Originally Answered: What do I need to know for the photoshop cs5 ACA exam?
I am not sure if my answer will be of much help since I think your Ps visual communications for ACA might be different from the Ps proficiency i take for ACE, but i guess they share very similar traits so i'll give you some tips based on my experience.
You will be taking Ps CS5 certification so understand well what are the new features and functions that were not present in the previous CS's. Study hard on all of them. There are several questions about the regular operations but you will be bombed with questions about the new features-- this is what is regularly updated in the exams and is the big difference between a CS4 certification and a CS5 certification.
Be very aware of functions and operations that are not allowed when in certain modes. An example would be to open a file in your Ps and change from one image mode to another. You will notice several functions that are available in some modes will be grayed out in other modes.
Be very aware of differences in defaults. When i mean differences, i mean in how they are handled. An example would be opening a png file is quite different from the others-- a png by default opens as a layer while others such as jpegs, tiffs, and bitmaps open as backgrounds.
Finally, it would strongly help if you can operate Ps blindfolded-- i mean that almost literally. If you know the program functions and steps enough that you can actually instruct someone over the phone without Ps in front of you and the output of the person on the other end of the phone will be very much as you know it would, you will be on solid ground. I mentioned this because it would help a great deal if you can visualize your workspace and the actions to be done (like doing photoshop in your head) as you are taking the exam because Ps won't be in your reach while at it, not to mention you won't have much time to think-- you will, on average, have barely a minute for each question so you definitely have to be very familiar with it to think fast. Don't stay too long in one question... It's multiple choice so if a question stops you like a wall, give it your best guess and move on to the next.
When i took my exam for my first certification, the test was quick, rigorous but not difficult and definitely not what I expected. The test does not ask you to manipulate any images nor would there be any essays for explanations on design-- it is all about the operation of the program. As you see from the tips I gave you, you will notice that even if you are very familiar with the program and have been using it for a long time, there are actually several questions which are so minor you don't need to know them by memory but is still expected that you do. I have been in the creative industry for several years, I use the Creative Suite just like another set of hands, and yet I was still caught off-guard with those kinds of questions. I guess i just find those questions annoying.
Anyway, hope I was able to give a bit of useful advice. Don't worry too much about it, you'll eventually get used to taking the exams-- you'll want to take it again when CS6 comes out to stay updated. If topics that i mentioned such as image modes are not in your study guide, then i guess it won't be in your exam, but i still would suggest to at least go through them coz you never know... I am putting a very good bet on the CS5 new features/functions part though. Good luck in your certification! :)