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Thread: Centre filter or LCC to correct fall off in tech cams

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    Centre filter or LCC to correct fall off in tech cams

    I noticed quite a bit of noise in my shifted files taken with the HR32 Rodenstock ( on an IQ180) I was wondering what the verdict is out there:
    Is it worth getting the Centrefilter to improve file quality or is C1s LCC fall off feature doing the same ( sometimes noisy) job?
    I would also consider this centre filter for the 43 XL but the increase in exposure time especially in darker light plus having to shoot the LCC does cost too much time outdoors when light is changing fast at dusk or dawn
    But corner noise is an issue when the lens is shifted
    Thanks
    Grischa

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    Administrator Bob's Avatar
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    Re: Centre filter or LCC to correct fall off in tech cams

    The center filter is important for any lens where the falloff is more than a stop or two as the amount of boost that lcc falloff correction needs to do effectively pulls the file that many stops.
    To keep noise down then a center filter is very much recommended, but you need the right one.
    Another consideration, is that come center filters seems to be very prone to flare, and care must be taken to shade them completely.
    -bob

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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Centre filter or LCC to correct fall off in tech cams

    I just bought one for my 35XL and still playing around with it but the center filter seems to help a great deal it is like a 2 stop falloff and the corners do vignette pretty heavy. I shot a interior industrial job yesterday with strobe and available light and it was very useful as everything was even across the frame. I think on the 180 it is probable wise to use one since we all know some of the movement restrictions with it. Its certainly helping my 160 and with or without the LCC i am getting really nice evenness across the image. Personally i like a little vignette but i want to control that on my end and add if i want.

    I'm still playing around with this so after some more shooting I will have a better feel for it. I have not taken it outside yet with the center filter except for a couple sky shots but they where very even across the sky. So I'm going to use it. Just FYI i will have a 32 next week to use at my disposal so we will see but given that wide a lens and the 180 I would tend to think it would certainly help and also may pick up more shifting as the falloff will be less. That is worth a test to see where your falloff limit starts and stops with it and with out it. But my gut feeling is your better off with it.

    BTW yesterday I adjusted my ISO some for balancing my scene so i could hold the aperture I wanted to use. The 180 you can certainly go ISO 100 and be in excellent shape. I was shooting 1 to 1.5 second exposures inside with mixing strobe and available light. Unfortunately I can't show these images as they are military related.

    I do certainly want to do more testing to feel more comfortable about my shooting process with this lens. I will say this the damn images are killer in detail, glad i bought the tech cam.
    Photography is all about experimentation and without it you will never learn art.

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    Re: Centre filter or LCC to correct fall off in tech cams

    Well you know the story. He COULD show us, but then he'd have to kill us.

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    Re: Centre filter or LCC to correct fall off in tech cams

    Thanks for the replies,
    I wanted to share this screen shot that shows 2 uncorrected LCCs of the same shot. The top one shot without a Centre filter the bottom one with a Centre filter. Lens Rodenstock 32HR with 15mm horizontal shift in landscape mode on an IQ180 full frame back. Both images at f:11
    Obviously the 15mm are a stretch for this lens on a full frame sensor but it shows clearly as all of you correctly stated earlier that there is quite a bit of "help" coming form the Centre Filter when it comes to LCC lens cast correction.

    On the other hand I found with this particular lens that it does not make much of a different when the lens is not shifted.
    This particular CF is marked for 1.5 exposure correction. I think its closer to 3-5X instead of 1.5 for exposure compensation

    On another note I heard that Schneider is soon releasing the CF for the 43XL that many folks have been waiting for. Cant wait!

    Grischa

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    Re: Centre filter or LCC to correct fall off in tech cams

    keep in mind that using a CF, you are loosing F stops... with the limitation of MFDB for long exposure... at dusk it can be impossible to achieve the correct exposure !

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    Re: Centre filter or LCC to correct fall off in tech cams

    I used the CF on the HR 32 yesterday to shoot interior in a mall and I got just 5 sec at f 8 at 32 ISO.
    I rarely get over 30 sec exposure
    The real problem IMO is the LCC duration when shooting at dusk which makes it impossible to stitch due to the change in hues between exposures

    G
    Quote Originally Posted by archivue View Post
    keep in mind that using a CF, you are loosing F stops... with the limitation of MFDB for long exposure... at dusk it can be impossible to achieve the correct exposure !

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    Re: Centre filter or LCC to correct fall off in tech cams

    Have you considered raising the ISO just to shoot the LCC frames? I realize you'll be introducing noise to the LCC images but for the LCC correction that may or may not be significant vs the overall color cast/fall off.

    I'm sure Doug or someone else can comment on the ISO noise impact ...
    Remember: adventure before dementia!

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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by GrahamWelland View Post
    Have you considered raising the ISO just to shoot the LCC frames? I realize you'll be introducing noise to the LCC images but for the LCC correction that may or may not be significant vs the overall color cast/fall off.

    I'm sure Doug or someone else can comment on the ISO noise impact ...
    Quality impact on correcting light fall off will be negligible. Impact on correcting color will be minor. Impact on correcting dust with be strong.

    It's also acceptable to use a diffused light source like a pocket flashlight to illuminate the LCC panel from the front. Of course you'd want to be sure to illuminate it evenly. The further the source of light, and the more the diffused the source of that light the more diffused across the surface of the LCC the source light will be.

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    Re: Centre filter or LCC to correct fall off in tech cams

    "Centre filter or LCC to correct fall off in tech cams"

    Both (at the same time)

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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by GrahamWelland View Post
    Have you considered raising the ISO just to shoot the LCC frames? I realize you'll be introducing noise to the LCC images but for the LCC correction that may or may not be significant vs the overall color cast/fall off.

    I'm sure Doug or someone else can comment on the ISO noise impact ...
    I tech cam stitch about 90% of the time and I shoot LCCs for every shot, so about half my file storage goes to gray nothingness. I was thinking that "QII S" might help out here. Will having the original shot and the LCC differ in file format have any negative effects on the quality of the correction?

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    Re: Centre filter or LCC to correct fall off in tech cams

    doug:

    very interesting about using an alternative light source to reduce the shutter speed, but isn't the nature of the light a critical ingredient for color cast correction? or is it enough to simply have the light be diffuse and uniform?

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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by jlm View Post
    very interesting about using an alternative light source to reduce the shutter speed, but isn't the nature of the light a critical ingredient for color cast correction? or is it enough to simply have the light be diffuse and uniform?
    The nature of the lighting in the scene is NOT important for LCC correction. That's why in fact you use an LCC panel, so you're seeing a mapping of the color produced by the lens/back interaction rather than a mapping of the scene color. It is important that you illuminate the panel in a diffused and uniform way (think at the extreme of only shining a hard flashlight at the left half of the panel - the back would interpret the darker half of the LCC panel as meaning that side of the image was suffering from lens fall off).


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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by alan_w_george View Post
    I tech cam stitch about 90% of the time and I shoot LCCs for every shot, so about half my file storage goes to gray nothingness. I was thinking that "IIQ S" might help out here. Will having the original shot and the LCC differ in file format have any negative effects on the quality of the correction?
    That's a very good question! I don't know! Everything in the logic of it says that would be fine to do, but having not tested it myself I cannot say for 100%.

    Quick note: it is IIQ not QII. It stands for Intelligent Image Quotiant - not that this makes it easier to remember!

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    Re: Centre filter or LCC to correct fall off in tech cams

    i definitely get it, but why are jack and others taking so many lcc shots...like one per image? sounds like they could simply make a catalog for different apertures, shifts, etc, in the studio with a glass of Hendrick's, like i am sipping right now, with a splash of bitters

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    Re: Centre filter or LCC to correct fall off in tech cams

    In the long term, having a LCC frame just before or after every shot, is more convenient and less prone to errors than writing down every picture setup ( focal, shift amount, focus distance and so on )

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    Senior Member etrump's Avatar
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    Re: Centre filter or LCC to correct fall off in tech cams

    It also is an easy way to remove sensor dust.

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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by dougpetersonci View Post
    Quick note: it is IIQ not QII. It stands for Intelligent Image Quotiant - not that this makes it easier to remember!
    Oops, that must be my dyslexia showing:)

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    Re: Centre filter or LCC to correct fall off in tech cams

    Quote Originally Posted by jlm View Post
    i definitely get it, but why are jack and others taking so many lcc shots...like one per image? sounds like they could simply make a catalog for different apertures, shifts, etc, in the studio with a glass of Hendrick's, like i am sipping right now, with a splash of bitters
    The problem is taking notes on each shot is it is too error prone and a pain in the ***. I have always thought a little note recording feature on the back (like the 1DsIII has) would definitely change my workflow for the better. It's easier (for me) to just shoot an LCC for every shot. Plus the LLC can act as a backup WB if you use a neutral filter.

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