Long Throw Lens

J

Jeffrey Lebowski

New member
Can anyone tell me, when sticking a 22x or 33x Canon B4 Mount Lens onto an HPX-371 does the lens become more telephoto? because of the the chip size set?

We shoot constantly in a venue and we're always having to hire in a Canon 33x or 40x Zoom Lens for the rear Cameras (which are 2/3 inch size). They don't come cheap (around $450 US per day)

But we're looking at getting some HPX-371's to replace the 2/3 inch Cameras and were wondering if we can save money on cross hiring those big lenses and maybe just use a 22x zoom lens which would give is more magnification because of the the difference in sensor chip size.

Anyone like to share their experiences?
 
Hi found this link for you http://www.dvxuser.com/V6/showthread.php?t=180855 which talks about this.

Although Barry doesnt like the term crop ratio's its used regularily in dslr circles and i have the same thing when i mount 35mm L lenses to my canon 40d with its aps-c sensor.

Basically when you mount a 2/3 inch lens to a 1/3 inch chip camera, the light passing through the lens is meant to focus on a 2/3 inch chip. As the 371 chip is smaller it only "sees" the center part of the projected image hence the magnified image effect. ( Bit like using the crop tool in photoshop ).

The link above seems to imply that you may gain a 2x mag of lens on the 371 cam, ill search a bit more to confirm.

In case your interested heres a good explanation of crop factor from Dpreview where it shows the effect on SLR's but the same would apply here too :)

http://www.dpreview.com/learn/?/Glossary/Optical/Focal_Length_Multiplier_01.htm

p.s. ill need the more techy guys here to confirm but as the 300 series cams will only be using the center portion of the 2/3 lens you may be able to use cheaper 2/3 HD lenses ( maybe even broadcast ones?)

The more expensive lenses have better optics to ensure good edge to edge sharpness and to minimize ca, the 300 series cams wont use the edges of the lenses so maybe it will make it a little cheaper for you?
 
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Yes, it's half the chip size so double the magnification. So the shorter lenses will work for you in place of a 40x.
But, when using lenses computed for larger sensors you have to be careful as theoretically they won't have enough resolution. Certainly be very wary of using 2/3" SD lenses on 1/3" HD cameras.
Steve
 
Billrat said:
You might want to take a look at this;

http://www.mtfservices.com/home.htm...ypage=flypage.tpl&product_id=11&category_id=2
Click to expand...

That would work, and give him telephoto on the cheap, but for live event coverage a photo lens will be a nightmare. No zoom servo (or capability for focus servos without expensive cine gear), difficult to focus, and long photo zooms will be much slower than the B4 zooms he's looking at.

I'm with steve, use the adapter and you'll get away with a shorter lens, but be very careful of lens sharpness; test it before the event, and an SD lens is almost certainly out of the question (unless you're shooting SD, but still test it beforehand).
 
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The reason i wondered about broadcast lenses as there was a good lens test on the hpx500 forum. Some of the high end 2/3 inch broadcast lenses were actually better than cheaper HD ones.(and a lot cheaper)

Mind you the hpx500 isnt full raster so that may tip the balance a bit.
 
I didn't look at any of the links, but another thing you may need to think about is an F-stop loss when using a larger lens. I've never used a larger lens with an adapter, but I am assuming you might lose a couple of stops of light when you do... Anyone? Bueller?
 
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