When I first started out in photography I thought all i needed was one good bag. So I was in search for an all in one. Keep in mind at that time, I did not do studio photography. I concentrated mainly on landscape/outdoor photography. That is where you start in photography when lights are not apart of the arsenal. With that in mind, I searched for a light and easy to access camera bag. My search led me to the Lowepro Topload Zoom AW.
As I grew more into photography in terms of photography style, I required more and more space. I started to bring my laptop to my Los angeles photo shoots. I also purchased my first speed-light the Nikon SB600. Therefore, I went back to the camera store and searched for a bag that can house my laptop and photography equipment. I then found the LowePro CompuTrekker AW. 
This backpack allowed me to carry my photography equipment and laptop at the same time. Note that if you have a 15.4 Macbook pro with a clear hard-shell case, the space will be a little tight. If you have a 10 inch netbook, It should be a perfect fit.
Ok now a few months pass and I need to travel and require a bag that can carry my clothes and camera gear. So through further research and guidance from experienced photographers, I found the Think Tank Photo Airport Security V2.0. 
This bag allowed me to go through the airport worry free and go through all of Security without hassle. Make sure to look out for the equipment reviews for all of the products mentioned soon.
In Conclusion, one bag isn’t enough. Buy a bag for each purpose and your workflow and organization abilities will surly improve and make your photo shoot a little more efficient.
I am a Southern California based photographer concentrating on
Advertising/Commercial Photography and Wedding Photography. MISSION: Produce
highly conceptual and relevant images that translates to high message
recall for my clients. PHILOSOPHY:
An image captured is a memory recorded so make sure it's done right. STYLE: EDGY Point of
View. MeTHod To mY
MaDNEss: Plan, plan, and plan. Basicaly, I am a HIGHLY
CONCEPTUAL photographer that produces EDGY POV images with high message
recall because of the intense planning/research involved to create each
image. You may follow me on twitter