Lossless compression. TIF.

[David Metsky]

I am concerned as to how well my images will come out on the printed page. I can batch convert all my jpegs to TIFF but doubt that that will improve the image quality in the book.

They'll be fine, you have nothing to worry about. Converting to TIFF won't help you at all. There's no point, you can't save information you don't have. And as long as you preserve the original JPGs your images will be as good as possible.

-dave-

 

[DougPaul]

OK, here's the practical reason behind my question. I'm working on a guidebook and am taking pictures to put in it. I was told by a guidebook author to save my work in TIFF. I'm using a 6 Megapixel Canon A540 which I now know only saves in JPEG mode, neither RAW nor TIFF. I am concerned as to how well my images will come out on the printed page. I can batch convert all my jpegs to TIFF but doubt that that will improve the image quality in the book.

See if you can find a pro photographer who has published photos or an editor to ask.

FWIW, the pics in some of my technical climbing guidebooks aren't all that great. It probably also depends on the purpose--the climbing guidebooks just want to show the routes. If you are trying to show some nice scenes printed on glossy pages, the standards would probably be much higher.

Dave is correct--converting to TIFF will not improve the images. But it might be a preferred format of publishers. (Another question to ask...)

Doug

 

[forestgnome]

Thanks for a very educational thread

I sell nature photgraphy in prints up to 12x18; always wondering how to improve but technologically challenged

I shoot with a Canon Digital Rebel (6.3 mp). I usually shoot in the next step down from RAW because I don't know how to deal with the RAW image. It doesn't show up on the camera screen after the shot, and I can't fugure out how to bring it up on the computer screen.

Any help would be greatly appreciated. I'm really excited for the autumn

 

[Tom Rankin]

Thanks for a very educational thread

I sell nature photgraphy in prints up to 12x18; always wondering how to improve but technologically challenged

I shoot with a Canon Digital Rebel (6.3 mp). I usually shoot in the next step down from RAW because I don't know how to deal with the RAW image. It doesn't show up on the camera screen after the shot, and I can't fugure out how to bring it up on the computer screen.

Any help would be greatly appreciated. I'm really excited for the autumn

I have the same camera. When I shoot RAW, I can see the image on the screen, both just after the shot and reviewing it later.

If you want to process RAW images, you can use the free software that came with the camera. It does take a little practice, but for you it might be worth it. There are other threads on processing raw images. MichaelJ gave me some good tips on using it a while back. "Seek and ye shall find"!

 

[nartreb]

They'll be fine, you have nothing to worry about. Converting to TIFF won't help you at all. There's no point, you can't save information you don't have. And as long as you preserve the original JPGs your images will be as good as possible.

-dave-

Dave is quite right. It's harmless to convert to TIF if it makes your author happy, but it's not necessary for any technical reason.

I've got a three-foot-tall print from a 7-megapixel Canon A620 (which only saves as JPEG) hanging on the wall beside me right now, so I think a JPEG from an A520 will be just fine for any guidebook I'd want to carry.

I shoot with a Canon Digital Rebel (6.3 mp).

the Rebel will not shoot RAW in full-auto mode, or any other mode in the "Basic Zone". But that should just mean you're shooting in JPEG, not that your screen goes blank... PS nice avatar!

 

[SAR-EMT40]

Run-length-encoding isn't of much use for photographs... OK for digitally drawn sketches, though. Digital drawings fill large areas with digitally constant colors--photos have variation on all distance scales.Doug

Yep. But it is killer on line drawings and other bi level type images. It actually can do well on pictures/drawings that are 2 or 3 bits color depth with a lookup table. Like the early paint images.

Ah yes, Hamming code. Brings a tear to my eye.

As far as converting to TIFF. Like everyone is saying. You can transfer it to TIFF with no more loss of detail than you started with if it is a JPEG. It obviously isn't going to "heal" the image from the "damage" done by the JPEG encoder though. If that is what they want go ahead. Of course if they plan on making the image larger than what you are looking at it you may start to see some artifacts. Smaller image - crisper looking image : Larger image - more chance artifacts from JPEG compression might be spotted.

And as long as you preserve the original JPGs your images will be as good as possible. -dave-

Very well stated and diplomatic Dave. As good as possible. Not as good as it could be.


Keith

 

[Neil]

Smaller image - crisper looking image : Larger image - more chance artifacts from JPEG compression might be spotted.

That statement reminds me of something else i need clearing up on:

I believe that making a jpeg smaller is achieved by removing pixels (that are lost forevermore if you don't do a "save as"). I previously thought that the image was made smaller by shrinking and scrunching all the pixels into a smaller space. Am I right now or was I right previously?

 

[nartreb]

The very short answer is that what you now believe is basically right.

The long answer was getting very long - all about details of the JPEG format, and dots per inch, and situations where the size info in a JPEG file gets ignored anyway, and a reminder that this kind of size is totally different than the "file size" we've been talking about earlier in this thread (which refers to memory used, not appearance).

What will happen, in practice, when you use an image editor to make an image file appear smaller ("scale the image"), is that details that are now too small to see will get thrown out (once you save your changes). This is easy to demonstrate: the new file will use far fewer bytes of memory {there's "file size" again} than the original. The only way that can happen (since they're both using the same compression scheme) is if information was sacrificed. Of course, you shouldn't care because all you lost was stuff you can't see anymore, and if you've followed our advice you've still got a copy of the original in case you ever want to see it large again.

By the way, you'll get a little bit of degradation by making a JPEG larger too, just because of the way JPEG compression works. Not something that most people need to worry about.

I'm almost certain that size information (and dots-per-inch) is in a header section of the JPEG file that's separate from the compressed stuff. So an advanced editor might let you mess with those numbers without trying to re-compress the file. [Edit after some more research: I think messing with the height or width (which are recorded in pixels) without re-compressing risks making your file unreadable, but changing the dots-per-inch number might be OK.] But there's not much point in that anyway: most viewing and printing software can display an image at any width that you specify.

 

[w7xman]

Thanks for a very educational thread

I sell nature photgraphy in prints up to 12x18; always wondering how to improve but technologically challenged

I shoot with a Canon Digital Rebel (6.3 mp). I usually shoot in the next step down from RAW because I don't know how to deal with the RAW image. It doesn't show up on the camera screen after the shot, and I can't fugure out how to bring it up on the computer screen.

Any help would be greatly appreciated. I'm really excited for the autumn

Forestnome...

I enjoy your pics and would be happy to help you decifer RAW conversion some evening before autumn...it's not that scary, but it's a big jump in post processing time...and image quality!

I have a rough schedule, but we can iron something out I'm sure if your up for it... Offer really up for anyone...PM me...

 

[DougPaul]

I believe that making a jpeg smaller is achieved by removing pixels (that are lost forevermore if you don't do a "save as"). I previously thought that the image was made smaller by shrinking and scrunching all the pixels into a smaller space. Am I right now or was I right previously?

The best algorithms use interpolation. Simply dropping pixels (for downsampling) and copying pixels (for upsampling) will yield inferior results unless the picture is way oversampled (far more samples per inch than necessary).

You start with the picture sampled on the input lattice and want to resample it on a different output lattice (with more or fewer points). You then use interpolation techniques (ie predict the value of an output lattice point from the values on nearby input lattice points) to give you values for the output points. For some interpolation algorithms, if an output point is at the same location as an input point, you just copy the value.

Simple cases are up and down sampling by factors of small integers. (2 is particularly easy.)

Whenever you have an insufficient number of samples per inch (either by an initial insufficient sampling or by downsampling too much), you can get aliasing--a form of information loss. For instance, take a picture of an evenly spaced picket fence. When you have a small number of pixels per fence posts, you can get beating patterns (auditory term) or morie patterns (visual term)--these are forms of aliasing. It can also show up as other kinds of artifacts.

Aliasing is a standard issue in signal processing. Any time that you do not sample a signal (eg image) often enough, you can get aliasing. There are theorems (the Nyquist limit) about how often you need to sample to avoid aliasing.

Doug
who majored in signal processing