Why don't we get hot pixels while using live view mode, but do get then on a long exposure? I read somewhere that they appear due to the sensor being activated for too much time, but then, live view should also show them.
On a long exposure charge is allowed to accumulate on the sensor over a period of time, whereas in live view the sensor is discharged for every frame (so thirty times a second or so). Some hot pixels result from slow charge leakage which only occurs during a long exposure, hence you wouldn't expect to see these in live view.
Also liveview subsamples the sensor so you dont see every pixel.
+1 - Learn something new every day. Didn't realize LV subsampled. Upon thinking about it, it would really have to - just didn't realize.– rfuscaJul 25, 2011 at 15:05
1Question is - does it subsample when viewing 10x zoom in??– ysapJul 25, 2011 at 15:12
@ysap As far as I know there's always some form of sampling/interpolation going on - you never get a 1:1 correspondence between sensor and LCD pixels. 10x magnification is the same size regardless of how many megapixels you have so there must be some scaling going on! Jul 25, 2011 at 15:30
2Ok, running some numbers, I believe the LCD screen on a 5D is 640 by 480. It's marketed as 920,000 "dots" but they count the red/green/blue subpixels as separate dots, thus 640 x 480 x 3 = 921,600 the sensor resolution is about 5616 x 3744 (give or take some masked pixels) so at 10x magnification you're looking a patch of sensels measuring 562 x 374 so it would be possible to show the sensor pixels 1:1, however given the sharpness, and the existence of cameras with less than 21MP, I think the camera subsamples, then upsamples the live view data! Jul 25, 2011 at 15:53
2it doesnt subsample to 1x liveview and then upsample to 10x. I use mostly manual lenses and 10x liveview is amazing for getting tack sharp eye lashes. If it downsamples and the upampled those details would vanish. Jan 4, 2013 at 13:24