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Author Topic: LCC to remove Vignetting?  (Read 822 times)

C+B

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LCC to remove Vignetting?
« on: December 10, 2015, 01:07:04 PM »

Hello!


I was wondering whether it's a good idea to use LCC to remove the vignetting of a lens. I noticed that my Mamiya 120mm macro produces more or less uneven vignetting, it's a bit more pronounced at the bottom of the image.
Should I use LCC to get rid of that or would that only really work if I stayed within the same distance (I think vignetting will get more pronounced the close I focus to an object)?

I know it's used to correct for using movements on a tech cam, but I was just wondering...
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Frederic_H

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Re: LCC to remove Vignetting?
« Reply #1 on: December 10, 2015, 01:13:16 PM »

Give it a try.

I do it with my 120 MF macro and other lenses too. The idea is to shoot the LCC in the exact same condition as your pic, as you point out the vignetting changes with the focusing distance (and the aperture, obviously).
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Paul2660

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Re: LCC to remove Vignetting?
« Reply #2 on: December 10, 2015, 01:22:25 PM »

Actually it's used to correct all light falloff/color cast.  So in your case, it would be no different than say, using a 28HR, or 32HR-W, with no CF on center with no movements.  Thus there will be some light falloff around the edges.  The LCC will correct for this very well, so I believe in your situation, the same should work also. 

The only difference, you have a 120mm macro, and C1 should have a correction for that built in.  But I agree, it's sure worth a quick try. 

Just make sure to keep the aperture constant, and if necessary change the shutter speed to allow more light in. 

Paul C
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C+B

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Re: LCC to remove Vignetting?
« Reply #3 on: December 10, 2015, 02:25:26 PM »

Well first of all thank you for your replies!

I did try to use the built-in corrections but for vignetting they did next to nothing... I'm getting the feeling that something is wrong with my flash sync setup, the lower part of the frame is noticeably darker than the rest - that initially lead me to believe that it's the lens that causes this effect and that's why I asked if it's possible to use LCC.
Now I'm not so sure, LCC works pretty well but it's still a bit dark...

But thank you! I'll definitely use it!
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Frederic_H

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Re: LCC to remove Vignetting?
« Reply #4 on: December 10, 2015, 03:07:09 PM »

It's probably a shutter/sync issue indeed.
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mediumcool

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Re: LCC to remove Vignetting?
« Reply #5 on: December 10, 2015, 08:26:24 PM »

How about posting a shot of a blank wall, slightly under-exposed?
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C+B

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Re: LCC to remove Vignetting?
« Reply #6 on: December 11, 2015, 09:05:57 AM »

So I took the shot and did some heavy curve adjustment to really show the issue, it's not _that_ bad in real life.
So this was synced at 1/125 and it really looks like there's something wrong... at 1/100 it looks much better but the 645DF+ should be able to get 1/125.
I even used the X-mode.

However it can't be an issue with the back because it works perfectly fine with the Leaf Shutter at 1/1600


edit: it might be my flash setup though.. Elinchrom RX 1200 / 600 synced with the old EL-Skyport. I guess I should rather use a cable or switch to another brand... :-/
« Last Edit: December 11, 2015, 09:12:47 AM by Christoph_B »
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Doug Peterson

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Re: LCC to remove Vignetting?
« Reply #7 on: December 11, 2015, 09:52:16 AM »

So I took the shot and did some heavy curve adjustment to really show the issue, it's not _that_ bad in real life.
So this was synced at 1/125 and it really looks like there's something wrong... at 1/100 it looks much better but the 645DF+ should be able to get 1/125.
I even used the X-mode.

However it can't be an issue with the back because it works perfectly fine with the Leaf Shutter at 1/1600


edit: it might be my flash setup though.. Elinchrom RX 1200 / 600 synced with the old EL-Skyport. I guess I should rather use a cable or switch to another brand... :-/

*Very* slight vignette from shutter is expected at X (1/125) mode using flash. If doing high accuracy work (eg art reproduction) you should use 1/100. For most normal commercial work X (1/125) is fine as the amount of vignette is very slight.

Do make sure to use X (1/125) though, not M (1/125) as it retimes things very slightly and amount of the slight vignette will be less.

C+B

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Re: LCC to remove Vignetting?
« Reply #8 on: December 11, 2015, 10:14:51 AM »

I know, that's why I use it in flash mode (X) - good to know this is normal, now I won't have to worry about the condition of the shutter or the sync mechanism - adopt, adapt and improve!

Thanks Doug!
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