... What about reducing file sizes...?

[kevinbriggs]

<p>There have been many threads within these forums on the subject of enlarging digital files (whether within Adobe Photoshop, Genuine Fractals, Qimage, etc.).</p>

<p>But what about rules/tactics for digital file reduction...?<br /><br />For example, at 240 PPI, the Canon 1Ds Mark III I'm using makes files that are just about 16" x 24" (just a little bit smaller than this). If I want to make a stunning print at 12" x 18", do I simply use Photoshop's reduction options, or do I go with a third-party program...?<br /><br />What's the best method for reduction...?</p>

[Larry_G1664882113]

<p> The "image size" box in the Image menu of Photoshop has a pull-down bar at the bottom where you can choose the option for best reduction. I hope this gets to your question.</p>

[kevinbriggs]

<blockquote>

<p>The "image size" box in the Image menu of Photoshop has a pull-down bar at the bottom where you can choose the option for best reduction. I hope this gets to your question.</p>

 

</blockquote>

<p>Hi Larry,<br /><br />Yes, I've tried that process before (hundreds of times). I'm just wondering if it's the best process...?<br /><br />Or is there some other process and/or piece of software that someone would recommend for a better final product...?<br /><br />Thanks!</p>

[marc_rochkind]

You have to experiment. There are at least 3 choices:

 

1. Leave the image alone and let the driver/printer deal with the surplus of pixels.

 

2. Change image size but do not resample. PPI will increase.

 

3. Change image size and downsample to keep PPi less than some magic number (e.g., 480) that depends on

driver/printer/paper.

 

The choice also depends on whether and how you are doing output sharpening.

 

My guess is that #2 is best unless the PPI gets unreasonably large.

 

--Marc

[kevinbriggs]

<p>Thanks for the info Marc!</p>

[jacopo_brembati]

<p>If you have to downsize an antialising filter have to be used.<br /> Strong downsizing (without a good antialiasing filter) generates strong artifacts.<br /> Adobe downsizing algorithms are not very good.</p>

[mendel_leisk]

<p>If you're doing your own printing, ie: are not concerned regarding emailing of excessively large files, I don't see that there's any reason to reduce your images dimensions, the pixel dimensions, to print small.</p>

<p>You start a print job tell the program you want it to fit a certain paper format, it adjusts the dpi (typically upwards) to suit. Am I missing something? Is this method going to be at a disadvantage in some way, compared to a print from a downsampled file?</p>