"Optimum" enlargement size?

[Randy H]

I realize most shooters using 8x10 or 11x14 do mostly contact printing. Shooting 5x7, I have no issue at all enlarging to 8x10 or 11x14. Haven''t tried anything larger. Now the question:
Is there an "optimal" size consideration for different formats? I have a 3.25x4.25 and a recently acquired 4x5. Having not done any enlargements with either of these, is there a point where quality starts to denegrate? And if so, where?

[Lazybones]

West Coast Imaging (http://www.westcoastimaging.com/wci/page/info/articles/formatsize.html) has a chart. I'm not sure how conservative it is though, and how much film speed and/or grain effects a given size.

[Michael Graves]

Optimum print size depends on both viewing distance and subject matter. If you enlarge a perfectly sharp negative 20x and try to view it from the tip of your nose, you'll complain about the quality. Hang that same 20x24 from the 35mm neg on the wall and look at it from ten feet away and it might look gorgeous.

As far as subject matter goes, I always had a hard time with 30x40 enlargements of closeup images of bugs. Those things are ugly enough when they're little. When they're that big, they're TERRIFYING!

[Oren Grad]

There is no objective answer - this is a matter of personal taste.