default resolution - 5D MKII

<p>The default resolution of photos taken on my 5D MKII is 240dpi. . . is it possible to reset this to a different resolution? David</p>

<p>The default resolution of your camera is 5616 x 3744 pixels. The dpi value embedded in the file is meaningless. </p>

 

<p>Rob is right the dpi value is meaningless in terms of the resolution of the camera. This thread way on a similar topic a few days ago: <a href="/beginner-photography-questions-forum/00bXZR?unified_p=1">http://www.photo.net/beginner-photography-questions-forum/00bXZR?unified_p=1</a></p>

 

<p>Rob is right the dpi value is meaningless in terms of the resolution of the camera. This thread way on a similar topic a few days ago: <a href="/beginner-photography-questions-forum/00bXZR?unified_p=1">http://www.photo.net/beginner-photography-questions-forum/00bXZR?unified_p=1</a></p>

 

<p>I don't know if the 5d MKii has it or not, but my 7D has a medium Raw (brings it from 18mp to 10mp). </p>

<p>The 5D2 does as well, though I cannot recall the sizes (never using them ;) )...</p>

<p>It is possible to reset this 'dpi' in post, but it is meaningless unless you are printing an image, because the printer and computer chat about what that means in regards to your output - resetting this may change the quality of your output, especially if your printer driver is a bit obnoxious. </p>

David, do understand what we mean when we say the "dpi" count is arbitrary? Firstly dpi is the acronym for Dots Per Inch

which really applies only to printing, it refers to printing resolution. . The only place you see a "dpi" value is in your image

processing software and its an easily changeable setting. I don't know why they use the number 240 as a dpi

measurement: Canon and HP inkjet printers native resolution is 300 and 600dpi, Epson inkjet printers print at 360/720

dpi and my understanding is that Lightjet and Fuji machine printers work at 200 dpi.

 

Btw most LCD screens used in computer displays are 99 pixels per inch. "Retina" screens are somewhat higher. But I

digress, so back to printing.

 

What happens when you send an image file that has a resolution number smaller than the minimum (300 or 360 for the

inkjets) to the printer is that the printer internally interpolates up to 300 or 360 dpi. If the resolution of the file is higher than

300 or 360 ppi then it interpolates up to 600 or 720 dpi.

 

It is better for you to exert control and work at the resolution you'll print at. This avoids exaggerating artifacts like

sharpening halos and edge jaggies.

<p>The "DPI" embedded in the file is worse than meaningless, it is misleading, because what they really meant to embed was the value for PPI: pixels per (linear) inch (of output.)<br>

DPI is a printer measure ("how many dots of ink, vertically and horizontally, a given printer is capable to spray"), say 4800x2400 dots per linear inch. PPI means "how many pixels from the image is spread out over a linear inch of output." Two different things.</p>

<p>Somehow the DPI and PPI got mixed up and even camera manufacturers started using these terms interchangeably and these terms are NOT interchangeable. </p>

<p>For what it's worth, having had a rummage through the manual, no - I can't find any way to change the default PPI. As other people have said, it's usually irrelevant, and most sane people will decide how big they want an image to be printed rather than deciding how big it should be printed based on the number of pixels and some acceptable PPI value, and much confusion would have been avoided in Photoshop if Adobe hadn't decided to hide the concept of a pixel from people and had made the ppi fields informative rather than selectable. There's no accounting for someone with a weird workflow, though - and that person may not be the OP.<br />

<br />

Rather than being dismissive, shall we make sure that we know why David wants to change it? (Changing it in software off-camera is likely to be the least painful approach, even if it <i>is</i> buried in a menu somewhere.)</p>

As Rob pointed out, if you use the full area of the 5D Mk II's imaging sensor you have 5616 x 3744 pixels to work with.

 

To determine how that translate into print sizes you divide 5616 and 3744 by either the size in inches you want the print to

be or by the dpi number. With the Epsons and a large print you can send the printer a file with a ppi resolution value as

low as 180 and the printer does a pretty good job of interpolating the ppi resolution up to 360 dpi. With the Canon's I also

use the low ends value is closer to 225 ppi.

 

If you are printing smaller than say 10x15 you are better off keeping the ppi number high as people look at smaller prints

from a closer distance so they can take in the entire image in a glance.

 

If you are using a lab to print your work, just simply change the output resolution to the dpi number they request.

<p>Ellis - Really? You've found a printer that actually pays attention to the ppi setting in the JPEG file when printing? Every lab I've met (admittedly not many) will completely ignore the ppi setting and print the image as large as you asked them to. Every time I've used a printer, I've told it how large I want the image, and the software/driver has scaled the pixels to fit (again, ignoring the stored ppi file).<br />

<br />

You may want to keep the <i>final</i> (size you're printing the image divided by the pixel resolution) ppi reasonably high so that the pixels aren't too visible up close, potentially by making sure that you're not trying to print too large, but I've never met a print device that took the specified ppi and used it to decide how large to print the result - not least because the ppi is usually gibberish and people tend to change their mind about print size at the last minute. There are some applications that guess the default size for an image in real-world measurements by paying attention to the PPI figure, but I've never met one that didn't then let you change the size.<br />

<br />

If there are printers out there that only let you specify the print size by the JPEG's ppi, I withdraw the assertion that the ppi in the JPEG file is essentially pointless. I'll go and beat up the printer manufacturers in question, though.</p>

<p>Some printers obsess over the DPI value embedded in the image. I do some work that is passed on to a layout fellow for printing in a brochure, and he asked me to make sure the images are marked 300 dpi, because otherwise the print shop refuses to print them. These images, which I usually provide at 2000x3000 pixels, are sometimes printed as small as 3/4 inch. But nevermind the math, if the file is marked 240 dpi, the printer refuses to print because "the image resolution is too low, it won't look good, we only print 300 dpi for optimal quality".</p>

<p>Fortunately LightRoom allows you to plug in any number you want. I put in 300 and now everyone is happy.</p>

<p>I totally agree that the DPI in the file is completely meaningless, but that doesn't always mean it's irrelevant.</p>

<p>Alan: Thank you. I don't want to live on this planet any more. :-)</p>

<p>Many thanks to all of you who responded... a big help!</p>