# Tiff...Jpeg...8 bit...16 bit...PPI....HELP!!!



## MisplacedAngler (Oct 5, 2010)

I've done some searching on the internet and throughout TPF so I've gained some basic knowledge.  I would like some advice on what experienced people think I should be doing to achieve what I want.  Pretty much I've been doing HDR with 3 shots and processing the raw photos directly into photomatix.  After that, I save as jpeg, then I load into gimp and make other minor changes.  I now have a few pictures that I really like and want to print off in large format and, obviously, I want them to look as good as possible.

What format should I do processing in...8 bit or 16 bit...tiff of jpeg?  I think I'm going to try mpix so that pretty much narrows down my end product to 8 bit jpeg.

How many PPI do I need for a large print? 
I've read 300+ but I've also read for larger prints 200+ works fine.  I can print 12 x 18 at about ~240 ppi and I think this size works good for what I want, but if it's going to be poor quality I'd rather go 8 x 12 or 10 x 15 or something.

I've prolly got 1,000 other similar questions but they're all on this track....so wise one's of TPF, impart some of your knowledge on me.


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## epatsellis (Oct 5, 2010)

16 bit tiff until the final image, then if need be, jpg.


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## Garbz (Oct 6, 2010)

The bitdepth for the final image isn't important, only the processing is. For that 16bit or bust. Check out this current thread: http://www.thephotoforum.com/forum/...nvert-8bit-16bit-before-editing-new-post.html

As for PPI, how big is big? PPI is Pixels Per Inch. The number 300 assumes you'll be looking at the picture from up close sticking your nose into it. I have a 40" wide picture on the wall and I don't think anyone's ever come closer than 1m from it when looking at it. 150ppi or less would have been fine for that image.


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## MisplacedAngler (Oct 6, 2010)

Garbz said:


> The bitdepth for the final image isn't important, only the processing is. For that 16bit or bust. Check out this current thread: http://www.thephotoforum.com/forum/...nvert-8bit-16bit-before-editing-new-post.html
> 
> As for PPI, how big is big? PPI is Pixels Per Inch. The number 300 assumes you'll be looking at the picture from up close sticking your nose into it. I have a 40" wide picture on the wall and I don't think anyone's ever come closer than 1m from it when looking at it. 150ppi or less would have been fine for that image.


 
By big I was looking at 12 x 18.  Nothing like 40".  I've got a standard 12.3mp camera so that's ~240 PPI at 12 x 18 or ~180 PPI at 16 x 24.  Would 180 PPI look good at that size?  I realize there is no need for one to get their nose right up to it at that size, but I have no experience with this at all.  All the help is much appreciated.


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## skieur (Oct 6, 2010)

It depends on the viewing distance. High locations or behind furniture means that you will not be looking at it up close and fewer dpi or ppi will work but if you can look at it very close 250 plus dpi or ppi would be very advantageous.

72 dpi. is the default starting point for most cameras and screen resolution, but you can adjust from there.

skieur


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## KmH (Oct 6, 2010)

In the interest of accuracy, dpi and ppi are not the same thing and are not interchangeable terms.

Neither DSLR cameras nor screens display dots (dpi = dots-per-inch), they do ppi, and most digital display screens today are 90-100 ppi.

Screen ppi does not mean the same ppi as a camera image, unless the image is displayed at 100% (1 image pixel = 1 screen pixel). If you have a 3264 pixel by 2456 pixel image, the entire image, at 100%, will not fit on a 1024 pixel x 768 pixel monitor.

The minimum ppi an image needs to be printed at is largely dependent on the quality of the image.

Mpix will not risk their reputation on photos at less than 100 ppi. Also you need to be sure your photo is in the sRGB color space but _does not_ have an embedded color profile. Mpix's chromogenic printers output at 250 ppi. A chromogenic print is made by exposing light sensitive paper with the image, then applying a chemical development process (usually RA-4 chemistry today) to the paper.

JPEGs can only have an 8-bit depth.


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## MisplacedAngler (Oct 6, 2010)

KmH said:


> Mpix will not risk their reputation on photos at less than 100 ppi. Also you need to be sure your photo is in the sRGB color space but _does not_ have an embedded color profile. Mpix's chromogenic printers output at 250 ppi. A chromogenic print is made by exposing light sensitive paper with the image, then applying a chemical development process (usually RA-4 chemistry today).
> 
> JPEGs can only have an 8-bit depth.


 
1) What is an embedded color profile?

2) How do I know if I have an embedded color profile?  I don't really know what that means so I'm pretty sure I didn't put one in my photo.  Would photomatix or gimp have put an embedded color profile into my picture for me.


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## ann (Oct 6, 2010)

you can control the color profile in camera. Most cameras have a default of sRGB, but can be changed to Adobe RGB or Adobe 1998

Some software; ie. photoshop being one can can that color space


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## Garbz (Oct 7, 2010)

For the love of god leave colour profiles as something to investigate next year. If you see an option that says "sRGB" then tick that 

If in Photoshop the save dialogue has a checkbox that says embed colour profile, untick it. Colour profiles are a world of hurt when you're first starting out.


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## GeneralBenson (Oct 7, 2010)

Garbz said:


> For the love of god leave colour profiles as something to investigate next year. If you see an option that says "sRGB" then tick that
> 
> If in Photoshop the save dialogue has a checkbox that says embed colour profile, untick it. Colour profiles are a world of hurt when you're first starting out.



Hahaha. So true!


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## ann (Oct 7, 2010)

altho i responsed or tried to as simply as possible ; Garbz suggestion is the best and gets double thumbs up


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