Just glancing through the latest Camera House catalogue, there are quite a few nice looking "high definition" camcorders around now. They mention being able to take still images anywhere between 2 megapixel and 10.2 megapixels, which is kind of confusing. Is it because they are not deriving the image from the Video feed, but only taking that shot in a different still mode?

To give context, here's the reason I'm asking. I'm an optometrist, and I see a lot of very elderly people. I need to see inside their eyes, but the instruments are hard to use with them because they tend to not be very steady with holding their gaze still, and it's a strain on the back to hold the instruments there for a long time while I try to assess if their eyes are healthy or not.

What I'd like to do is mount a camera on my equipment, so I can take a photo when I get it all aligned, and then just look at it on my laptop (in comfort!).

I've been working on using a still camera, but one of the challenges is taking the photo just at the right time, just as I get all the lenses etc aligned with their eyes - you often get only fleeting glimpses. It struck me that if the HD video is a good resolution, I could just record for 30s or so, download the video stream to my MBP C2D 15" (would FW800 be fast enough?) and then select the best still frames from the video feed to analyse - that way I can concentrate on aligning it all perfectly, instead of having to worry about clicking the shutter at the right time (which might make the camera shudder a little anyway). Then I'd discard the video, and be left with my beautiful still frames...

So, the make-or-break is what equivalent megapixel image I could get from the actual video.

Can anyone help?

Well, nobody eh?

Just in case anyone later searches for an answer to a similar query, here's what I've worked out.

1) A full HD frame should be about equivalent to 2MP. (1080 x 1920). Various HD camcorders offer stills that are higher than that, but they only take that as dedicated stills, rather than part of a video stream.

2) I couldn't find a single HD camcorder that has a firewire socket. They are ALL USB only, which really bites, since that's slower than even Firewire 400, let alone 800. Seems crazy, but I guess it's because Windoze machines just don't really go the FW. For my purposes, I need a fast download. Meh.

Supplementary question then is: how fast would (say) a minute of full HD video take to download via USB?

Canon HV 30 is FW400.

Still frames from the HDV is about correct as you stated, but don't forget to de-interlace the frame if you go down that route.

I don't think using a HDV camera for photos is the best option, I think a DSLR would be a better way to go, just learn the camera, get used to the DSLR and get more practice at it and before you know it you will be set up and shooting like crazy.

do you know what your talking about?
i have my doubts.

USB v FW will depend on what medium the HD footage is recorded on. Generally HDD and SS cameras will be transfered via USB. but tape such as HDV and DV will transfer via Firewire. USB just dosnt have the Bndwidth for SD or HD streams.

I exported some still frames from an HDV project i was working on, they were 1920 x 1080 so full HD res, and were comparable to my 10 Mega Pixel Cannon still camera

Thanks for the note about de-interlacing. Not something I had been aware of - is that hard to do? Would IMovie08 do that when it creates a jpeg? And would the de-interlacing mean I end up with a 1MP image instead of a 2MP?

DSLR isn't an option. I'm using it one handed, at best - one of the attractions of video is that I can set it going and then have both hands free to manipulate the optical equipment and hold the person's eyelids open, etc etc. Even if I have a hand free to click the shutter, the reaction time is an issue - for some patients it's really only a fraction of a second that everything gets aligned. Thanks for the suggestion though.

Well, I think you must be psychic there.

Okay, well if it doesn't even do SD, why do all the HD camcorders I looked at have USB?

Well that's good to hear. I figure if I can get a good 2MP image from HD video stills that will be quite good enough for my purposes.

Still hoping for some feedback as to how fast a minute of HD video takes to download over USB. If it helps, I'm probably looking at using a flash-based camcorder (Sony HDRTG1).

Not all HD camcorders will call it firewire. My Sony HCR5 full HD camera calls it iLink, some of the Canon cameras simply cal it DV/HDV.

You're right. Some cameras do *prefilter* the signal to remove high frequency detail to make it easier to compress, so they may not actually resolve very fine detail.

Also, you'd probably want to change the shutter speed. The default (which is 1/50) is probably not going to be fast enough on a still.

The funny thing is that the little bit of blur that comes with action is good for the perception of motion, but soft when viewed as individual frames.

Try this as a test if anyone's keen. Pan your camera across some text on a page. You should be able to find that text appears sharper when viewed as continuous motion, but if you pause and look at an individual frame, it's softer and harder to read !!!

Some kind of in-brain image processing happening there....

jb

get a Canon 5D Mk 2 and use the HD video

I was going to recommend that as well, but price might be a mitigating factor.

Thanks for the advice, but as I've said before I couldn't possibly hold a SLR - it's just too bulky to hold with one hand, especially as that hand would have the trigger, and it's way, way too heavy - 810g, and that's without any lenses. One attraction of the Sony camcorder is it's only 300g.

Hi -

As mentioned, the Canon HV30 has FireWire. Every HDV camcorder (tape-based HD) will have it, and the non-tape camcorders probably won't. Don't worry about missing FW800 -- with the compression applied, you only need ~3MB/second bandwidth.

For you, the very convenient feature of the HV30 is that it can shoot progressive scan (PF25 in the menus), so you won't need to deinterlace anything. Clean stills @ 25fps.

You should be able to simply plug it into your Mac in camera mode, launch iMovie and press record to get a live preview and a live capture. I stand ready to be corrected on this -- it works fine in Final Cut Pro. I've even been able to see (but not capture) live HD images through odd hacks built in Quartz Composer.

Summary, then: yes, live viewing and capture is possible, an HDV camera will work well, the HV20/30 shoots progressive scan that's ideal for your needs. Enjoy!

Thanks - that's a helpful tip!

It's still a bit on the heavy side, but I see Canon also do the HF10 and HF 100 flash-based camcorders, which come out at 430g, which *might* be do-able. They both do progressive scan 25P as well.

It would be perfect if the 300g Sony did progressive scan - on the specs it says "Video Data AVCHD 1080/50i. 1080/25P" - does that indicate progressive scan?