Technique for lcc correction for lenses with extreme light falloff

[Boinger]

Hi I am curious how do you handle LCC corrections for lenses with extreme light falloff.

I have a Schneider 28XL and I dont have a center filter for it. So what is the best way to lift the corners while correcting the image for lcc as well?

I guess I am not clear on how to exposure blend with an lcc correction.

 

[Alkibiades]

Hi I am curious how do you handle LCC corrections for lenses with extreme light falloff.

I have a Schneider 28XL and I dont have a center filter for it. So what is the best way to lift the corners while correcting the image for lcc as well?

I guess I am not clear on how to exposure blend with an lcc correction.

what software do you use?

 

[Paul Spinnler]

Hi I am curious how do you handle LCC corrections for lenses with extreme light falloff.

I have a Schneider 28XL and I dont have a center filter for it. So what is the best way to lift the corners while correcting the image for lcc as well?

I guess I am not clear on how to exposure blend with an lcc correction.

Do you have an IQ4?

In my experience you need to work very carefully and have the right sensor to be able to fully correct the 28 XL.

I make sure to use raw histogram and to expose the LCC shot to peak in the middle of the histogram.

The CF helps, but it also works without CF on the IQ4 if you are very diligent with the exposure to not clip highlights and have enough information in the shadows to be able to lift them via LCC.

Again, mileage may vary if you do not own an IQ4.

Fantastic lens.

 

[mdshaw]

I have this lens & also the CF filter fo fit. I hardly ever use the CF because I mostly shoot interiors & need all the flash power I can get. For me, LCC handles the light fall off very well, even with a +10 shift (when processed in C1).

Matthew

 

[dchew]

In Capture One, the LCC correction includes light falloff that you can adjust in percentage. Although I don't have the 28, this works fine with the 35xl. You do have to check the box "Enable Uniform Light." I don't have to to anything else in regards to light fallofff. I do sometimes have to fix tiling issues though.

I've used it with the IQ180, 3100 and 4150.

Dave

 

[Boinger]

I do have an iq4. I am shooting interiors as well and the corners just get way too dark. So when I use the lcc it adds quite a lot of noise in the corners.

Was trying to clean that up a bit. I am not using flash so maybe that is something I have to consider.

 

[jng]

I do have an iq4. I am shooting interiors as well and the corners just get way too dark. So when I use the lcc it adds quite a lot of noise in the corners.

Was trying to clean that up a bit. I am not using flash so maybe that is something I have to consider.

Can you use (or are you using) Dual Exposure+ on the IQ4 to help minimize noise when you apply the LCC correction?

John

 

[Boinger]

Can you use (or are you using) Dual Exposure+ on the IQ4 to help minimize noise when you apply the LCC correction?

John

I tried experimenting with that but I am not sure if I should do the lcc in dual exposure as well? or Just the image with dual exposure than apply a normal lcc file.

 

[jng]

I tried experimenting with that but I am not sure if I should do the lcc in dual exposure as well? or Just the image with dual exposure than apply a normal lcc file.

I hadn't considered that! But I would think that the latter if not both approaches should work. Bottom line is whether you get better results that don't look unnatural. As @dchew mentioned above, you can adjust the % correction for light falloff in C1.

 

[Paul Spinnler]

I do have an iq4. I am shooting interiors as well and the corners just get way too dark. So when I use the lcc it adds quite a lot of noise in the corners.

Was trying to clean that up a bit. I am not using flash so maybe that is something I have to consider.

Use frame averaging to lower noise floor and expose for highlights ... ie work carefully with the raw histogram. LCC plate peaking at 127, ie expose for absolute neutrality

 

[Boinger]

Use frame averaging to lower noise floor and expose for highlights ... ie work carefully with the raw histogram. LCC plate peaking at 127, ie expose for absolute neutrality

What do you mean by LCC plate peaking?

 

[dchew]

I tried experimenting with that but I am not sure if I should do the lcc in dual exposure as well? or Just the image with dual exposure than apply a normal lcc file.

I've always just done a std exposure when creating an LCC after either DE+ or FA. As for whether to use FA or DE+, I did an early test right when they came out, and got clearly lower noise with DE+. But it was a relatively small number of FA images. I suppose at some point that should theoretically flip and FA would be equal or better. Regardless, either one would be a significant improvement over a single straight image.

Dave

Edit: Here was that original test: Dual Exposure Plus

 

[Paul Spinnler]

What do you mean by LCC plate peaking?

The LCC is one colour. Even, but with some vignetting. It will sharply peak in the histogram given the more or less uniform image information, so make sure the exposure peak is smack in the middle. C1 may of course also adjust a non perfect LCC, but with the 28 XL you have a more complex vignetting so I typically make sure to expose it carefully.

Some people also have a workflow: 2 stops faster with the LCC plate in front of the lens than the scene exposure.

 

[tcdeveau]

Sometimes i use gradient or radiant filters if needed to adjust for light falloff when I don’t an LCC

 

[diggles]

The LCC is one colour. Even, but with some vignetting. It will sharply peak in the histogram given the more or less uniform image information, so make sure the exposure peak is smack in the middle. C1 may of course also adjust a non perfect LCC, but with the 28 XL you have a more complex vignetting so I typically make sure to expose it carefully.

Some people also have a workflow: 2 stops faster with the LCC plate in front of the lens than the scene exposure.

@Boinger - I almost always use the heatmap exposure evaluation tool instead of the histogram. When shooting the LCC exposure I try to keep the brightest areas of the heatmap green, which to Paul's point is 50% gray.

 

[Boinger]

The LCC is one colour. Even, but with some vignetting. It will sharply peak in the histogram given the more or less uniform image information, so make sure the exposure peak is smack in the middle. C1 may of course also adjust a non perfect LCC, but with the 28 XL you have a more complex vignetting so I typically make sure to expose it carefully.

Some people also have a workflow: 2 stops faster with the LCC plate in front of the lens than the scene exposure.

I see i am definitely not getting a sharp peak in the histogram its more like a large plateau. I have tried quite a large range of LCC exposure settings and they all seem to yield similar results.

@Boinger - I almost always use the heatmap exposure evaluation tool instead of the histogram. When shooting the LCC exposure I try to keep the brightest areas of the heatmap green, which to Paul's point is 50% gray.

I had no idea this feature existed I had to go look it up in the iq4 manual. I am definitely going to be trying that out next time I am out to shoot.

I am attaching a screenshot of my c1 window with the some lcc shots.

 

[Paul Spinnler]

It looks normal for the complex vignetting pattern of the 28 XL; your histogram is within the dynamic range of the sensor; do you use the official LCC plate from phase one? It has a specific translucence and thickness which may have an impact.

Still, it looks like the contrast is too high for C1 to do a perfect correction on the basis of the specific LCC plate you have - it doesn’t fully correct the light falloff in the corners. Maybe try to expose the LCC more to the right? The background scene may also play a role …

 

[Paul Spinnler]

@Boinger - I almost always use the heatmap exposure evaluation tool instead of the histogram. When shooting the LCC exposure I try to keep the brightest areas of the heatmap green, which to Paul's point is 50% gray.

Didn’t know about the heatmap; that’s a candidate for the next firmware.

 

[dchew]

I see i am definitely not getting a sharp peak in the histogram its more like a large plateau. I have tried quite a large range of LCC exposure settings and they all seem to yield similar results.

I had no idea this feature existed I had to go look it up in the iq4 manual. I am definitely going to be trying that out next time I am out to shoot.

I am attaching a screenshot of my c1 window with the some lcc shots.

When you have a lot of color cast and vignetting, you will get a big plateau like that. I would target a slightly brighter exposure. I actually push it to the right a bit and don't target the center but the right half of the histogram. In the heat map function, I target yellow with some red and some green/blue. As long as your center is not blown out, I think the brighter the better. BTW, I love the heat map and trust it more than the histogram. Maybe not "trust," but I have learned to interpret it more reliably.

As Paul suggested, I usually add 2 stops to the LCC by default. Another trick I do sometimes is to swing the camera around to a brighter light source like in the sun's direction or brighter sky. Then I can get away with not adjusting the exposure to get a brighter LCC.

Dave

 

[diggles]

I had no idea this feature existed I had to go look it up in the iq4 manual. I am definitely going to be trying that out next time I am out to shoot.

Me either until @dchew suggested I try it. Haven't looked back since!