Leaf Custom Gain Adjuster

[Streetwise]

Note: I had mistakenly posted this under DLSR and have moved it here to it's proper place.

I own an Aptus 65 back and have recently purchased a Cambo DS Wide for it. As for lenses, I've been renting from a large company in Chicago, but they only stock the Schneider Apo-Digitar XL lenses. After my first batch of wide images, I was disappointed to see an odd color shift in the images from one side of the frame to the other. I did some research and found out about the "lens cast" and "centerfold" phenomenon with shooting ultra-wide. A call to Leaf America put me on to a utility called the "Custom Gain Adjuster".

What I would like to know, is exactly how do you go about using this software? I could not find a users guide, but I may have just missed it. I did not get a white piece of plexiglass with my back. Would any old piece of white plexi work?

Secondly, according to Leaf's May 2007 Tech bulletin, "Leaf Aptus Backs and Ultra-Wide Angle Photography", they state that the lenses noted for causing the worst issues are the Schneider Apo-Digitar XL lenses. They suggest the Rodenstock Apo-Sironar digital HR lenses instead. Do you know who rents these lenses in the U.S.? The firm in Chicago does not.

As for "Best Practices", here are my questions:

- Do you typically create your custom gain files in the field, or after-the-fact, in the studio (via strobes)? If so, is it just a matter of writing down the aperture and V/H shift settings so they can be duplicated in the studio?
- If you produce gain files in the field, how would that work? It seems that if you were to put a piece of white plexiglass in front of the lens, it would eliminate most of the light.... So a 1 sec f/8 field exposure would produce a very dark (unusable?) gain exposure assuming a piece of plexi was put in front of the lens to create the gain file.

I'm just trying to understand how you personally go about shooting and applying the Custom Gain Adjustment to your files, and also what lenses you are using.

Thanks,

David Anderson

[pixjohn]

Do a search on LL for Leaf and gain utility and you will find lots of info.

1st you should call Rick Adshead at Leaf in NYC, or Ed Meyers at calumet where you got the camera.

2nd If you want to use the 24xl you have to shoot schneider. I believe you will still have to shoot the gain with the rodenstock lenses. You also get the benefit of correcting lens fall off.

3rd The gain is easy to shoot just call Rick and ask about the white disc or just shoot plain white plexi. You need to open 2 stop to get a correct exposure. I cheat and flash a strobe at the lens from 15 inches away.

Note: I had mistakenly posted this under DLSR and have moved it here to it's proper place.

I own an Aptus 65 back and have recently purchased a Cambo DS Wide for it. As for lenses, I've been renting from a large company in Chicago, but they only stock the Schneider Apo-Digitar XL lenses. After my first batch of wide images, I was disappointed to see an odd color shift in the images from one side of the frame to the other. I did some research and found out about the "lens cast" and "centerfold" phenomenon with shooting ultra-wide. A call to Leaf America put me on to a utility called the "Custom Gain Adjuster".

What I would like to know, is exactly how do you go about using this software? I could not find a users guide, but I may have just missed it. I did not get a white piece of plexiglass with my back. Would any old piece of white plexi work?

Secondly, according to Leaf's May 2007 Tech bulletin, "Leaf Aptus Backs and Ultra-Wide Angle Photography", they state that the lenses noted for causing the worst issues are the Schneider Apo-Digitar XL lenses. They suggest the Rodenstock Apo-Sironar digital HR lenses instead. Do you know who rents these lenses in the U.S.? The firm in Chicago does not.

As for "Best Practices", here are my questions:

- Do you typically create your custom gain files in the field, or after-the-fact, in the studio (via strobes)? If so, is it just a matter of writing down the aperture and V/H shift settings so they can be duplicated in the studio?
- If you produce gain files in the field, how would that work? It seems that if you were to put a piece of white plexiglass in front of the lens, it would eliminate most of the light.... So a 1 sec f/8 field exposure would produce a very dark (unusable?) gain exposure assuming a piece of plexi was put in front of the lens to create the gain file.

I'm just trying to understand how you personally go about shooting and applying the Custom Gain Adjustment to your files, and also what lenses you are using.

Thanks,

David Anderson
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[Prakash Patel]

As for "Best Practices", here are my questions:

- Do you typically create your custom gain files in the field, or after-the-fact, in the studio (via strobes)? If so, is it just a matter of writing down the aperture and V/H shift settings so they can be duplicated in the studio?
- If you produce gain files in the field, how would that work? It seems that if you were to put a piece of white plexiglass in front of the lens, it would eliminate most of the light.... So a 1 sec f/8 field exposure would produce a very dark (unusable?) gain exposure assuming a piece of plexi was put in front of the lens to create the gain file.

I'm just trying to understand how you personally go about shooting and applying the Custom Gain Adjustment to your files, and also what lenses you are using.

Thanks,
David Anderson
[a href=\"index.php?act=findpost&pid=138662\"][{POST_SNAPBACK}][/a]
[/quote]

David

Shooting the gain files can be done very simply. (or LCC-Phase or WhiteReference-Sinar,Hassy has some sort of a  solution...can't comment , have not used the Hassy backs on view cameras)
My work flow whether shooting tethered in Leaf V8 or to a card is very simple;
I shoot a gain file for every new camera position with a piece of white plexiglass in front of the
lens. Typically it is about +2 fstop....... the exposure of this gain file is centered in the histogram.
This grayish gain file is saved in the shoot folder and visually separates ( like a bookmark) all the different camera positions.
Use the Custom Gain Adjuster utility to apply these grayish gain files to your selects ( this creates
a new set of raw files with the color/density anomalies addressed in a different folder than the original captures.....in this way you have the original capture as well as the new adjusted raw) and process to your liking in your preferred raw developer.  Pretty straight forward workflow wise and very effective if you shoot a camera with lens movements.

You can think of these files as custom profiles or an optical  pixel map  that takes into account non axial lens movements as well as specific lighting anomalies. The Leaf and the Sinar solutions address both density and color "casts", currently Leaf has a further ability to control the inherent optical vignetting with a 0-100% slider. I think the Phase solution addresses only the color casts, however their tethered solution allows you to view on the laptop corrected jpg previews......nice feature for when an art director is peeking at the laptop, but pretty useless for an ultrawide angle interior shooter that needs to see a preview with the lens vignette density
corrected so he or she can figure out what needs to be lit.

Hint, Hint Leaf, Sinarand Hassy....please have a tethered solution that allows the photographer to see files with the density anomalies corrected on the laptop wihtout redesigning or not supporting the current solutions.
Hopefully Thierry, Yair, and Steve Hendrix can eloborate whats brewing........I am sure we will have to have our money ready for the next upgrade/update

Currently, the Leaf gain adjuster is a separate utility and is not incorporated with V11 software......I think this is great!
It is a little clunkier to use but the upside is that you get raw files with anomalies/color casts removed and a custom controlled lens vignette density ready to be processed in the soup of your choice...........Leaf V11, LightRoom, ACR, Raw developer........

regards

[Dustbak]

Prakash,

I understood you have to put appr. 2 stops of light more on the custom gain shots. I never took the time to actually start using custom gain but I was under the impression you could not open your lens because you had to keep the same aperture as the shots that you want to correct?

So you either have to set shutter speed slower or have strobes put out 2 stops more light.

Since I work mostly in studio which is totally dark for me it is no use setting a slower shutter speed.

My strobes are not powerful enough to give me 2 more stops. These are the primary reasons I never bothered putting a lot of time in custom gain.

Do I read correctly that you can open up your lens 2 stops even if that is not the aperture that you will be using in the actual shots??

[thsinar]

Sorry if I answer for Prakash!

NO, you cannot open the aperture: you HAVE TO use the same f-stop as your actual image on which this shading should be applied, otherwise the shading will be wrong.

Best regards,
Thierry

Do I read correctly that you can open up your lens 2 stops even if that is not the aperture that you will be using in the actual shots??
[a href=\"index.php?act=findpost&pid=138794\"][{POST_SNAPBACK}][/a]

[pixjohn]

It takes a few step but I just shoot the Gain in V8 and upload the file to the back. I then shoot my images in V10. I am going to try V11.2 since it now works with V8. I just use a simple $35 mini strobe screwed into a socket pointed directly at the lens approximately 15 inchs away.

[Dustbak]

Sorry if I answer for Prakash!

NO, you cannot open the aperture: you HAVE TO use the same f-stop as your actual image on which this shading should be applied, otherwise the shading will be wrong.

Best regards,
Thierry
[a href=\"index.php?act=findpost&pid=138796\"][{POST_SNAPBACK}][/a]

That is what I thought as well. Thanks Thierry.

[Dustbak]

It takes a few step but I just shoot the Gain in V8 and upload the file to the back. I then shoot my images in V10. I am going to try V11.2 since it now works with V8. I just use a simple $35 mini strobe screwed into a socket pointed directly at the lens approximately 15 inchs away.
[a href=\"index.php?act=findpost&pid=138806\"][{POST_SNAPBACK}][/a]

How do you determine how much you flash into the lens? Guestimation? Doesn't it alter the scene/elements that need to be corrected (different cast and light fall of because of the additional light)?

[rainer_v]

Prakash,

I understood you have to put appr. 2 stops of light more on the custom gain shots. I never took the time to actually start using custom gain but I was under the impression you could not open your lens because you had to keep the same aperture as the shots that you want to correct?

So you either have to set shutter speed slower or have strobes put out 2 stops more light.

Since I work mostly in studio which is totally dark for me it is no use setting a slower shutter speed.

My strobes are not powerful enough to give me 2 more stops. These are the primary reasons I never bothered putting a lot of time in custom gain.

Do I read correctly that you can open up your lens 2 stops even if that is not the aperture that you will be using in the actual shots??
[a href=\"index.php?act=findpost&pid=138794\"][{POST_SNAPBACK}][/a]

with sinar you should not have problems with non-shiftable lenses because the centerfold is removed "on the fly" in any case. the white shots have nothing to with this.
i suppose you speak from "normal" mf lenses? in this case you should be able to shoot one white reference profile at a middle aperture and use that for the whole shooting.

[yaya]

How do you determine how much you flash into the lens? Guestimation? Doesn't it alter the scene/elements that need to be corrected (different cast and light fall of because of the additional light)?
[a href=\"index.php?act=findpost&pid=138825\"][{POST_SNAPBACK}][/a]

Ray,

The diffuse filter, as its name states, is strong enough to eliminate any variations of light coming from different directions.

The filter takes about 2 stops off the exposure so you will have to compensate by using a lower shutter speed or by throwing more light in, like John does. The purpose of this is to reduce any noise coming from an under exposed image.

All back manufacturers use a similar technique, more or less.

This process is planned to be implemented into LC11 in one of the coming versions, most likely before the end of this year.

In the meantime (for Prakash), what I do is setting LC11 (or any other converter) to watch the folder with the corrected files, including different versions with different vignetting adjustments, if needed.
I can use the finder for sorting/ naming the gain files and the to-be-corrected RAW files, so clients only see the "proper" images.

I hope this helps

Yair

[adammork]

One real advantage with the Leaf Custom Gain Adjuster is that if you expose the gain file right after the real exposes, without removing the back, it "removes" the dust spots in the process, so you end up with a clean file.

It will be fine with the gain adjuster in LC11, but please still provide the Custom Gain Adjuster as a stand alone application, so we can use the developer by our choice - it's great with that kind of flexibility.
 
 
 /Adam

[Streetwise]

It takes a few step but I just shoot the Gain in V8 and upload the file to the back. I then shoot my images in V10. I am going to try V11.2 since it now works with V8. I just use a simple $35 mini strobe screwed into a socket pointed directly at the lens approximately 15 inchs away.
[a href=\"index.php?act=findpost&pid=138806\"][{POST_SNAPBACK}][/a]

I'm not sure I understand why you shoot your Gain in V8? Isn't a gain file basically just another exposure with the diffuser and +2 EI?


Dave

[yaya]

I'm not sure I understand why you shoot your Gain in V8? Isn't a gain file basically just another exposure with the diffuser and +2 EI?
Dave
[a href=\"index.php?act=findpost&pid=138840\"][{POST_SNAPBACK}][/a]

Dave hi,

V8 allows you to create a custom gain file that can be loaded into the back when tethered to either V8 or LC11. It sits under Camera>Calibration>Gain. You can store a library of these files and load them as required, so as you shoot the images come up corrected for casts and falloff.
A simplified version of this process is going to be implemented into LC11 in the near future.

Yair

[thsinar]

Dear Prakash,

there is a tethered solution for SB eMotions, with the Brumbaer Tools.

The workflow for applying the "white shadings" is even faster and simplier than for any other application: all you have to do is to shoot your shadings before your actual image. This shading will be AUTOMATICALLY applied to the right image file by the application. You don't have to bother about "which shading corresponds to which image"! And this can even be done in batch process, on entire image folders of as many images you wish.

Also, the RAWs are ALWAYS kept and the "shaded" images are saved separately.

Best regards,
Thierry

Hint, Hint, Sinar....please have a tethered solution that allows the photographer to see files with the density anomalies corrected on the laptop wihtout redesigning or not supporting the current solutions.
Hopefully Thierry can eloborate whats brewing........
Currently, the Leaf gain adjuster is a separate utility and is not incorporated with V11 software......I think this is great!

regards
[a href=\"index.php?act=findpost&pid=138790\"][{POST_SNAPBACK}][/a]

[pixjohn]

I always have a finished captured file with no post production correction needed. The V8 software takes about 4-5 min to do the gain file. The Gain Adjuster stand alone takes about 30 sec on location and a few min in post.  Another reason is lighting, If you use the gain in v8 you see a finished image, If you use the gain adjuster in post it can alter the lighting effect I want.  

I'm not sure I understand why you shoot your Gain in V8? Isn't a gain file basically just another exposure with the diffuser and +2 EI?
Dave
[a href=\"index.php?act=findpost&pid=138840\"][{POST_SNAPBACK}][/a]

[pixjohn]

I guesstimate my starting point, but the software will tell me if I am to bright or dark.

How do you determine how much you flash into the lens? Guestimation? Doesn't it alter the scene/elements that need to be corrected (different cast and light fall of because of the additional light)?
[a href=\"index.php?act=findpost&pid=138825\"][{POST_SNAPBACK}][/a]

[rainer_v]

I always have a finished captured file with no post production correction needed. The V8 software takes about 4-5 min to do the gain file. The Gain Adjuster stand alone takes about 30 sec on location and a few min in post.  Another reason is lighting, If you use the gain in v8 you see a finished image, If you use the gain adjuster in post it can alter the lighting effect I want.
[a href=\"index.php?act=findpost&pid=138938\"][{POST_SNAPBACK}][/a]

on which machine it takes 4-5 minutes?

[pixjohn]

It takes 8 shots to create the Gain file in V8. from start to Finnish upload to the back. I use a 17 inch macpro. I am hoping the V11 will only take 1 shot like the stand alone gain adjuster.

on which machine it takes 4-5 minutes?
[a href=\"index.php?act=findpost&pid=138942\"][{POST_SNAPBACK}][/a]

[Prakash Patel]

In the meantime (for Prakash), what I do is setting LC11 (or any other converter) to watch the folder with the corrected files, including different versions with different vignetting adjustments, if needed.
I can use the finder for sorting/ naming the gain files and the to-be-corrected RAW files, so clients only see the "proper" images.

Yair
[a href=\"index.php?act=findpost&pid=138833\"][{POST_SNAPBACK}][/a]

Yair

Sorry for the geeky inquiry...........can you please explain this in more detail.
for tethered shooting, are you saying that there is some sort of script that automatically  applies the identified gain file to the subsequent image files and exports the corrected file to a watched folder in Leaf Capture 11? So while you are shooting and refining lighting you can see the last shot with the gain file applied automatically? Is this some sort of a work around for the upcoming tethered feature that you mentioned?

[yaya]

Yair

Sorry for the geeky inquiry...........can you please explain this in more detail.
for tethered shooting, are you saying that there is some sort of script that automatically  applies the identified gain file to the subsequent image files and exports the corrected file to a watched folder in Leaf Capture 11? So while you are shooting and refining lighting you can see the last shot with the gain file applied automatically? Is this some sort of a work around for the upcoming tethered feature that you mentioned?
[a href=\"index.php?act=findpost&pid=138977\"][{POST_SNAPBACK}][/a]

No nothing that clever...

I set 3 Shots folders:

1. Captured images
2. Diffused files
3. Corrected files

LC11 is set to view #3 while I shoot into #1 and #2 and get the Custom Gain Adjuster to correct #1 using the files from #2.
If further fine tuning of the falloff is required I can always go back and re-adjust.

Hope this clarifies

Yair