help, can't seem to get a sharp image

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Karl Beadle

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help, can't seem to get a sharp image

PostFri Apr 11, 2014 8:12 pm

Hello everyone
I wonder if someone can help me, I am using a bmpcc with a lumix 14mm lens and I can't seem to get a sharp image. I use the green edge focussing setting but to no avail. I have posted a test video, the first clip is just colour corrected, the second clip is the same as the first but with a sharp mask added and the third is the same scene taken with a Gopro 3 for comparison.
Am I missing something or is this just the style of these cameras. Thanks in advance
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Dustin Boswell

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 8:19 pm

I can't really tell because of the youtube compression unfortunately, highres stills would probably be a better indicator.

Are you shooting wide open or fully closed? most lenses tend to be less-sharp when the lens is fully closed or wide open, but usually just down a few stops is just right.
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Peter Östlund

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 8:22 pm

I have the same lens and it is very sharp.
Dirt?
Dit you try to test shoot on something still?

Peter
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joechiazza

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 9:51 pm

Want to see where this goes.


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Pavel Lavrov

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 10:22 pm

High Frequency vibration is also an option. Any test still shots from tripod mounted camera?
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joechiazza

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 10:22 pm

I think it looks pretty good. I always have a tough time getting good ultra wide landscapes. I think certain filters cut down on the haze and also a polorizer could get you some better color saturation


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David Dearing

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Re: help, can't seem to get a sharp image

PostFri Apr 11, 2014 11:30 pm

If the gopro looks shaper (and it does), something is wrong. Shoot at the same location on a tripod and compare. If it's blurry on the tripod, it's something with the lens. If it's sharp, your copter is vibrating. Or your gimbal. Is your gimbal vibrating at all? I just set up one for my Hex and the vibration was so fine, it was almost a hum, so I let it go- but it made the video blurry just a hair. Tuned it out and it was perfect again. Are you using the same gimbal as you used with the gopro? BM camera might be too heavy. That's pretty much all I can think of. lol
David Dearing
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Karl Beadle

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 6:03 am

Just done a quick test. I have taken a couple of stills from two clips. I have moved in closer to the subject with the gopro so that both cameras are seeing the same picture and the the Gopro is definitely sharper than the bmpcc so I don't think its my gimbal that is causing me problems. Anyone got any suggestions

gopro
https://drive.google.com/file/d/0B4O9ktReAK9mdnlsTGp1bXRrRms/edit?usp=sharing

bmpcc
https://drive.google.com/file/d/0B4O9ktReAK9mazlVTXRUZXIxdVU/edit?usp=sharing
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Tom

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 7:03 am

What aperture are you filming at?
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AdrianSierkowski

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 7:07 am

On your BM, are you shooting raw? And if so, how are you debayering it? I would recommend trying a raw shot and debayering it in resolve. The Pro Res on the pocket always looks a little soft to me as well.
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Karl Beadle

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 8:36 am

the picture was filmed at f10 and in video pro res
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Peter J. DeCrescenzo

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 4:43 pm

biggles wrote:the picture was filmed at f10 and in video pro res


Bingo (probably)!

It's very possible you were seeing, at least in part, the normal and expected result of diffraction caused by using an aperture setting too-small for the size sensor in your cam. This is not an issue specific to BMD cameras; it can happen with all cameras.

A "S16" size sensor as in the BMPCC pocket cam will record sharper-looking images if the aperture is set to f8 or probably less. Most lenses yield their sharpest results between approx. f4-f5.6, although this varies with different lenses. For example, some lenses are sharp all the way down to their wide-open aperture, but this is rare. Best to test your lenses with your cam to be sure.

Also, some filters, especially all-but-the-best variable ND type filters, will undesirably soften images, sometimes only at certain focal lengths. Again, carefully test your filter, lens, and camera to determine what combination yields best results.

Of course, opening the aperture to lower f-stop values when shooting a bright scene will often mean you'll need to adjust exposure in part by using an ND filter. As noted above, some ND filters are better quality than others, usually proportional to their cost. YMMV.

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Tom

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Re: help, can't seem to get a sharp image

PostSat Apr 12, 2014 7:16 pm

Yea there you go f10 is the cause of your softness.

The following is not completely true for every lens, but in general:

Below 5.6 = shallow dof but general softness
f5.6 = sharpest setting
f8 = deepest DOF before diffraction introduces overall softness.
above f8 = deeper dof but also an overall softer image.


This is of course highly simplistic but it works as a general guide.

You are better off stopping the lens to 5.6-f8 and focusing it hyperfocal distance.
Tom Majerski
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Karl Beadle

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Re: help, can't seem to get a sharp image

PostSun Apr 13, 2014 3:21 pm

Thanks fellas that makes sense, I see why a lot of the reviews of this camera said you will need an ND filter now. I will duly purchase one and see what the results are
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Tom

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Re: help, can't seem to get a sharp image

PostSun Apr 13, 2014 8:06 pm

biggles wrote:Thanks fellas that makes sense, I see why a lot of the reviews of this camera said you will need an ND filter now. I will duly purchase one and see what the results are



Glad to have helped! :-)

I hope an ND resolves your problem.
Tom Majerski
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