lost frames

[alcol620]

Hi folks

Second post from a newbie.

Took some video of Saturn last night using Sharpcap. Set the frame rate to 10 fps and recorded on my laptop for just over two and a half minutes. This to my reckoning should have produced over 1500 frames. The resultant files, one had had 838 frames in it and the other 861. Am I missing something?

Thanks for looking

[oldpink]

yes its dropped frames
if you look at the capture detail at the bottom right of the capture screen it tells you No Captured, No Dropped and time taken
I normally set a specific frame count of say 1000 - 20,000 depending on the FPS rate, if its low 15 - 30, I set for 1000 if its up in the 200's I set for 10 - 20,000

[alcol620]

Thanks oldpink.

I didn't notice any of the numbers, simply watched the time count down. Must take more notice next time. Any ideas why it would drop or not capture nearly half of the frames?

[oldpink]

not sure exactly but most likely due to the filesize and the speed your USB can handle
the Author of Sharpcap posts on this forum so he may have a better answer

[knobby]

Or possibly the exposure time for each frame is set too long

[Steve Ward]

Job to tell without the camera details , there are a few potential reasons.

[alcol620]

The camera (webcam) can be seen at http://www.ebay.co.uk/itm/Solar-System-CCD-Astronomy-Imaging-Photography-Set-/380827149668?ssPageName=ADME:L:OC:GB:3160

[knobby]

What was the exposure / shutter speed ?

If it was longer than 1/10 th second then 10 fps will drop frames ... 

[alcol620]

Knobby

by exposure/shutter speed, do you mean the setting on Sharpcap. Not sure what this was at the time, simple adjusted settings so that I got what I thought was the best picture on the laptop screen. Will check this next time.

Thanks

[daz]

SC records the camera settings in a text file for you. This will be in the same folder as the captured file.

[alcol620]

Hi Daz

Just had a look and the text file attached to the image file simply sets out the following

DTCS033 CCD USB2.0 Camera

Frame Divisor=1

Resolution=640x480

Colour Space/ Compression=RGB24

No mention of frames

The file name under the image file does state the duration of the video clip, in the case of the Saturn file 1 minute 25 seconds about half the time that the camera was running

Not sure this tells me any more?

Regards

[daz]

I thought it recorded the exposure settings and other stuff as well....

As knobby said, it will be to do with the exposure and shutter speed settings... 

[alcol620]

Thanks Daz I will take this on board when we next get a clear night. Thanks for all the help

[alcol620]

Hi folks

Did further checks this afternoon, in daylight. Nowhere on SharpCap do I get any indication that I am dropping frames. I ran the CCD camera at 3f/s up to 30f/s and it always produced a video clip of half the length of the setting (the camera did run for the requested time) eg set up to get 2 minutes of video, the camera ran for 2 minutes, but on inspection the video was only 1 minute long. SmharpCap did not indicate any dropped frames. As a cross check, I substituted an Xbox webcam that I have recently modified, and hey presto, the Xbox camera did what it said on the box. Using 3f/s and 30f/s the Xbox webcam produced video clips of the length requested ie 2 minute setting, camera ran for 2 minutes and the video clip was 2 minutes. Information on SharpCap showed that there was a handful of dropped frames.

A bit of a mystery. Any ideas folks.

CCD camera is DTCS033 CCD USB2.0 

[Bizibilder]

The spec of your camera, according to the link you gave says:  "Software automatically filters out video frames most affected by poor atmospheric "seeing" leaving only the sharpest, clearest frames to be stacked and aligned into one high quality image"  So I assume that is what it is doing - basically grading the frames and deleting any that it considers "below par".

The "Sky's the Limit" website shows then out of stock so it's difficult to get the full data sheet.  However the Celestron website also quotes the "frame selection".  

Your camera seems to be a clone as it does not have the Celestron badge on it, but I maybe wrong on this.

[knobby]

Did you buy it from skies the limit ?

I'd ask them about it ... Alan is generally very helpful .

When you plug it into PC what is it recognised as ?

[alcol620]

Hi knobby and bizibilder

Yes got it off skies the limit. Contacted Alan and I am awaiting a response. Have been discussing imaging with Alan over recent weeks and sharing captures. Very helpful chap as you say. Only recently noticed the reduction in length of the video clips. Very strange that it is always around half of the setting length. ie set to run 2 minutes of capture and get 1 minute of video clip. Does seem unlikely that dropped frames would always be around half the frames!

When plugging the camera into the PC it sees it as DTCS033 CCD

The mystery of the lost frames continues

[Bizibilder]

It may be set up to drop 50% of the frames.  Often when taking planetary videos I deliberately discard at least 95% of the frames I take via the software "frame limit" setting!

[alcol620]

Didn't notice anywhere to change a "frame limit" setting. But will look next time. So much to learn on this subject. Wish I had started when I was younger!

[oldpink]

not all camera's offer all the features in the software
it may be your camera isn't reporting all the data so the txt file is limited