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Edit/Correct Light Fall-off at Edges in AVI Files?

Discussion in 'Digital Photography & Imaging' started by Alex Ethridge, Apr 20, 2004.

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  1. Alex Ethridge

    Alex Ethridge Thread Starter

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    I have an AVI file that is bright in the center and suffers a graduated light fall-off the closer you get to the edges. Is there a way to correct this light fall-off in any editing software?

    I have NEVER edited an AVI file or digital moving picture of any kind so I know absolutely nothing about it so far. So, please be kind with the technojargan.
     
  2. Fredledingue

    Fredledingue

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    There are two good softwares to do that: VirtualDub and Aviutl.

    When you open the avi file, you will have to apply a filter that do specificaly what you said.
    Such a filter, if it exists, you will need to download separatly, maybe from some other sites.
    I can't tell you which of these two programs have this filter or even if this filter exists.

    When you save as avi, select a compression or "codecs". A codecs is the kind of compression you want to apply, for example: DivX.
    You need to have this codecs downloaded and installed separately too if it's not on your machine yet.

    Here is AviUtl
    http://fullart.topcities.com/aviutl.htm

    Please read helps and instructions before starting.
    Feel free to ask more question if necessary... :)
     
  3. MustBNuts

    MustBNuts

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    I just took a look at the software I use (Ulead Media Studio Pro) and it has a couple of filters that might work....

    I realize that this doesn't help you, but it made me think - the problem you will have is that filters apply an effect to the whole frame, and unless you can find a filter that is the equivalent of a "reverse spotlight", I'm not sure you will achieve any great results.

    Just my two cents (sorry...)

    MBN
     
  4. Alex Ethridge

    Alex Ethridge Thread Starter

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    Thanks for the replies. I'll look into these possibilities. Sorry about being so long replying. The e-mail notifications here don't seem to be consistent lately.

    In film photography, we call that kind of filter "Graduated Neutral Density Center Spot". The most common use is to correct light fall-off at the edges of ultra wide-angle lenses. Those filters range in price from $600 to $2850.

    Please note, there is no typographical error in that pricing.
     
  5. MustBNuts

    MustBNuts

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    A filter, in video editing, is (thankfully) completely different. If I'm not mistaken, the filter you are talking about is a piece of hardware that sits on the lens of the camera.

    A filter in video editing is like a little program applied to your footage in order to create effects from one frame to the next.

    Have you ever worked with Paint Shop Pro or Photo Shop? If you apply a filter or adjusted color/brightness-contrast on a photo? It makes adjustments to the colors on the photo...same with a filter in video editing....

    My software has a "spotlight" filter effect that adjusts the footage to give the appearance that a selected object/area in the footage is spotlighted. Essentially, all it's doing is increasing the brightness of that item, while decreasing the brightness of the area all around it. (and it repeats this for all the frames of the vid).

    It sounds like you need something that does the reverse of that: decrease brightness, etc., in the center, and increase it on the periphery.

    MBN
     
  6. Fredledingue

    Fredledingue

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    Yes, a "filter" in digital image or video editing is a piece of software (often free). A plug-in if you will.
     
  7. Alex Ethridge

    Alex Ethridge Thread Starter

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    This is all good information; but, I don't have any experience with this at this time. I haven't ever edited even one video in my life. I certainly cannot develop a plug-in like the one I need so if someone hasn't already made such a plug-in I'll probably never get this job done.

    Video editing to me is sort of like being lost in a cole mine without a lantern. I don't have any idea where to even start. I guess I'll start by doing over all my movies. I converted them to MPEGs the first time around. I guess I'll start over by setting up the projector, the camera and the conversion box again and this time making an AVI.

    Is AVI the best format to start with? Or should I do MPEGs? This software I have is supposed to let me do Hollywood-grade DVDs. Hard disk space isn't a problem as I have a 160-Gig drive on the way from California. It should be here on Wednesday or Thursday of next week.

    I'm not getting any more e-mail notifications. Anyone know why?
     
  8. MustBNuts

    MustBNuts

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    Okay, I've capture old 8mm film the way you are doing it....question: do you think the lighting effect is being caused by the converter box? You may want to change camcorder angles slightly to look for changes.

    Before I bought the converter box, though, I just put everything in a dark room, played the film onto the screen (pretty small, though) and trained my camcorder onto that picture...amazingly enough, the quality wasn't bad! (Mind you, the movies were from 1926!). I presume you are using an analog camcorder....?

    You want to capture as AVI. What editing software are you using? Maybe we can take a look at what filters come with your software...

    MBN
     
  9. Alex Ethridge

    Alex Ethridge Thread Starter

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    I have analog camcorder and a digital camera capable of capturing 30fps at 640 x 480.

    I am using the Kodak Moviedeck's built-in 4 x 5 screen. I do have a converter box, but, it would serve to only lessen the light intensity and require a wider aperture. Most lenses perform their best at medium apertures so I don't want to lessen the light intensity.

    The bright center is the product of two dynamics. One is that any camera lens has light fall-off at the edges, the wider the angle the more apparent. Then there is the inherent hot center on every projection device I've ever seen. Then multiply that by the light fall-off in the recording device and you have three steps of hot centers all multiplying each other.

    Some of the film is fairly evenly lit by soft light and the hot spot isn't so apparent; but, most of this film is of outdoor activity and there is a lot of it that has apparent bright centers and noticable light fall-off at the edges. I don't want to do this job but once so I want the best quality I can achive. Hence, the need for some way of evening the light across the plane.

    Editing software (I guess): VirtualDub, Ulead VideoStudio 7 SE, and DVD MovieFactory with something called Capture Wizard. I have some Pinnacle software here somewhere; but, I understand it is supposed to be pretty much junk.
     
  10. MustBNuts

    MustBNuts

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    I use Ulead Media Studio Pro...with pretty good results. You seem to be juggling two different issues: capture quality and original film quality.

    I don't know if you heard that "woooosssshhhh" sound as I read your last post...you seem to know a lot about photography - I won't even pretend to completely understand all you said.

    If you are looking for optimum quality, you may want to look into a professional outfit to do it for you (at least the initial capture and color balancing). If you want to do it at home, on your home equipment, there are certain limitations you will probably just have to cope with.

    I started trying the new "home" capture equipment back in 1995, and there's been a lot of improvement since then.

    Good luck finding what you're looking for.

    MBN
     
  11. Alex Ethridge

    Alex Ethridge Thread Starter

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    Well, I guess I do know a lot about photography that many don't know, nor do they need to these days.

    I bought my first camera in 1965 and I was very quick to learn. I got a job in a camera store when a 35mm, fully-manual camera was considered high-tech. I spent about all my earnings on film, processing and photo magazines. I was a semi-pro photojournalist for for several years in the 1980's and had one set of pictures published in People Magazine in a two-page, full-bleed spread and on 60 Minutes when it was the number-one, most-watched program on TV. If you ever see a People Magazine from 1985 with Ali McGraw on the front, open it up to the center spread and you'll see my credit adjacent to the picture. That same set was published in over 40 countries and netted over $38,000 after agent's fees.

    I learned when everything was manual. I had to set the aperture, shutter speed, and manual focus with a range finder. I also had to learn depth of field, manually calculate the strength of flash bulbs and the distance and then choose an aperture that would give proper exposere without going over the proper amount of light. Slide film was all I used and over exposing transpencies makes for a lot of washed out (read unrecoverable) information. Slide film and digital have that characteristic in common--err on the side of underexposure if you err at all.

    The highest speed color film in that day was Kodak Ektachrome (ASA) 160 (now known as ISO 160). But, mostly I shot Kodachrome (ASA) 25 and Kodachrome (ASA) 64.

    It has always been a fun hobby and a fun part-time income. Lots of good memories in that. I currently have a collection of personal slides numbering about 15,000 and that is my next conversion project after I get this job done.

    I got out of it almost entirely in 1995 when I quit doing weddings and I am beginning to get my feet wet in digital.
     
  12. Fredledingue

    Fredledingue

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    It's better to capture in avi. MPEG is already compressed and often badly compressed with capture.

    Everytime a video is compressed, you lose some quality. MPEG loses quiet a lot of quality.

    The best way is to capture in uncopressed avi. It takes UHGE amount of HD (like 20Mb/sec) but with 160 Gb, you can do it.

    With capture software, this software usualy let you chose avi, mpeg1 or mpeg2.
    As I said the best quality is with avi. When you have choosen avi, the software should let you chose between Uncompressed or a codecs from a list of codecs installed on your computer. Most of these codecs are very bad and you will want to download good codecs when you need them.

    Let's start with uncompressed video, now.
    The best softawre available to you now, are VirtualDub, Ulead VideoStudio 7 SE and AviUtl (see the link here: http://fullart.topcities.com/aviutl.htm ) Try all these 3.
    I think only Ulead will have the filter you need, but it's not sure.
    For Virtual Dub it will need some internet search to find it if it exists.
    For AviUtl, there is no such a filter as far as I know, but this program is realy fast and easy. I will look if there is no new AviUtl filters around.

    Once you open an avi file in one of these software, clic on the menus to see the offered tools and options. It's often faster than reading the helps but helps are helpfull too.
    It's nothing dramaticaly terroble to learn. Everybody starts one day! :)

    When you have made a project, and want to save it as avi, you have the choice of compressing it or leaving as uncompressed.
    Leave it as uncompressed if you want to work on it again later. Compress it if you want to put on some digital support (dvd, cd-rom etc)

    What's the end-support for your movies?
     
  13. Alex Ethridge

    Alex Ethridge Thread Starter

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    End product is distribution (to family) for playback on computers for now and eventually DVD set-top boxes.
     
  14. Fredledingue

    Fredledingue

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    To play on computers you will want to make an avi compressed into DivX
    http://www.divx.com

    DivX is not free or you must install the addware version (nothing terrible about that). They are both the same.
    There is also Xvid, free, but DivX is easier to use.

    Burn the divx avi to a normal data cd or data dvd.

    Calculate the bitrate with this free calculator
    http://clzm.veganismus.ch/
    It comes with useful newbie helps too.

    It's also useful to have Huffyuv, to make near lossless compression, a little bit more compressed than uncompressed, if your HD is to become full.
    http://neuron2.net/www.math.berkeley.edu/benrg/huffyuv.html

    It would be good to produce both divx avi files and dvd from the uncompressed file.
    You can always make a dvd from a divx but the quality is better from the uncompressed avi of course.

    To make dvd,

    More guides here

    http://www.doom9.org/index.html?/guides.htm
     
  15. MustBNuts

    MustBNuts

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    Just my two cents, but if you compress using DIVX, any computer running the movie will need to have the codec. If any of your users are like mine, just giving them a disk like that and expecting them to figure out that it's a codec issue, finding one, and installing it is purely wishful thinking....

    IMHO, stick with the standard/default codecs and if the movie is looking too big, just break it up into several and burn on multiple CDs. The benefit of this is that when it comes time to burn a DVD, you will already have multiple segments and creating a menu will be easy.

    MBN

    PS: if you haven't guess already, there are a million ways to do the same thing. It's really a matter of having all the facts, personal preference, and skill/technical savvy of your end user.
     
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