pixel size

[FrankS]

I’m going to be photographing photos for a doctor for his brochure, I’m going to use my new Canon 80D that has 0.3- 2.5- 5.9- 11- 24 megapixels the question is what would be a good pixel size? Would  5.9mp or 11mp be good size? The photos size in the brochure would be from 2X2 to 2X4.

Thanks

[Waddizzle]

Shoot the photos at the maximum resolution that the camera can capture.  You can always reduce the resolution of an output file for publication, but you cannot increase it beyond what was originally captured.

[RobertTheFat]

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@Waddizzle wrote:

Shoot the photos at the maximum resolution that the camera can capture.  You can always reduce the resolution of an output file for publication, but you cannot increase it beyond what was originally captured.

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And shoot in RAW mode. Commercial printing can be pretty unforgiving, and do-overs are expensive. Give yourself every opportunity to get it right.

[ebiggs1]

One of the things that can be the hardest to get your head around is resolution. Confusion is compounded by the fact that there are two different kinds of resolution. One is dots per inch, and the other is pixels per inch.

1. Dots per inch (dpi). This refers to the number of dots per inch that an inkjet printer is capable of applying to a sheet of paper. It can range from 720 to 2800 and more. The closer these dots are to each other, the more they blend together forming continuous tones on the print. The only time to discuss dpi is when you are talking about a printer.
2. Pixels per inch (ppi). This is the resolution used in digital photography. It is the distance between the pixels that make up digital images. Pixels per inch is important because it determines what digital images look like when they’re displayed and printed. 

These two terms are mostly not understood by most people.  If I were you I would, and I do, shoot at the best the camera can do and in RAW format.

[TCampbell]

You have a choice of having the camera save the images as either JPEG format or RAW (or both).  JPEG is great for images that you plan to shoot & share immediately without doing any adjustments to them.  If you do plan to adjust them (and most of us do) then RAW is better ... and for several reasons.

One of the benefits of JPEG is that it tends to be extremely good at reducing file size.  But this doesn't come without a consequence.  In order to reduce the filesize, the JPEG algorithm analyzes pixels and compares nearby pixels for subtle differences in hue and brightness.  If it thinks the difference is too subtle for a human eye to notice, then it "normalizes" the pixels so that they are identical in hue & brightness because this allows better compression (for storage) and the feeling is that you probably wont notice the loss of data anyway.

HOWEVER... if you do plan to adjust the images (exposure, contrast, white balance, etc. ... but in particular, the ability to recover details in shadows or highlights) then the problem with JPEG is that it would have altered the data to normalize the pixels (for compression efficiency) and now there is longer any detail that can be recovered.  But had the camera used RAW format then the post processing software on the computer could have recovered quite a substantial amount of detail.

That's why most of us shoot RAW.... you can do so much more with the image after it's captured.  

You do need to have software that can deal with the RAW photos.  Canon's Digital Photo Professional came with your camera.  Adobe Lightroom is popular (but that's only available by "subscription").  On the low-cost side, Adobe's Photoshop Elements is rather inexpensive and it can deal with RAW files.  I don't use GIMP, but GIMP is free and I think even GIMP can now deal with RAW files (it used to be JPEG only).  All of these programs allow you to either crop or resize the image to fit the space on your printed brochures.

There are some basic photo adjustment programs that really only deal with JPEG and you have to be careful because some of these can "read" the RAW file, but they immediately create a JPEG version and then all edits are done in JPEG format (which is not the same as having software that can deal with it exclusively in RAW mode and then you only do a JPEG conversion on the final version of the image that you plan to print.