It is, because CoC is based on observing a finished print. A smaller original (smaller sensor) needs to be blown up more to get to that same print size.

Glad I could help. It took me a while to get my head around this when I was first comparing digital camera systems.

About noise reduction: yes it is a pain unless you have a pro rig worth thousands. So avoid it wherever possible. Get quieter recordings in the first place and gate/edit out the worst disruptions.

There's a good reason dialogue is often dubbed in post. Then it can be perfectly recorded with no disruptions. Otherwise, be prepared to redo takes when an airplane passes, a large lorry trundles past, etc. Protect all mics against wind noise and only record on still days. And soon.

Being acutely attuned to the actual sound being recorded is critical. That is why the sound recordist is a dedicated member of the crew who does nothing but wear sealed headphones always listening critically for problems. If you cannot afford a separate sound person then you are not going to get good sound. Period.

That is sometimes a necessary compromise, but be aware it is one.

I don't know what to say to those who recommend the Zoom units except they are dead wrong. I can only explain this phenomenon as due to the fact that video people often know little about audio. That's been my experience anyway. It pains me that people are getting such bad advice.

Simply hold the Olympus unit and compare the build to the Zoom H2. There is no comparison. Of course it is still a relatively inexpensive consumer unit, but unless you want to pay ten times the cost you are not going to get better. The question is: How cheap do you want to get? I recommend saving money only if huge sacrifices in sound quality and reliability do not result. Otherwise it's like recommending a point and shoot to someone who really needs an SLR, simply because the p'n's is cheaper.

First, list your requirements, then get the cheapest unit that meets these requirements. But don't compromise on requirements or you will be continuously frustrated.

Look up the specs of these units as actually tested, not as promoted by their marketing departments. The most important of these is the quality of the microphone pre-amp. All are more or less the same in terms of distortion. (Well, not really, but the differences are not as great.) However, the Olympus/Sony units are way out in front in terms of low noise. This won't matter if you are recording live rock music. But it will matter if you ever want to record ambiance, room tone or even dialogue in less than perfect situations.

To be specific, the Samson Zoom H2 has an EIN of -99dBu(A) which is abysmally high. The Zoom H4 is much better at -114dBu. The Olympus LS-10/11/5 are at -122dBu. For comparison, something high-end like the Sound Devices 702 is -130dBu, but that is a huge and heavy shoulder unit -- unfair to compare with hand-held recorders.

The difference between the Olympus and even the best Zoom is hence 8dB, a significant amount. Of course, you also need to pair up a recorder with a decent microphone -- but at least a good recorder will eliminate one weak link from the audio chain.

Buying in Europe the Olympus LS-5 is only 8 Euros more expensive than the Zoom H2. That's a no brainer upgrade.

Depth of field is dependent on exactly four parameters: the focal length, subject distance, aperture (F number) and the circle of confusion diameter. The first three are objective measures but the last is subjective, which makes sense when you consider how much something is out of focus is an individual determination. Only objects exactly at the focus distance are in focus; everything else is out of focus to some extent or another.

The circle of confusion is the smallest point that can be clearly discerned by the average person under normal conditions. The Zeiss formula relates this directly to the diagonal of the sensor.

So yes, DOF is certainly dependent on sensor size, as common sense observations show. The smaller the sensor the greater the depth of field, all other parameters being equal.

Only now saw this thread. So, a few things from a trained audio engineer...

K6 + M66 is a good low-cost solution for a mono microphone that you want to run without phantom power, since it uses its own internal battery. Sound quality is "good" and you will pay a lot more to get "excellent". I own this combo myself.

You will want some sort of a boom for it I imagine, depending on what you will be vidding. The easiest way to improve your sound is to simply get your microphone closer to the sound source. That means getting it off the camera. (Oh wait, Don said that already.)

It's easy to sync video with audio from a second source. Simply clap your hands on camera. In your video editor, put the audio track in line with the video (which has its own audio as well). Zoom in and get the clap peak exactly aligned. Then mute or delete the audio track from the video, leaving only the separate audio. Voila!

The Zoom H2 and Edirol recorders are poor: cheap build quality, bad soldering, high noise floor. Buy something better, like the Sony M-10 or the Olympus LS-5. I have written extensively about them on my blog.

Sigma seem completely out of touch with reality. Even if it was one grand I'd prefer the K-5, strictly due to lens availability and superior ergonomics.

With all respect, you need to learn a bit about how sensors and the eye work and realise that artificial sharpening added after the fact is just that... a trick to increase local contrast and fool the eye into seeing edge detail. I prefer a camera that does no such thing without me telling it to.

True sharpness is down to:
a) holding the camera steady
b) holding the subject steady
c) having enough depth of field to cover the zone you want in focus
d) having a fast enough shutter speed
e) having a sharp enough lens

It has nothing to do with Canon versus Pentax. If you cannot get a sharp image with the K20D you cannot get a sharp image with any camera and it is not the tool you should be blaming.

The short answer is... nowhere! The long answer is... Vivitar 28mm As FA31mm Replacement?

Oh wait, you are already out shooting. Oh well, show us how it went!

Wide is good for cities. I would take the Sigma 10-20mm and 50/1.4. When I travel I take the D12-24, FA43 and FA77 and never want anything longer.