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#1 Sergey Block

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Posted 10 May 2015 - 07:31 AM

Hi!
I have to shoot on Sony F5 in 240 fps in 2K.
There are two options in 2K: center scan and scan full frame.
To avoid cropping I have to shoot in "full frame scan" mode, but it's need a 2K low pass filter but I don't have such filter.
Are there any filter on front lens (4x4, 4x5.65?) is used for this purpose?
Thanks a lot for your help!

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#2 Robin R Probyn

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Posted 10 May 2015 - 07:40 AM

No front filter for this.. your better off in centre scan.. thats 2K anyway.. centre crop from the 4K sensor..   to avoid any possible aliasing .. at that frame rate the f5/55 will only record in 2K..


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#3 Mark Kenfield

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Posted 10 May 2015 - 11:08 AM

Just test it. You may find that aliasing isn't an issue in full-frame 240fps, in which case you're fine to use it. If it is an issue, halve your focal length and shoot with the crop mode instead.


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#4 Robin R Probyn

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Posted 11 May 2015 - 04:19 AM

Watch out for any light flicker too..   catches a lot of people out..   you,ll have to shoot XAVC with cards fast enough to handle the data rate. 

 

You should be able to rent the filter ?  its easy to change yourself.. 


Edited by Robin R Probyn, 11 May 2015 - 04:21 AM.

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#5 Sergey Block

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Posted 14 May 2015 - 07:31 AM

Thanks!

Do you mean flicker shooting with HMIs? Will Flicker-Free mode on a ballast solve this problem?


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#6 Robin R Probyn

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Posted 15 May 2015 - 01:45 AM

Found this on the inter web.. see below.. also for 240 fps you will need to shoot in RAW with the RAW recorder that fits V mount onto the back of the F5.. max to internal SxS is 180 ..

 

HMI lighting that uses electronic ballasts will not flicker, but they can be prone to another artifact. This would be Arc Wander, as described in the previous passage, the hot spot of the electrical arc that travels in the plasmatic gas within the glass bubble moves back and forth between the two cathodes. The resulting effect appears as shimmer and colour shift.

If one big light is used directly pointed at the subject, this effect can be quite obvious. If many lights are mixed together or if the light is punched through diffusion then Arc Wander can often be limited to an unnoticeable level. Additionally, Arc Wander is much more apparent in a dark studio scenario, when used outside to compliment natural daylight these effects can often be negligible.

With the 300Hz and 1000Hz High Speed Ballasts it is possible to achieve high quality flicker free images at frame rates of 1000 fps and in many cases beyond even with a single HMI daylight source.

This new technology supplies the lamp with a greatly raised square wave current rather than the typical 75Hz. High frequency ballasts are available for all wattages from 125 W – 18,000 W. It is recommended to still test the lamps at the shooting speeds required prior to a job.


Edited by Robin R Probyn, 15 May 2015 - 01:45 AM.

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