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-   -   Best way to grab frames? (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/67713-best-way-grab-frames.html)

Colin Jones May 19th, 2006 08:57 AM

Best way to grab frames?
 
I see a lot of you post screen grabs as samples.
What methods do you use to grab them? Is there a way that produces the best results? I tried exporting a still frame from Final Cut Express but it wouldn't open in anything but Quicktime even tough it was a JPEG. I am not looking for software specific answers but more general answers to questions like

Do you get better results from 24p rather than 60i?
Do you run a de-interlace filter before grabbing?
What format do you save the still in?

I am looking to get good frame grabs for Menu BGs etc. and the occasional sample to post on DVinfo.

Colin

Ian Scanlan May 23rd, 2006 08:27 AM

I obtain my screen grabs through the export frame feature in adobe ppro2. There will be an issue with interlacing (on a Tv screen, a still image will shake like mad - not good). I get around this by using the video filter in Photoshop. I also will add a guassian blur filter. A 24p screen grab will look better. The reason why your screen grab is opening with qt is because in your preferences, there is a setting which says that jpeg's wil open with qt.

Eric A Robinson May 23rd, 2006 08:37 AM

grabbing frames
 
Hi there

I normally export stills as png. files from FCP, for if need to edit the frame and add an alpha channel in photoshop to use in Motion it always works well. As I always shoot in 25P progressive interlacing is not an issue. ( or I never worry about it)

Greg Boston May 23rd, 2006 08:38 AM

Quote:

Originally Posted by Colin Jones
I tried exporting a still frame from Final Cut Express but it wouldn't open in anything but Quicktime even tough it was a JPEG.

Right click on the file, choose Get Info. At the bottom of the dialog that opens, you have a choice to open just that file with another application or...set it so that all files of that type open with a particular application (such as Preview).

As for screen grabs, if you know you will want them, shoot in 30P with a shutter of at least 1/250 if possible. This will give you a nice clean frame to grab out of FCE.

-gb-

Colin Jones May 23rd, 2006 09:47 AM

The problem is not that the association is wrong. The file format is not readable in anything but Quicktime. If I try opening in Photoshop it fails with an "Unknown File Format" error. The same in any other program I try opening it in. The only thing that will open it correctly is Quicktime Player.

My only choices from Final Cut Express are JPEG or PICT.

Colin

Ian Scanlan May 24th, 2006 11:06 AM

Quote:

Originally Posted by Eric A Robinson
Hi there

I normally export stills as png. files from FCP, for if need to edit the frame and add an alpha channel in photoshop to use in Motion it always works well. As I always shoot in 25P progressive interlacing is not an issue. ( or I never worry about it)


Hi Eric.....what sort of things are you filming with 25P? I tend to do a lot of filming with bands/theatres....with pans and zooms. I was just wondering if you ever use pans when you shoot in 25p.....my experience is that you have to pan really slowly. I may be doing something wrong!! Thanks

Doug Boze May 25th, 2006 02:31 PM

Displaying frame grabs properly, 16:9
 
Here's something I've been scratching my thatch about: I've been recording in 30p 16:9 on the XL-2. I want to capture frames (no problem in PPro) and save them as .jpgs (again, no problem) but what about aspect ratio?

PPro will export the frames as 720x480 (1.2:1 pixel ratio) which is correct, but of course I want to display the grabs in their correct aspect ratio. So it seems I have only two options in Photoshop: resize them to 854x480, or to 720x405. The former interpolates and creates new pixels, the latter discards them. I can't decide which is the better route.

Are these the only options?

Colin Jones May 25th, 2006 03:09 PM

Quote:

Originally Posted by Doug Boze
Here's something I've been scratching my thatch about: I've been recording in 30p 16:9 on the XL-2. I want to capture frames (no problem in PPro) and save them as .jpgs (again, no problem) but what about aspect ratio?

PPro will export the frames as 720x480 (1.2:1 pixel ratio) which is correct, but of course I want to display the grabs in their correct aspect ratio. So it seems I have only two options in Photoshop: resize them to 854x480, or to 720x405. The former interpolates and creates new pixels, the latter discards them. I can't decide which is the better route.

Are these the only options?

Doug,

I know there is a difference in pixel aspect ratios but am not sure what it is and why. I see you say that 1.2:1 is correct so I am assuming you know about this. Can you explain? Or for that matter anybody else out there in DV land.

Colin
PS. Personally I would go with discarding pixels as I think you will notice the quality change more on the wider version as there are more pixels affected. But I would guess it would be more of an end use size issue than anything else.

Doug Boze May 26th, 2006 01:57 PM

On a PC, like what you are staring at now, pixels are square or have a 1:1 width:height ratio. In DV, the standard 4:3 screen ratio is 720x480 pixels, which have a 0.9:1 width:height ratio. DV 16:9 widescreen or letterbox screen ratio is also 720x480 pixels, only they are 1.2:1 width:height ratio.

But since computers can't display anything other than square pixels, something has to be translated. If you show a frame grab of Dv 4:3 video, it will look okay, but actually will be pulled 10% wider than it really is. If you show a frame grab of Dv 16:9 video, it will be exactly the same size, but everything will be squeezed or compressed horizontally.

I don't think there is any non-lossy method of showing frame grabs on a PC.

Colin Jones May 26th, 2006 02:05 PM

Quote:

Originally Posted by Doug Boze
On a PC, like what you are staring at now, pixels are square or have a 1:1 width:height ratio. In DV, the standard 4:3 screen ratio is 720x480 pixels, which have a 0.9:1 width:height ratio. DV 16:9 widescreen or letterbox screen ratio is also 720x480 pixels, only they are 1.2:1 width:height ratio.

But since computers can't display anything other than square pixels, something has to be translated. If you show a frame grab of Dv 4:3 video, it will look okay, but actually will be pulled 10% wider than it really is. If you show a frame grab of Dv 16:9 video, it will be exactly the same size, but everything will be squeezed or compressed horizontally.

I don't think there is any non-lossy method of showing frame grabs on a PC.

Thanks Doug,

So to make 16:9 the correct size I would need to make the width 20% wider while keeping the height the same. Correct?

Colin


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