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Maximum FOV with 2X anamorphic lenses when cropped
  • B3GuyB3Guy

    Hey, all! Perhaps someone could do a quick test for me or maybe you already know . . .

    2X anamorphic lenses provide a very wide 3.55:1 aspect ratio when shooting in 16:9. When I get an anamorphic, I plan to have my final product be either 2.39:1 (or occasionally 2.75:1 if I'm feeling gutsy).

    I have found plenty of info on how wide of "taking" glass the various 2X anamorphic lenses can utilize without vignetting, but only when used at 3.5:1. (For example, a Kowa 8Z/16H in 3.55:1 is good down to a 35mm "taking" lens on GH2.)

    But if I'm cropping off the sides of my final product to 2.39:1, I would assume I should be able to use a bit wider of a taking lens, even if it vignettes on 16:9, as long as I'm able to crop out the vignette on the sides when trimming down to 2.39:1 from 3.55:1.

    What many people get excited with when thinking about anamorphic lenses (especially the 2X crop sensor GH2 crowd) is that the anamorphic gives a wider field of view. While this is true in the horizontal sense of the term, it is not true in the vertical sense. A 35mm taking lens with an anamorphic adapter on front may have twice the field of view horizontally, but vertically it is still a 35mm field of view (70mm equivalent on GH2). This doesn't really help you "get wider" for narrative work in which you are framing up people, where extra vertical field of view is what actually matters.

    If cropping 2X anamorphic footage down to 2.39:1 allows the use of an even slightly wider "taking" lens, then I would encourage anamorphic junkies out there to start experimenting with this strategy. even if you loos a bit of horizontal resolution, remember the footage still maintains full 1080 lines vertical, which will keep it looking sharp, even when stretched.

    Does anyone know how much more you gain when cropping like this? Using my example of a Kowa, could it be good down to 25mm with the sides cropped to 2.39:1?

  • 11 Replies sorted by
  • HillTop1HillTop1

    @B3Guy, I just recently bought a Kowa 2x and have being playing with it with an aim to achieved 2.39:1 like how you're saying. My problem is going from 3.55:1 to 2.39:1, I'm still fairly new with anamorphic so I will like to see what the experts say.

  • B3GuyB3Guy

    Well, you have to stretch the footage by 2X whatever you do, because the anamorphic is 2X. A good place to start would be setting your FCP sequence to your intended final resolution.

    (For 2.39:1, if you want to keep 1080 vertical resolution, the horizontal resolution would be 2580 wide. For the squish down method where the horizontal resolution stays at 1920, your vertical resolution would be 803, or maybe round off to 800.)

    Drop your clips in, then you "de-anamorphisize" I think by setting the aspect ratio of your clips to -100, or at least that's what I recall from some raw Sankor footage that my friend gave me to play around with.

    Then I would just adjust the scale of the clip until it just barely fills the whole 2.39:1 frame. the extra stuff hanging off the sides will not be visible.

    With full coverage lenses, I suppose this method also gives you some handles that you can "pan-scan" if need be. It'd be important when filming to mark somehow what will be chopped off so you can frame your shot accordingly.

    I think I understand this stuff in theory, but I don't have a pile of anamorphic adapters that I can actually test it out on. I'd love to hear from those of you with lenses on this subject . . . wether or not this crop yields significant advantages in the maximum vertical FOV department. I'm especially interested in the Kowas as they seem to be the most popular 2X south of expensive LOMOs.

  • kavadnikavadni

    What you are suggesting works.

    You have a anamorphic 2x squeezed image 1920 x 1080. You squish it vertically .. this gives you 1920 x 540 Then zoom in on it to get your desired height .. the edges go off screen Your after about 820px for 2.34 .. your zoom factor will be about 1.56 Which means about 1230 of your horizontal pixels remain

    Test the lenses .. lenses of same focal length vignette differently depending on brand and amount of light.

    You can probably estimate .. your chopping 30% of each side .. can you reduce your focal length by 30% .. I haven't tested and I doubt the math is that simple.

    If you take it all to 720P then the resolution junkies should be happy. 1230 px vs 1280 px. At 1920 it's like upscaling 720.

  • kavadnikavadni

    Couple of tips .. work in a 1920 x 1080 project, and crop at the time of output. Perform all colour correction, grading and noise reduction on the stretched footage, this gives your NLE more information to antialias and calculate colour values with.

  • HillTop1HillTop1

    So this's my finding from playing with it just now. I like these setting. (I am no expert, I deffer to you guys) I am using a canon FD 35mm F2 lens on Kowa 2x

    On FCP 7 sequence setting Frame size 1920x800, pixel aspect ratio: Square Scale: 140 Distort: upper LR, Lower RL (-960, -540; 960, -540; 960, 540; -960, 540) Aspect Ratio: -33 (if I do -100 even if I change distort values, it's way too squeezed) But those setting work great for me. FOV after the setting reduces just a bit not much to clear the vignetting.

    I also tried the 2580x1080 frame size with the above scale, distort and aspect ratio settings and it works great for me with same FOV.

    I am waiting to get a specially made lens clamp for the Kowa which the guy says will reduce vignetting.

  • itimjimitimjim

    It depends on the lens design too. Some 35mm will vignette, some wont. The best test I've found is to test stopped down with both lens and adapter focused to infinity. I'm able to get 2.39 out of Prominar 16H/8Z and Proskar 16 using a 35/2 Canon FD. Only my Bolex 32/16/1.5 can be used down to 28/2.

  • B3GuyB3Guy

    Well, I have my first anamorphic (Kowa 16-H) on its way. I'm sure I'll be keeping the Personal-View in the loop as I put it through its paces.

  • itimjimitimjim

    @B3Guy Have you got something to mount it with? I use the vidatlantic which does the job nicely, almost made for each other.

  • B3GuyB3Guy

    Made my own for now, I'll get a good one soon. The lens came, and I can report that as long as you're cropping to 2.39:1, the Kowa is good certainly down to 28mm. At least, it works with my 28mm f2.8 nFD lens. I have not tried 24mm, but I doubt it will be vignette-free that wide. Footage to come soon!

  • artiswarartiswar

    Bringing this back up as I have a 2x anamorphic on its way to me. Does shooting with a lens that vignettes a feasible solution for cropping 3.55 to 2.66 or less?

  • hellrazorhellrazor

    I found out that 24mm f2.8 Konica in 3:2 and 4:3 on GH4 covers. So you should be fine getting 2.4 out of it. Bad thing: the kowa distorts.

    passwort: konica24

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