Memory management is important to PhotoRaw; efficiently converting raw images is a very memory intensive process, and unless enough memory is available, PhotoRaw will quit.
iOS devices such as the iPhone and iPad actually have two kinds of memory:
Flash memory. Flash memory is the equivalent of disk space, and is the memory "number" quoted in sales literature. E.g., a 32G iPad has 32G of flash memory. For PhotoRaw's purposes, flash memory actually isn't very important, although it does define the total number of images that your device can hold.
RAM. RAM is far more important to PhotoRaw. The amount of free RAM available defines the size of the image that that you can import, and the size of the image you can export to JPEG. Amounts of RAM vary by device. For example, a 32G iPad has only 256 MB of RAM.
As of version 2, PhotoRaw implements virtual memory. Virtual memory allows flash memory to operate as if it was RAM. You can read more about PhotoRaw's virtual memory on the Virtual Memory page.
Telling whether you have a memory problem
It's not always easy to tell if you have a memory problem. If virtual memory is enabled, and free memory is low, Photo's import and JPEG export operations will become very slow. If virtual memory is disabled, and iOS needs additional memory to do something else, it just shuts down any apps that are running that are using a lot of memory. And PhotoRaw uses a LOT of memory, so usually it's the first to be shut down. When this occurs, there is no error message or warning; PhotoRaw will simply be stopped by iOS.
There are three situations that are sure signs of too little memory:
Import operations are very slow. If your device is running low on memory, and virtual memory is enabled, import operations may become very slow if the amount of free memory is low.
PhotoRaw quits while importing. Generally, if PhotoRaw quits while importing (that is, while the activity indicator is spinning) you have too little free memory to import the image in question. In this case, perform the steps below to free up memory, then retry.
PhotoRaw quits while exporting to JPEG. If PhotoRaw quits while exporting to JPEG, you also have a memory problem. In the JPEG export case, you can do two things. Firstly, perform the steps below to free up memory. But secondly, export a smaller JPEG image, with lower quality setting. The "Default" JPEG quality setting optimizes quality to match available memory.
Freeing up RAM
iOS 4 allows programs to run in the background. However, each of these programs uses up RAM.
There are three ways that you can halt these programs, and free up RAM:
Power the device off, and then on. This is generally the easiest way.
Remove Applications from the Recents List. This is the simplest way to quit apps without powering on and off. Double-click the home button to display the recently accessed applications. One by one, press and hold the icons shown, then tap the red circled minus button. This sends a signal to the application in question that allows it to quit. The application will be re-added to the Recents list the next time you launch it.
Force Quitting. Apple's recommended way to force an app that you want to quit is to bring the app to the foreground. Then press and hold the sleep/wake button for several seconds, until the Slide to Power Off control appears. Release the sleep/wake button and hold down the Home button for another 7-10 seconds. Your screen will flash briefly and you will return to the main iOS 4 Springboard home page with its icons. This method works for all operating systems from iPhone OS 3 forward, and is the preferred method listed in the iOS 4 documentation.