12-14-08 - Sunday Randoms

My iPods have been locked into certain songs sets for a while now because I just don't want to run iTunes. I moved the location of my mp3 dir a while ago when I got the HTPC, and iTunes is pointing at all the old stuff. There are some hacks around the net about ways to move the dir without reimporting everything, but I tried some and it didn't work, so I just gave up and deleted the iTunes database and am reimporting everything. I'm currently about 30 hours in to the import; it seems near done now...

Having iTunes running and slowing the machine down to a crawl lets you see weird bugs in Explorer. For example, when Explorer redraws the desktop, it actually redraws the whole thing top-left justified with no task bar. Then if your task bar happens to be in the top left, it clears the screen, draws the taskbar, and redraws the icons shifted over by the task bar amount. That is some crazy shitty programming and the kind of thing I always try to be careful about in games. It's a good trick in game development to test your game at 5 fps so that you can see all the one-frame glitches. People often have one-frame bugs in the whole input->action->rendering chain.

It snowed a lot last night. It's bitter cold inside my apartment (around 62 degrees, but it feels colder cuz of the drafts). Apparently neither my girlfriend nor the other tenants think this is a big deal, which has killed my momentum in trying to get the landlord to do anything. On the plus side, I'm surprised at how good the elecriticity in this old building is; I'm running space heaters and have yet to blow a fuse. My place in San Francisco would blow a fuse if the refrigerator happened to start a cooling cycle while I was vacuuming.

Maybe someone can help me find a new digital camera. What I want is :

  • Small point & shoot ; I really can't be bothered to carry around a DSLR , though I want most of the features of one.

  • RAW files. No jpeg. No in-camera noise correction. I want the original.

  • 10 or 12 bit intensity. So I can do software post exposure.

  • Manual controls for focus, exposure, etc. As close to plain old analog cameras as possible.

  • Very fast response time from button pressed to picture recorded; I hate the cameras that take forever (yes I know a lot of that is the autofocus and face recognition and so on).

  • Things I'd like : optical viewfinder (I hate looking at the LCD), very simple single-button switch controls, not a menu system you have to navigate through, long battery life (no LCD is huge for extending battery).

The Panasonic FX 150 looks okay, but it's 15 MP which is worrisome. The LX3 looks semi-ideal.

Also apparently there's this CHDK thing (see also ) which lets you hack any Canon Point and Shoot. Apparently the Canon P&S and the DSLR actually have the same chip, but for the consumer level stuff Canon just disables those features (like 10-bit RAW). Apparently the best for this was the Canon S70 which is not made any more.

I've read at many of the fancy photo places that you should get a physically large CCD (2.3" not 1.8" or 1.4") and that lower megapixels = less noise = better quality photos. That's sort of interesting to me theoretically.

Obviously larger CCD = better because more photons are coming in. Subdividing the CCD into more pixels gives you more resolution, but fewer real photons per pixel. I'm not sure what the right model for noise is, but I think it's pretty close to just constant intensity random noise that's independent from pixel size. That is, the signal measured in each pixel is :

Signal per pixel = # Photons in pixel + Random Noise of intensity N
S = P + N

Your signal-to-noise-ratio per pixel obviously gets better and better when you have fewer pixels, all the way down to the case of just one giant pixel which would be very accurate. However, obviously that needlessly decreases your spatial resolution. On the other hand, if you divide the CCD into too many megapixels you have too little signal per pixel and it becomes hard to tell real signal from the noise.

If we try to maximize the amount of real total information captured, there must be some sweet spot. The total information is like (# pixels) * (information per pixel). Information per pixel is maximum when # of pixels = 1, and it goes down to near zero when N >= P. So as # of pixels increases this must be some curve that goes up then comes back down and has a maximum at some # intermediate of pixels.

Anyhoo, supposedly the 10+ MP cameras make ugly noise. I think a lot of that perception is due to crappy denoising software.

I've read that the "RAW" coming out cameras isn't really raw; they still run denoise and stuff on it. What you really want is a floating point file that just gives you the voltage at each pixel. I'm sure the camera companies don't want to do that because places like "dpreview" would put up sample screens of what the raws coming out without processing would look like and they would look awful. Then some jackass would build in some denoising and their raw would look much better and retarded consumers would buy it because of that.

1 comment:

cbloom said...

The Canon G10 looks pretty good except for the fact that it's 15 MP and has a small sensor.

In the other ways it works (prosumer form factor, manual controls, real RAW, viewfinder).

Oh well, I guess it would give me lots of material for denoising experiments.

old rants