Actual Hyperfocal Distance, not the theory at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old February 7th, 2008, 10:12 PM   #1
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Actual Hyperfocal Distance, not the theory

Hi Guys,

As a complete newbie to the A1 and the forum, I have spent several enjoyable hours reading through the various threads and posts and discovering that the more I know the less I know. Which is great because it is seriously motivating me.

I have had what I hope is a thorough look for threads and posts on "Hyperfocal Distance" and found out a fair bit on the theory of the subject, but have not found any definitive information relating specifically to the A1.

My question (finally) is:

Is anyone able to tell me what the actual hyperfocal distance is for the A1 when fully zoomed out (wide), and/or any other zoom settings such as half in and fully in?

Thanks for helping.

Colin
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Old February 8th, 2008, 09:53 AM   #2
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Actual hyperfocal length for you will depends on how much "blur" (cc) you are willing to accept. The theoretical values are based on years of experience in photography and tests to determine what cc most viewers are willing to accept.

One could argue that the circle of confusion (cc) of the the 1/3" CCD is on the order of 0.004mm. This is value is reasonably consistent with the CC values for HDTV in 35mm format 9f (0.026mm) and super 16 format (0.013mm) and for 35mm film (0.030mm), and the 7x field of view factor compared to 35mm still camera lenses. (Note that digital still camera CC range widely from 0.004 to 0.024 mm.)

If you accept this, and assume an aperture of f/5.6,
At full wide the hyperfocal length is about 0.9m (3 feet)
At full zoom it is about 360m (1200 feet)

But you could try call Canon and see what they say.
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Old February 9th, 2008, 11:03 AM   #3
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Thanks Don,

I shall try out the distances you suggest and have also contacted Canon so will post their reply.

Regards

Colin
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Old February 13th, 2008, 03:40 AM   #4
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Colin - according to my amateurish calculations I've assumed a reasonable CoC to be .000075 in. which is pretty close to Don's suggested value of .004mm (=.00016 in.). My reasoning can be found here: http://www.dvinfo.net/conf/showthrea...rcle+confusion
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Old February 13th, 2008, 05:04 PM   #5
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To keep you informed.

On 9th Feb I submitted a question on Canon's website asking for information about the Hyperfocal Distance (such as charts, exact calculations based on the specific lens, etc.), and received reply today that my question "has been sent to the appropriate group and is currently under investigation."

Will post follow up as information becomes available, and am keeping all fingers crossed that I might get a usable answer.

Regards

Colin
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Old February 14th, 2008, 11:31 AM   #6
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One nice thing about video, in contrast to film, is that with a good monitor you can get immediate (~realtime) feedback on focus and depth of field, and adjust accordingly (as you can for exposure).

This is not possible with film where you have to 'soup' it first, and thus do not know for sure whether or not you need to reshoot the scene until ~the next day. Thus there is not much discussion of the topic among video folks. This is also the reason video folks do not talk much about equivalent ISO/ASA speed.
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Old February 14th, 2008, 03:18 PM   #7
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That is a thought I have been having a lot in the last few days. I guess I shall start another thread asking for monitor recommendations, as I was out trying to use the camera in fairly bright sunlight and I might as well have been trying to film with my eyes shut.
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Old February 15th, 2008, 07:24 AM   #8
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Don't forget to use the search capability. Lots of past threads on monitors.
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Old February 15th, 2008, 07:25 PM   #9
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The reply, not very helpful, from Canon is:

"Dear Customer,

Thank you for your recent enquiry regarding your Canon XH A1.

Please be advised that Canon do not publish information regarding the hyperfocal distance of their lenses. We also have not developed any formulas for calculating this value.

Third parties have investigated this previously. A commonly used formula is:

H = (fNc)+f

H is hyperfocal distance
f is focal length
N is f-number (f / D for aperture diameter D)
c is the circle of confusion limit

However, please be aware that we have not investigated this formula ourselves and can't guarantee the accuracy of the results that it provides. You use it at your own risk."

I guess I could submit a question asking the circle of confusion limit is!!

Colin
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Old February 16th, 2008, 03:16 PM   #10
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The issue of course, is that hyperfocal length, and circle of confusion (in some of its use forms) for that matter, in the context being use in photography is a question of what is acceptable to the viewer. How much blur can you accept? Some still camera lenses have a depth of field scale of sorts, related to hyperfocal length, but the concept has a more clearly accepted common meaning in photography; i.e., an average person viewing a 8"x10" print at 25cm distance.

For video it will involve questions such as the resolution of the viewing system, the viewing distance, etc. and ther is no common standard. Canon no doubt does not publish figures for video lenses because there is no clear standard for this.

Visit http://en.wikipedia.org/wiki/Circle_of_confusion for some more information on CoC.

Sometimes I think we are trying to make thing more complicated than they already are.
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Old February 18th, 2008, 03:47 PM   #11
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Thanks Guys

Thanks for all the advice guys.

The way to go is obviously practice and a monitor.

Appreciate the help.

Colin
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