Import sequence and size of the imported slices


I am new to both this forum and ImageJ. I need to import a series of raw DNG files and is the File>import>image sequence function. I select the directory in which my raw files are stored and check the virtual stack box because my raw files come from a Pentax K-5 camera and are 15Mb big while I have only 2GB ram.
The result is a stack of small image slices of 160x120 pixels. When I open the raw file one by one ImageJ opens the slice in the right size.

I do not see any parameter to be adapted for obtaining a virtual stack of 4700x3400 pixels (+/-) slices. Could it be that image sequence creates a stack op the thumbnail images in the file? How can I correct this?

Thanks in advance,



I partly solved the issue.
Using File>Import>Image Sequence opens a series of files but it is not mentioned whether it uses DCRaw Reader is used required for importing PENTAX raw files. I tried to open all DNG files and saved them as TIFF files.
When then importing the image sequence as virtual stack I works except that it presents grayscale images. So far so good. Now trying to find out why it is not reading full RGB slices.

Also the next hurdle is taken.
The saved TIFF files are RGB pictures. Using File>Import>TIFF Virtual Stack creates a stack of 3 slices (R,G,B). The different stacks need now to be combined, I suggest to put all R slices in one stack, all G slices in another stack and all B slices in a third stack.