question on motion jpegs and ... artifacts?

Hi, new here and learning to use my new A590IS. I don't know where to post this, so forgive me if this is the wrong forum.

I took a short video of lightning the other evening, and was looking at it frame by frame, when I came across some strange... not sure what to call them. My brother suggested they might be compression artifacts (??) Thought I'd ask around on a forum, see if anyone has an idea, or more importantly if there is something wrong with the camera.

Guess I could always claim they are something supernatural I don't want to post all the individual images, so here they are on a page

http://members.cox.net​/dkopplin1/lightningmo​vie.html

thanks if anyone can help.

Those are not JPEG compression artefacts. An image from one frame is bleeding into the next due to a problem with the camera.

The strange part is, particularly on the last two images, the frame that is between these two does not have the streak at all. The image would be bleeding back to a previous frame skipping the one immediately before it.

So, bottom line is that something is probably wrong with the camera, then ?

It appears that your camera is suffering from excessive persistance. This is characteristic of a cheap sensor (not necessarily a cheap camera).

With some cheap sensors, extreamly bright objects have been known to persist for over 1/4 second when the overall lighting is very low. Lightnig strikes at night are good examples of this "phenomenon."

thanks for the replies.

Excessive persistence could explain it if the "ghost" image was in following frames, but this is showing up in a previous frame, taken 2/20 of a second before the one with the lightning bolt.

I'm guessing here, is the data stored in a temporary buffer in the camera, before it's actually written to the memory card ? So, maybe something is going wrong when it's buffered ?

I know movies are really meant to be viewed at a normal playback speed, but I was hoping to maybe be able to capture single frames, also.

Capturing single frames out of movies should generally be avoided due to the inherant poor resolution of single movie frames.
I'd agree with your thought that it's probably how the camera deals with the image files, rather than the sensor, considering that the bright streak skipped a frame.

dixiedawn wrote in post #6041804
thanks for the replies.

Excessive persistence could explain it if the "ghost" image was in following frames, but this is showing up in a previous frame, taken 2/20 of a second before the one with the lightning bolt.

I'm guessing here, is the data stored in a temporary buffer in the camera, before it's actually written to the memory card ? So, maybe something is going wrong when it's buffered ?

I know movies are really meant to be viewed at a normal playback speed, but I was hoping to maybe be able to capture single frames, also.

Frame-skipping persistance is typical of interleaved sensors.

Frame X captures a hypercontrasting image. But, because of interleaving, this image is captured on every other row of pixels.

Frame X+1 captures an image, but only on those pixels not used by frame X. There is not persistance from frame X.

Frame X+2 captures an image on the same pixels used by frame X. There is persistance from the hypercontrasting image for frame X.

Interleaving the sensor allows the camera to process one image while it is capturing the next, and is very common in the video world.

There used to be a videocam that used an interleave of four. This allowed the processor and memory to be relatively slow, making for a cheap camera, but kept the pixel cout high for marketing puroses. Not very ethical, but common in the videocam world.

20droger wrote in post #6044118
Frame-skipping persistance is typical of interleaved sensors.

Frame X captures a hypercontrasting image. But, because of interleaving, this image is captured on every other row of pixels.

Frame X+1 captures an image, but only on those pixels not used by frame X. There is not persistance from frame X.

Frame X+2 captures an image on the same pixels used by frame X. There is persistance from the hypercontrasting image for frame X.

Interleaving the sensor allows the camera to process one image while it is capturing the next, and is very common in the video world.

There used to be a videocam that used an interleave of four. This allowed the processor and memory to be relatively slow, making for a cheap camera, but kept the pixel cout high for marketing puroses. Not very ethical, but common in the videocam world.

A "Four Field" camera? Do you remember which brand/model?

One of the off-brands, I can't remember which.

But you see that kind of stuff advertised on very-late-night TV and on those channels that have more "Paid Programming" in their schdules than regular shows. It's avertized right there along with the Blue-Blocker sunglasses, and other rip-off crap.

"All for only 4 payments of 29.99, plus shipping and handling."

Just in case it isn't clear, the images are shown in the correct chronological order, the last image on the page was the last image in the timeline.

I do appreciate the responses. I guess I will have to just exchange the camera if they will still let me, and if a new one does the same sort of thing then I will just have to accept that it's a weird little quirk of the camera.