Phiewer can display most of  the common RAW camera image formats:
.3fr, .ari, .arw, .bay, .crw, .cr2 ,cap, .dcs, .dcr, .dng, .drf, .eip, .erf, .fff, .iiq, .k25, .kdc, .mef, .mos, .mrw, .nef, .nrw, .obm, .orf, .pef, .ptx, .pxn, .r3d, .raf, .raw, .rwl, .rw2, .rwz, .sr2, .srf, .srw, .x3f

Images can be displayed directly from your cameras sd-card for example. Each image will be imported into Phiewer when it gets selected. As long as Phiewer stays opened the imported RAW image files are cached internally. This means you can browse them like normal image files without processing them everytime. Even if your RAW photos are a hundreds of MB, Phiewer handles them superfast to browse through with all possible actions like rotating, zooming and dragging.

Open a RAW image first imports it:

After importing RAW images, files can be viewed like “normal” small image files: