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View Full Version : is guncam footage slow motion or normal motion?



raaaid
04-06-2005, 09:07 AM
im just quite curious about it

i mean general of course there can be exceptions

WOLFMondo
04-06-2005, 10:16 AM
Depends what speeds its being played at http://forums.ubi.com/images/smilies/16x16_smiley-tongue.gif

Fennec_P
04-06-2005, 11:09 AM
In general yes, most is played in slow motion, like 2/3 or 1/2 speed or something.

I notice if you play PF in 1/2 time compression, it looks more like guncam footage.

EnGaurde
04-06-2005, 04:25 PM
from what i know, planes have magnetos, not alternators. Mechanics, correct me if im wrong...

i thought all the planes systems ran on batteries, not from juice drawn from any onboard generator?

therefore, it stands to reason that, the little electrical motor driving the footage reel may be subject to the amount of juice flowing thru it.

think of batteries running down / starter motor on your car getting slower as the battery drains.

i reckon that the quality and life of the batteries would have been low, the amps required to click over 8 gun trigger solenoids on the p47 for example plus driving the radio system and whatever else was thrown in, meant the speed of the footage recorded would have been proportional to how healthy the electrical system would have been.......?

hobnail
04-06-2005, 04:30 PM
The fps of guncams was particuarly poor, 12-15fps at best. Considering the vibration and violent movement the camera captured this only exacerbated the quality. That's probably why you perceive 1/2 speed as looking more authentic. I don't doubt that they were played slightly slower at times to allow better analysis.

My best guncam footage is usually that which I record with only 12-15 fps but play at near-real speed. eg this online kill:

http://users.on.net/apoulos/Bf109G6-R2-v-P47D22.gif

Fliegeroffizier
04-06-2005, 06:34 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:...
think of batteries running down / starter motor on your car getting slower as the battery drains.i reckon that the quality and life of the batteries would have been low, ...the speed of the footage recorded would have been proportional to how healthy the electrical system would have been.......? <HR></BLOCKQUOTE>

If that were the case, the camera film/shutter would have been activated LESS frequently, and as a result when the processed/developed film was Played/viewed it would appear to be running FASTer than normal, not slower.

Zyzbot
04-06-2005, 07:31 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:
from what i know, planes have magnetos, not alternators. Mechanics, correct me if im wrong...

i thought all the planes systems ran on batteries, not from juice drawn from any onboard generator?

therefore, it stands to reason that, the little electrical motor driving the footage reel may be subject to the amount of juice flowing thru it.

think of batteries running down / starter motor on your car getting slower as the battery drains.

i reckon that the quality and life of the batteries would have been low, the amps required to click over 8 gun trigger solenoids on the p47 for example plus driving the radio system and whatever else was thrown in, meant the speed of the footage recorded would have been proportional to how healthy the electrical system would have been.......? <HR></BLOCKQUOTE>


I found this on th eP-51 electrical system:

Electrical system- The aircraft has a 24 Volt D.C. system with a 100-amp generator. Some aircraft have an alternator installed. Normal aircraft have no AC electrical devices installed. A standard battery is used to provide starting and back up power. The aircraft does not require a ground power cart for normal use."

EnGaurde
04-06-2005, 10:51 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> If that were the case, the camera film/shutter would have been activated LESS frequently <HR></BLOCKQUOTE>

aah yes of course it would, like animation, more frames in the same time frame = slower motion.

therefore, less frames means less exposures and more gap between each frame.

well, so much for that theory. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

JR_Greenhorn
04-06-2005, 11:29 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:
from what i know, planes have magnetos, not alternators. <HR></BLOCKQUOTE>Magnetos and alternators are not mutually exclusive. A magneto is used primarily for ignition, although the AC current they produce can be used for accessories.
Small, genereally off-road only powersports vehicles usually work this way, because they often have a minimum of electrical accessories to power (usually only lights).


Alternators are used to produce current to charge batteries. In such a system, the battery powers the accessories, possibly including the ignition. The alternator "fills up" the battery with charge as the accessories run it down. As long as the alternator can produce more power than is being used, the system works and the system voltage is fairly constant. The AC source voltage produced by the alternator must be regulated and rectified to be used in the DC system the vehicle uses.

I can think of one aero engine off the top of my head (there are certainly others) that uses a battery-powered ignition system instead of a magneto. The Liberty 12 of WWI operated this way.


An alternator needs current from a battery to engergize its windings as well as rotation in order for it to produce power. Conversely, a magneto uses a permament magnet, so only rotation is required to produce power.



So basically, the ignition can be powered by either the battery (as in automotive-type ignitions) or a magneto. Similarly, the electrical accessories in the vehicle can be powered by the magneto or by a battery. A vehicle can use either system for either task, so you can have a single shared system (automotive) or two dedicated systems (most aero).
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:
i thought all the planes systems ran on batteries, not from juice drawn from any onboard generator? <HR></BLOCKQUOTE>This sounds correct, unless there were any APU-equipped prop planes. Perhaps some bombers might have had them?
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:
therefore, it stands to reason that, the little electrical motor driving the footage reel may be subject to the amount of juice flowing thru it. <HR></BLOCKQUOTE>True, but as above, the variance in the source should be minimized since it is supplied by the alternator-charged batteries.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by EnGaurde:
think of batteries running down / starter motor on your car getting slower as the battery drains.

i reckon that the quality and life of the batteries would have been low, the amps required...meant the speed of the footage recorded would have been proportional to how healthy the electrical system would have been.......? <HR></BLOCKQUOTE>What you are describing here is known as a total-loss electrical system. Such systems aren't very common in vehicles. The starting system of a car (or any electrically started vehicle) operates as a total-loss system temporarily. The alternator (or other electrical power source) doesn't spin fast enough to produce significant charge. Thus, if the engine is difficult to start, the charge can be drained from the battery. Once the engine starts and the alternator spins faster, charging is provided.


I've driven a few vehicles with constant-loss electrical systems (and no magnetos). Once they begin to deplete the battery's stored charge, the ignition will not fire the engine under load, which gets worse until there is no spark at all.

mauld
04-07-2005, 06:22 AM
Gun camera footage was normally only taken when the guns are fired, Say for a spitfire A1 about 14 seconds max and probbly shorter for cannon armed aircraft. So it makes sense to slow the footage down so us humans can view it comfortably instead of it being a "blink and youll miss it" affair.

raaaid
04-07-2005, 10:50 AM
the variation of intensity doesnt necesary means the slow of the camera since clocks dont slow down because of a low intensity of the battery

i supose guncam footage was taken mainly to teach pilots shooting so the closer to reality the footage the better, slowing the speed would lead to great confussion

besides to me the footage ive seen seems not at slow motion but at normal motion and normal size (if you look at it at the right distance)

VW-IceFire
04-07-2005, 10:57 AM
I had something on this...I'll look it up.

Gun camera footage was used mostly to confirm or help confirm kills. Plus it would help the pilot in question to better aim his shots. Oh and for the occasional propoganda flick.

CAPT_COTTON
04-07-2005, 12:04 PM
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First of all Dont compare the equipment of WW2 to mondern cars and bikes not the same. http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif
most were 24 volt and they only had 6 volt batterys wired in series. the engs were started by hand cranks or starter motor or a gun fired thingy ???. http://forums.ubi.com/images/smilies/354.gif
the magnetoes were the first electronic ignition systems and they were not used to run other electronic systems [40000 volts plus].
they were a distributator that made there own electricy and for aircraft the more the merrier. http://forums.ubi.com/images/smilies/25.gif

In WW2 [1938-1945]there were only genarators used either nective ground or in europe they were postive ground and the mondren alternators did not come in to being till the 60s-it generates 110 volt alt current and then it is converted to 12 volt direct current and sent to batteries. http://forums.ubi.com/images/smilies/10.gif

Now to the gun cameras. In WW2 nearly all small hand held cameras were wound up and a spring ran the film thur the camera. the cameras were high speed cameras [slow motion]which means take pixs at fast FPS and then play at regular FPS and the action is slowed down so you can see what happen better.when first turned on by by the firing of guns they ran fast but as the gun ran out of ammo the camera spring would run the camera slower and you get different FPS in different views.This speed also was dependent on how much did ground crew wind up the camera????What if ground crew forgot to wind camera and there was no record of kill that is not an officer i want to be in front of. http://forums.ubi.com/images/smilies/784.gifhe he

Now why does the gun camera shake? well ever been around a 50 cal. or 30 cal. or a 20mm or 5 inch MG or gun when they are fired http://forums.ubi.com/images/smilies/53.gif, you can feel the viberation in the ground standing beside the plane and by the 5 inch gun in your toes and ever wonder why so many people coming back from WW2 had lost there theeth early in life.?The lines in the camera views are caused by the projector that is showing them the more they are played the more you get lines in them so when they were first shown in world war two there were no lines in them .Now 60 years later and looked at by lot of people you got lots of lines.
When i was in the ROTC in the 50s we watched gun camera films that were taken in WW2.Some were blurry [guns firing caused that]and some were too fast and had to run over again and again to see what was happing in them [wernt wound up all way]They were great for us preTV kids and we watched them every chance we got.
Some of the films had no lines in them but i bet when we got thur with them there were a lot .he he http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

I was an aircraft mechinic [Airdale]in US NAVY from 1959 to 1964 and worked on same engs used in the planes of WW2. pratt and whinty radical that was in our planes the R6D or DC6 also got to fly in them all over pacific. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

I will always think it should have worked.cotton8842@msn.com

EnGaurde
04-07-2005, 10:25 PM
well, no point in posting anything else, cottons fairly nailed it with that first hand account.

gold.

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