formats there is some impact on the image. It may be so slight as to be unnoticeable but given a sufficient number of conversions and you will start to see artifacting. So while you technically won't have the same image if you convert from one format to another and back again; you may not be able to see any difference. It's best though to plan out your workflow and avoid unnecessary saves and conversions. That's a benefit LR gives you... non-destructive editing. You don't need to really think much about the format until it's time to export.

 

[scorecards]

Thank you for that clear reply. One follow up question. I suspect I will do a lot of editing in Photoshop or Elements. However if I edit a copy of the original there would not be any need to convert to TIF. That conversion is best if I want to edit the original. By editing copies, it is almost like editing in lightroom as the original would be preserved, i.e. non destructive.

Also does converting to DNG have an advantage even if the original was a jpg? What if the orignial was TIF.

 

[dj_paige]

However if I edit a copy of the original there would not be any need to convert to TIF. That conversion is best if I want to edit the original. By editing copies, it is almost like editing in lightroom as the original would be preserved, i.e. non destructive.

Incorrect. Making a copy does not change any pixels. Editing a .jpg and then saving the result as a .jpg causes a loss of quality, and the pixels that are saved aren't exactly the same as the edit you see on the screen. As Gene said, sometimes the quality loss is so small that you can't really see it, but it is there nonetheless (and depends on the quality setting you chose when you save a .jpg).

Converting your original to a .tif maintains all pixels exactly the way they were in the (.jpg) original, and editing and saving a .tif means that the pixels in the saved .tif match exactly what you saw when you were editing.

Lastly, the word non-destructive has several meanings. In a common-sense (non-digital photography) meaning of the word, yes, making a copy and editing that is non-destructive. However, this is not what is meant in the world of digital photo editing; in layman's terms, if you have to save the results of your edit as a separate file, this is destructive editing (and this is what Photoshop and Photoshop Elements do). Lightroom doesn't save your results as a separate file, and so is considered non-destructive. I'm sure the gurus here can give you a more detailed technical explanation if you want.

 

[scorecards]

Response to djPaige

I am not sure what I said that is incorrect. I understand and agree with everything you said. However if I am editing a copy of a jpg in photoshop, the original jpg is not changed. Only by editing the original would there be an irretrievable loss of quality.

 

[dj_paige]

You implied that editing in Photoshop Elements or Photoshop is non-destructive if you work on a copy. That's not the normal usage of the term in digital photography. Photoshop and Photoshop Elements are "destructive" (and I hate that term) editors, regardless of whether you work on a copy or on an original.

 

[scorecards]

OK you are correct. It is destructive with regards to the copy, but my original would still be available in Lightroom.