# High Speed Photos Show String Whip During Power Stroke



## SonnyThomas (Sep 10, 2006)

The first and last are awesome pics of string whip...

Realize though, virtually all bows have approx 4" more string below the nocked arrow. Okay, the arrow is not centered between the axles.


----------



## SteveAllOut (Jan 27, 2009)

I cant offer an answer but i will say those are amazing picts


----------



## ron w (Jan 5, 2013)

yup, awesome shots, these and the high speeds of arrows in paradox as the leave the bow are just amazing to see what is actually going on.


----------



## Praeger (Jan 7, 2011)

SonnyThomas said:


> The first and last are awesome pics of string whip...
> 
> Realize though, virtually all bows have approx 4" more string below the nocked arrow. Okay, the arrow is not centered between the axles.


I understand that, but how would that explain the forward motion of the string below the nock?


----------



## Huntinsker (Feb 9, 2012)

That's cool and a dang good question. Makes you wonder why speed nocks are put on both top and bottom instead of just bottom. The peep on top may have something to do with it? This video doesn't show that at all http://www.youtube.com/watch?v=axJZSNIQxps


----------



## SonnyThomas (Sep 10, 2006)

Praeger said:


> I understand that, but how would that explain the forward motion of the string below the nock?


Don't know, but in order to see what is really going on we'd need frame by frame photos. However, I'm not going to lose sleep over it


----------



## Bushwacked (Apr 6, 2012)

The last pic is just amazing that the lower half of the string is that far ahead of the top.


----------



## dwagoner (Sep 27, 2007)

ive seen another of a single cam bow and it scares the crap outta me when i see it, its rather wild to look at some of them....lol


----------



## adamstephens (Mar 5, 2012)

Be very careful in analysing these photos this way. Some cameras, for example phone cameras without a proper shutter, will read the imaging chip in lines from one edge to another. This would mean that one edge of the photo will have been taken at a slightly different time from the opposite edge. This will cause the sorts of distortion illustrated.

On the other hand, they may have been taken with a camera with a mechanical shutter and be real effects.

Just be cautious.

Adam


----------



## chevman (Nov 3, 2006)

The top string being shorter than the bottom, hits resistance sooner(the end of the arrow) momentarily slowing it down until the bottom half of the string catches up to that same amount of resistance from the arrow. By the time the bottom feels resistance it is well past the plane of the top of the string.jmo.


----------



## duc (Jul 18, 2009)

All of these pics seem to be taken with an electronic camera.
Scan rate and shutter speed will ALWAYS so this sort of distortion.
It is not real. It is product of the camera.


----------



## Praeger (Jan 7, 2011)

chevman said:


> The top string being shorter than the bottom, hits resistance sooner(the end of the arrow) momentarily slowing it down until the bottom half of the string catches up to that same amount of resistance from the arrow. By the time the bottom feels resistance it is well past the plane of the top of the string.jmo.


I wondered the same thing, as it seems the only possible difference between the top and bottom side of the nocking point. As I see it, what keeps this from explaining what is shown in the photos is at full draw there is equal tension from each cam. At release the energy stored in the limbs causes the cams to rotate. The cams pull the string in at slightly different rates to compensate for the difference in string lengths above and below the nocking point so that that there is no vertical nock travel (setting aside some bows have a small amount of nock travel engineered into the cam spool rate). I don't think there is any moment where the bottom side of string has a moment of no/low tension compared to the top side. If there was a difference in tension between top and bottom limbs/cams, you'd notice it when you let down from a shot.


----------



## Praeger (Jan 7, 2011)

duc said:


> All of these pics seem to be taken with an electronic camera.
> Scan rate and shutter speed will ALWAYS so this sort of distortion.
> It is not real. It is product of the camera.


I think you are confusing the process an electronic image (analog or digital) is displayed rather than how an image is captured. While there is difference between the two type of digital image sensors; CCD and CMOS. Neither involves a scan rate. Scan rate is the process video images are displayed on a screen device. As to shutter speed, I believe that would only relate to blur in an image.

Virtually all high speed photography is digitally collected, stored and displayed. I would think if some aspect of it rendered it unreliable, it would not be used. Digital high speed photography is used extensively in scientific research and manufacturing.


----------



## bbjavelina (Jan 30, 2005)

I don't think the issue is digital, but the type shutter used.

Many point and shoot type digitals use what is (I beieve) called a rolling shutter. It an electronic shutter rather than a curtain type mechanical shutter and is well know for distorting moving objects. It's not typically noticed much with still images, but is very prevalent in videos. Airplane propellers are very noticeably distorted with this type shutter, as well as ohter objects moving fairly rapidly.

Any chance of knowing what cameras were used?


----------



## Praeger (Jan 7, 2011)

bbjavelina said:


> I don't think the issue is digital, but the type shutter used.
> 
> Many point and shoot type digitals use what is (I beieve) called a rolling shutter. It an electronic shutter rather than a curtain type mechanical shutter and is well know for distorting moving objects. It's not typically noticed much with still images, but is very prevalent in videos. Airplane propellers are very noticeably distorted with this type shutter, as well as ohter objects moving fairly rapidly.
> 
> Any chance of knowing what cameras were used?


I don't know what type of camera was used, the photos were posted on the TSAA Facebook page. Based on the other photos, they were probably taken in a burst mode, but no way of knowing if a point and shoot, DSLR, or HD video was used. 

As to distortion, CMOS correction is a post production technique used to correct the effect. Images in motion can appeared slanted, caused by passing through the capture window and recorded incrementally which results in a diagonal slope. Why I don't think this this accounts for the odd string whip pictured in the photos is that typically the distortion associated with CMOS image sensors is slanted in one direction. What makes the string whip curious is that the string is whipping in opposite directions. That would seem to be inconsistent with skewed slope appearance of CMOS recording line by line. That the whip can be seen in different photos, from different angles leads me to believe it isn't an illusion of the photo, but actually occurring. Probably answered only by 10K/sec frame slow motion video.

Here's a link to a plug in used in video post-production editing which shows some examples of CMOS correction.
http://www.thefoundry.co.uk/products/rollingshutter/


----------



## bbjavelina (Jan 30, 2005)

Prager,

Thanks for that link. As best I remember these artifacts are referred to as "skew". Is that right?

I do believe that high speed video is far more reliable than stills taken with a P&S or anything less than a DSLR.

I really want to know more about this whole thing. I just can't put any credence in the stills posted.


----------



## fotal (Jul 25, 2011)

the curve/skew is caused by the way the sensor unloads the data. , common name for the problem is "rolling shutter" check google.. . to confirm this, shoot the same photos with the camera up-side down. the string should be bending the opposite way..super high speed cameras for crash tests don't have these problems..but the cost real $$$....another thing that is interesting is if you shoot with a HS camera you can see how close to the rest the string actually comes and also how far back it bounces after releasing the arrow....


----------



## bbjavelina (Jan 30, 2005)

After checking the properties of all the above photos it appears that they were taken by the same camera, and all at the same pixel rate. The pixel count is relatively low. Of course, they would probably have been resized for posting.

This *SUGGEST* (nothing more) that they were taken with a Point & Shoot or phone camera. Very few photographers with a DSLR would opt for these settings. 

The amount of blur of the objects in motion also indicates that the shutter speed was relatively slow even though there was good light. Again not a setting that a photographer with a high end camera would normally choose for action shots. A slow shutter speed could be expected to increase the skew if a rolling shutter was used.

It just dawned on me that I may have one more tool to use to get to the metadata! 

Couldn't get to the metadata, so all of the above is just speculation. If anyone knows the photographer, get the camera specifics, please.


----------



## wolbear (Oct 28, 2005)

SonnyThomas said:


> The first and last are awesome pics of string whip...
> 
> Realize though, virtually all bows have approx 4" more string below the nocked arrow. Okay, the arrow is not centered between the axles.



And this is the correct answer. With there being more string distance below the nocking point, the "whip" has to occur to keep the string moving equally. If the arrow were nocked at the exact center of the string (same amount above and below) you would see an identical "whip" occurring.


----------

