Is constraining necessary before printing?

Question

I have several related questions as I just discoverd this constraining feature:
(1) It appears as though the constrain function is just showing me how the photo will look if I choose to print it in that size, but it doesn't actually change anything, right?
(2) If I don't constrain or crop a photo, but I instruct the developer (Apple or Kodak) to print a 4x6 size, what will be the outcome (i.e. will my photo look different than it appeared when I downloaded it into IPhoto)?
(3) I'm a beginner, so I assumed that if I crop a photo, then that is exactly how it will print out no matter which print size I specify - is that correct?
Thanks much for any advice you may have!
iBook G4   Mac OS X (10.4.8)  

Answer 1

I'm a beginner, so I assumed that if I crop a photo, then that is exactly how it will print out no matter which print size I specify - is that correct?<<<</div>
Absolutely no.
If I don't constrain or crop a photo, but I instruct the developer (Apple or Kodak) to print a 4x6 size, what will be the outcome (i.e. will my photo look different than it appeared when I downloaded it into IPhoto)?<<<</div>
It WILL look different. The print shop will simply do its best.
It's probably easier if I give you a mini-education. This is a problem that has existed since the days of Matthew Brady but we are now more cognizant of it. In the old days, you never noticed that the printed picture didn't match the film image perfectly.
Every photo has an aspect ratio, which is nothing more than width by height. The 2X3 ratio is the norm with 35mm film cameras and it results from the fact that the image on the film is 24mm high by 36mm wide. (That's approximately 1 inch high by 1.5 inch wide.)
I can take an exposed negative and make a "contact print" that will be exactly the same size as the image on the film. I can also enlarge that image and make a print that is 2" X 3" or 4" X 6" or 8" X 12". You'll notice that each of these prints retains the 2:3 aspect ratio because, to avoid distortion, I must enlarge the height the same that I enlarge the width.
The problem now is finding paper to print on. There is no 2" X 3" paper. If you want a 2" X 3" print, you'll need to print on 4X6 paper (or larger) and then you'll simply cut off the white space and end up with a 2X3 piece of paper. No problem except for wasted paper.
If you want a 4" X 6" print, it's not problem. The paper is readily available.
The real issue with the 2X3 ratio is with 8" X 12" prints. That size paper does exist but it's hard to get and generally you'll need to pay a premium price to get the printing done at a professional lab. Most persons will compromise and make an 8X10 print. This is actually an 8X12 print with two inches of the image cut off (cropped).
Digital cameras typically produce images with a 3X4 aspect ratio and there is NO paper commercially available at that ratio. Cropping is ALWAYS necessary. My camera allows me to limit my images to 2X3 and, for me, that simplifies the matter greatly. Most of my prints are 4X6 and, even for those that are not, I have many years of 35mm experience and I'm used to that ratio.
One way to keep all the above in mind is to consider a square image with paper that is not square.