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Old June 13th, 2005, 07:57 AM   #1
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How to get the best resolution in a 3" x 8" field of view

Hi,

I'm new to video recording and while searching for a camcorder for a specific application I've been bogged down by the familiar tradeoff between field of view and resolution.

I'm looking for a camcorder with which I can record in a resolution that (during playback in slow motion) allows me to read ~ 1 mm colored number tags stuck on bees that are moving around in a ~ 6" x 8" area. I will record under moderate light using a tripod and I can get very close to the object. Is this doable with a budget of about $5000? I can increase the lighting and decrease the field of view in that order if required to though I won't be happy doing them.

I've been trying to get demos with different cameras on my bee setup but it seems to me that camcorder dealers are not very enthusiastic about doing extensive demos with systems at that price range. Two dealers have at least advised me in some detail and one of them is pushing me toward the Sony HDV system while the other thinks the Canon XL2 with additional lenses will be my best bet.

How well do these two systems fit my application? Are there other systems better suited for this job? Please let me know if I need to supply further details about my setup for an answer to my question.

I look forward to your valued opinion and thanks in advance.

dhruba
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Old June 13th, 2005, 03:36 PM   #2
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Dhruba,

I had an earlier model compact JVC camcorder, as well as a newer HD-10, and both have a mode called "tele macro". When enabled, it allows close-ups while in the telephoto zoom position. It's about the same field of view as the wide macro, but you're much farther away, not casting a shadow on your subject. I imagine this is pretty much a standard feature of JVC. I haven't seen it anywhere else.
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Old June 14th, 2005, 06:24 AM   #3
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Thanks for the reply Dave. I'll try to look into the JVC camcorder if I can lay my hands on it. Excuse my ignorance but I've one question. You mention that I should explore the tele-macro mode but given that I can get as close to the subject, why do I need the "tele-" aspect of the lens? I somehow thought that I would rather need sort of a wide-macro lens to cover my 6" x 8" area in macro mode. Could you please explain?

Thanks.
dhruba
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Old June 14th, 2005, 01:23 PM   #4
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Dhruba,

Most macros work only in wide angle. This means that for the tightest view your lens may be less than an inch from the subject, and your camers casts shadows on the subject. With tele macro, you can be a foot or farther away and still have a close view. Portra lens adapters allow close focusing with lots of options, but you must have a filter mount on your lens.
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Old June 14th, 2005, 02:28 PM   #5
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Do you mean that you want to constantly record the entire 8" x 6" area? If so, at standard DV resolution, those 1mm tags are going to be about three pixels across. HDV within your budget won't give much better recording resolution.

Are you simply interested in logging the data, or are the aesthetic qualities of the picture important as well?

How often do you need to sample the positions of the bees?
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Old June 14th, 2005, 04:54 PM   #6
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A still camera connected to a computer with some sort of capture software might also work??? There are various stop motion and time lapse programs that should be able to take a shot over a period of time.

Frame rates would be much lower though.
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Old June 20th, 2005, 02:37 PM   #7
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Thanks for the all the replies and terribly sorry for the delay in responding but I never got any mail from the forum saying I've replies waiting. Then I was moving (I've to do it again next week) and after getting back to office when I decided to check the website anyway I couldn't find the thread. Grrr.

First replying to Dave, I get the idea about the telemacro. Thanks for clarifying that.

Now to Steve. Yes, I would like to do say three 1-2 hour continuous samplings on the 6" x 8" area. I'm not too interested in the aesthetic quality, I need the data: which bee interacted with who for how long and in what order. I can reduce the the 6" x 8" sampling area or sample each area periodically though it would be less than what I wanted. So, do you think 3 pixels is too low to read a 1 mm tag and HDV in my price range is not a solution? How high one has to go in price to get exactly what I want, if at all? Also, are there any automatic devices/tripods/mounts which let you move your video camera so that it can periodically scan a given area at some given interval?

Next to Glenn. Can you please explain your method a bit more? Each interaction lasts for about 5-10 seconds and I thought with time lapse I'll miss out a lot. I can probably borrow and test a Canon Digital 8.2 megapixel EOS 20D that can shoot at the maximum of 5 frames per sec. While the motion no doubt will be jerky I can probably still get the interactions. However, with continuous shooting for say 1 hr I guess you've to store/record directly on to a computer hard drive. How do you do that? How much space do you need to record at that frame rate for 1 hr? How much space would 1 hr of Hdv take up?

Thanks once again for the replies and I look forward to continuing this conversation and decide on something.
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Old June 20th, 2005, 06:24 PM   #8
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1- Idea: Borrow that Canon still camera for testing. You should be able to figure out which method will work for you.

Take a test shot, and scale it down to HDV size. If you can read the tag at that resolution, then HDV should work for you. *A HDV camera will shoot with slightly less resolution (depends on sampling and resizing algorithm) and with compression artifacts. I am guessing these two things would have neglible impact for you.

At the same time, you could also try setting up the still camera to record to a computer and see if that works. You can check if you can manage to set it up, and whether or not the frame rate would work for you.


The Canon should have macro focus so that should work for you.
If you do not have enough depth of field, you will want to make the iris/aperture smaller. This will make the image darker, so you may need to add lighting. Probably use flourescent lights and move them close... they put out low heat and are cheaper than the alternatives if you are paying for your electricity. If you have sunlight, then don't bother with lighting because the sun is very bright.
Focal length/zoom: If you can't move the camera closer, then look into getting a lens with a long focal length.

2- Setting up a still camera to record:
I'm not exactly sure about the details for this.
You need:
A program that can capture time lapse. I'm not sure as to how many frames a second such a program can capture. There may be some factors that limit how many frames/second the whole system can capture (i.e. speed of the USB interface, whether the camera can transfer a compressed JPG over USB or if it has to transfer a RAW file).
You probably want to transfer JPGs.
As far as hard drive space goes, you should be fine. In the worst case scenario, the camera would put out 100MB of data per second [which is too much for USB]. 4 250GB drives in a RAID 0 set would cost <$1000 and would store ~2.5hours.

I don't own a digital still camera so unfortunately I can't give you very much information on this.
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Old June 20th, 2005, 07:56 PM   #9
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Glen,

Thanks for the prompt response. I've two more questions about your idea.

1. Can the still camera motors handle 5 frames per second shooting for 1 hr or so on a regular basis? I'm just trying to be a bit cautious since it would be a borrowed camera.

2. What do you mean and what do you want me to do when you say scale down a shot taken with the still camera to HDV size. I do have a few shots on my computer that I've taken with this camera at some point and I can work on them.

Thanks again.
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Old June 20th, 2005, 07:58 PM   #10
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1- I never thought about that. Does that camera have moving parts? (i.e. the shutter might be a moving part)

2- Resize the image in an image editing program. i.e. Paint in MS windows (hit crtl e)
I don't think Paint reads the RAW format.
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Old June 20th, 2005, 08:04 PM   #11
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Glen,

Ctrl E in paint tells me that the resolution for this .jpg file is 96 x 96 dots per inch and the w x h is 3504 x 2336 pixels. So what do I resize this to for the HDV comparison?

Thanks.
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Old June 20th, 2005, 08:59 PM   #12
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Quote:
1080i format consists of 1440 x1080 pixels, sampled 8 bit 4:2:0 and then compressed 60 to1 to tape. Data rate of 25mbs

720p format consists of 1280 x 720p sampled 8 bit 4:2:0 Data rate of 19mbs
I would try resizing to:
1440 X 1080
and...
1280 X 720
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