Photographic-based images bog down your computer because they are such huge, memory-intensive files. One of the things I will do before working with the photos is create a high-resolution version and stick it in a folder called, "high res". I will save it into that folder and then create another folder called, "lo-res". I save the image with the same name in each folder but reduce the image size substantially in the "lo-res" folder. I use the lo-res version while designing the graphics and when I send it to the printer for production I only send the hi-res version. Because the file has the same name, the hi-res files link for the printer. This way I am not slowed-down working on my files. Sometimes I will have to use the same file over and over in a design which can make the files enormous in size.
For example, I designed the NHL Stadium Series game at Yankee Stadium using a base of vector graphics with Photoshop (raster) brush-effects and light-effects over the vector art. I do not embed the linked images therefore I have to remember to send the linked raster images to the production team.
I have also learned over the years that if you scan an image at a very-high resolution and then reduce the resolution down, the file keeps most of it's information and clarity as opposed to scanning in at a lower resolution. I tend to work with images at 100 dpi at full-scale. I have to do some calculations when working with files to figure out what resolution will work. I like photos shot from a camera on the "raw" setting but it's rare I actually get images like that. My 100 dpi rule applies to raster images that will be seen within feet of the image. If it is a building graphic or seen from a distance than the raster/bitmap image can be as low as 25 dpi. Some billboard graphics are as low as 9 dpi and work just fine.
When creating stadium graphics it's difficult to use a full raster layout, for example, creating a field wall wrap which is a long horizontal treatment, I have to create overlapping panels for an easier installation. I will use an image of a football player, for example as a panel break with an overlap. Color is a huge issue as well. I can not control the color of a raster images in the printing process like I can with a PMS (Pantone Matching System) colored vector graphic.
As I said before, I use Abobe Illustrator with a CAD plug-in called CAD Tools to created scaled drawings used for production. The raster effects I place and link to my vector graphics add complexity and time to the files but they can add so much more depth. I can achieve looks I can't create in Abobe Illustrator. I can not build 475 foot long, 1/4" scale stadium field wall in Photoshop. The software is not set up for this niche sector of graphic design. When I do use raster effects such as glows and drop shadows I must create them for the full scale image. The effects may look good on your computer screen at 1/8" scale but when blown up on a 20-story building they may not have scaled correctly or look completely fuzzy. This is why I will take a "sliver" of an image and print it full-scaled on our office plotter to see if the effect is working as intended and the resolution is good. These stadium and building graphics cost thousands of dollars to produce and install. Testing is essential to success. A small imperfection on large-scaled stadium graphics can be a glaring error. Something that is a blip on your computer screen can be 5 feet tall on the side of a stadium when produced at full-scale.