crop factor

Some photo stuff: Crop factor.

Crop factor seems to come up a lot. Let's start from the beginning.

Crop factor is caused by the fact that the sensor in many cameras is smaller than 35mm film was.

If the sensor is APS-C (NEX-3, NEX-5, Nikon D7000, Canon 5xxD, 7D, x0D, all Pentax dSLRs) then the crop is generally around 1.5x, as the sensor is 2/3 the size of full frame.

With me so far? good.

The issue is that the viewpoint and field of view of the LENS does not change, but because of the smaller sensor size and the therefore restricted view shown to the sensor, it appears as if the lens "got longer". It didn't, it just looks that way. As part of the package, you get effects on depth of field, too (smaller sensor = more of the pic in focus).

Positive: long lenses "get longer". So you'll see a smaller cutout but it will still be detailed. This is good.
Negative: short lenses also get longer. So really wide angle is no longer possible, as you're always working longer than on full frame.

What this is useful for is one thing, and one thing only in my book: comparing what lenses from different systems will do in terms of one another.

Pancake 16mm on APS-C is FF-equivalent of 27mm or so. Pentax' 24mm --> ca. 36mm.
On Micro-4/3 (so a GH-1), it's Pancake 20mm --> 40mm as the sensor is smaller. This is *really* nice to know as otherwise you might be buying what you take as being a "wide" lens and it's really not that wide at all. Back in film days, 28mm was considered "normal" - so that's around an 18mm in crop terms - and anything lower than that was wide. It's not changed that much.

I quite like the Pentax Q way of dealing with this issue, removing the mm numbers from their lenses. I presume the idea is to reduce confusion, but whether it will work or not is another story....

If you want to take, say, car pictures from up close and don't mind distortion, you'll need something shorter than 18mm. 10mm will distort, anything much lower than 14 will visibly distort. If you can live with this, go for it.

If you need examples, go check out pbase and search on the lens. You'll see exactly what it's capable of. I'd strongly recommend this for any prospective purchase.

Another decent article on this (including pics): http://en.wikipedia.org/wiki/Crop_factor

late addition: http://www.kenrockwell.com/tech/crop-factor.htm


- Bret

CPU coolers

next problem... .

The cooler that's in place right now is a passive one, fed by a snail-formed fan which is noisy as hell. So, I removed that and put the 'board in a case... and promptly got a "wii ooo wiii ooo wiii ooo" alarm. Overtemp.

Dumping the fan from a 775 socket factory 'sink sorted that out, but I need a more permanent solution.

So I'm going to get a 92mm fan and wire it in place. I can't be bothered with *another* €50 (there are two machines...) and then no space, so it's going to go like this.

Air sucked in from on top of the CPU, pushed out of the case by the PSU fan. More "warm" air pulled in by a 120mm in front of the old 5.25 optical drive place - which will be converted to 4x3.5" just as soon as I have a decent method to do this, i.e. longer screws or a commercial solution - and pushed out via an exhaust fan at the rear of the case.
I'm dallying at the moment on the idea of an nxzt case, as that would solve the location problems and would probably look good, but I'm also limited to "only" 8 disks there, too. I need to think that one through.

- Bret

RAID card

I actually fitted the RAID card last night and right now, the machine spins up with 5 1TB and 1 1.5TB drives in place. The other 1.5 I'm saving for my desk at work (I have 2TB on there at the moment and fully intend to replicate important changes to that disk on a regular basis). I has to have an e-SATA port multiplier, but I don't see that as an issue.

Next question is where all of this is going in the flat. I'm wondering what happens if I move disks around within the zpool... as in they get a new name as they're on a different port. Of course, I could just mark which disk is on which port.

0.7 works....

freenas 0.7 works. in 32-bit mode (which is fine as the machine only has 2GB of RAM anyway for the time being).

Cool. Tomorrow? RAID card.

freeNAS

more digging implies something which is actually pretty heavy to deal with. The *minimum* system requirements for FreeNAS8 are now 4GB memory.

What?

When did FreeNAS morph from a system you could run on pretty much any hardware into one which required a serious machine? I know, hardware is supposed to be cheap, but still, this has made me really wonder.

I've downloaded an older version and will try that... and if it doesn't work, I guess I'm going ubuntu and software RAID as this is just silly.

running the p4sci - and FreeNAS won't

I'm kind of annoyed. Both the P4SCI boards work, and the one I've transplanted into the old midi-tower case I have lying around boots sort-of correctly. Only thing is that it simply won't start FreeNAS.
My previous experience of FreeNAS is only good. It simply ran on old hardware and that was it. Now? I don't know. I've tried pretty much everything I can (HT off, limit MaxVal etc) and it simply won't cleanly boot.
The only question now, then, is what to use instead. It was the ideal solution and I'm incredibly annoyed that it won't work. That the RAID controller doesn't see the disks doesn't really surprise me (I think there's a different issue there, mainly to do with the fact that I'm running a very high power P4 - TDP 87W - off of a minimally-sized PSU, along with 6x1TB drives) but the freenas thing sucks.

I think I'm going to strip to minimum hardware and see if that helps and then call it a night if it doesn't.

- Bret

other contributors

As of now, I expect the occasional post in the blog to come from a couple of other contributors, both of whom are part-time photographers. So you might not see just my content here ;)

I'll let them introduce themselves in their own time.

- Bret