ExpoDisc and UV Filter not a good match?

[DrTebi]

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Hello,

 

I have just received the ExpoDisc Neutral White Balance Filter, and did a few test shots in my living room. The shots came our really nice, and compared to the AWB, much better. However, I realized I did not have the UV Filter on the lens, and repeated my test shots with the UV filter on (setting the Manual White Balance again, of course). But now the results were off--at least in my opinion.

 

So I went on and set up a little "known objects" table and did five different shots to examine the white balance qualities. My light source is our skylight, which has a "milky" surface, and today is a sunny day here in San Francisco. So you could say the light is a pretty nice warm light... As noted in the manual for the ExpoDisc, I pointed the camera at the light source from the subject's view when taking the white balance through the ExpoDisc.

 

The shots below were taking like so:

 

1) AWB without UV filter, shot taken without UV filter

2) AWB with UV filter, shot taken with UV filter

3) Manual WB without UV filter, shot taken without UV filter

4) Manual WB with UV filter, shot taken with UV filter

5) Manual WB without UV filter, shot taken with UV filter

 

To me, number 3 and maybe number 5 have the best natural colors.

 

What do you think? Has anybody experienced similar problems?

 

 

P.S.: Yes, the beer is empty, but I didn't drink that today

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[GarethC]

never tried it but I will depending on hte responses to this thread. to me 4 looks easily the worst and if I'm reading it correctly, it should be the best?

[Jamie Roberts]

What lens are you using? Is it coded and was the coding on in the firmware?

[DrTebi]

I am using a brand new the Leica 28mm Elmarit ASPH. So yes, it does have the coding, and the setting on the camera is set to "Lens Detection: On + UV / IR"

 

Does this have something to do with it? Should I have this off when doing manual WB shots with the UV filter off? I am a bit confused about this setting.

[stevelap]

Just got an ExpoDisc to use with an SLR. Haven't used it with the M8 yet, but seem to remember reading elsewhere on the forum that others had used it with favourable results.

[Jamie Roberts]

I am using a brand new the Leica 28mm Elmarit ASPH. So yes, it does have the coding, and the setting on the camera is set to "Lens Detection: On + UV / IR"

 

Does this have something to do with it? Should I have this off when doing manual WB shots with the UV filter off? I am a bit confused about this setting.

 

No--I was just curious; it's so hard to tell anything about the workings of a camera on the 'net. The file doesn't even have a profile attached to it, so I'm assuming it's sRGB, too. Is this an in-camera JPEG? Or did you use a RAW conversion?

 

So making that colour space assumption, number 4 has all the obvious neutrals in the center very close to neutral, but it still looks a very little bit green around the edges, or a bit over-corrected for the wide vignette (which is cyan without a filter and without correction by the camera). Number 5 measures the closest to neutral, so I'm thinking there's an issue with the way you produced the shot...

 

So the next obvious question is are you using an actual Leica branded UV / IR filter or someone else's?

[DrTebi]

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No--I was just curious; it's so hard to tell anything about the workings of a camera on the 'net. The file doesn't even have a profile attached to it, so I'm assuming it's sRGB, too. Is this an in-camera JPEG? Or did you use a RAW conversion?

 

So making that colour space assumption, number 4 has all the obvious neutrals in the center very close to neutral, but it still looks a very little bit green around the edges, or a bit over-corrected for the wide vignette (which is cyan without a filter and without correction by the camera). Number 5 measures the closest to neutral, so I'm thinking there's an issue with the way you produced the shot...

 

So the next obvious question is are you using an actual Leica branded UV / IR filter or someone else's?

 

Yes, I am using a Leica UV Filter, it's also brand new.

 

I used RAW and sRGB, and then loaded the images into Lightroom with LR's default conversion. The export was done as a JPG quality 70 sRGB.

 

I realize there could be more issues like the processing of the RAW file. However, WB looks great when shooting with the ExpoDisc and no UV filter when checking on the monitor of the camera already, and looks incorrect when doing the same with the UV filter...

 

In the ExpoDisc manual is mentioned that "some users experienced inconsistend results when using the ExpoDisc with a UV/IR 'cut' filter" and this seems to be my case (although it's only a UV filter, no "cut filter"). I was hoping someone had experienced similar problems, and maybe had a solution... other than fixing the WB manual in LR

[SJP]

1) AWB without UV filter, shot taken without UV filter

2) AWB with UV filter, shot taken with UV filter

3) Manual WB without UV filter, shot taken without UV filter

4) Manual WB with UV filter, shot taken with UV filter

5) Manual WB without UV filter, shot taken with UV filter

 

1 and 2 look similar in WB - admittedly too daylight like for an interior shot but that is the way AWB works.

3, 4 and 5 can be explained by the following:

Using the ExpoDisk with UV/IR turns out slightly 'greener' because the the measured WB also contain a retroreflected contribution from the slightly red filter. So the cases that you manual WB with the expodisk but without the UV/IR give the most neutral results (3&5). No 4 has the greenish tinge as anticipated.

The effect may depend on the way the light strikes the expodisk but in any case all the RAW files should look the same - so copying the WB settings should yield the same results for all the files.(possibly with 1 & 3 slightly green compared to 2, 4 and 5).

 

Anyway what is wrong with taking a picture of the ExpoDisk at a distance and use that to adjust the WB (from Raw)?

 

Or is it that you want to go straight to jpg? If so then remove the UV/IR to WB with the ExpoDisk.

[DrTebi]

Anyway what is wrong with taking a picture of the ExpoDisk at a distance and use that to adjust the WB (from Raw)?

I am sorry, but I don't exactly understand what you mean

 

Or is it that you want to go straight to jpg? If so then remove the UV/IR to WB with the ExpoDisk.

While this is of course possible, it takes time. I prefer not having to remove the UV filter every time I need to set the WB manually. I was hoping that this was not necessary.

[SJP]

I am sorry, but I don't exactly understand what you mean

 

While this is of course possible, it takes time. I prefer not having to remove the UV filter every time I need to set the WB manually. I was hoping that this was not necessary.

 

If you put the expodisk somewhere in the picture (at some distance from the lens) then you can use it later during processing to do a 'spot' WB measurement, using the WB 'dropper' in C1 LE. The WB of that shot is then calibrated and can be used as a reference for all the other shots taken in the same room or under the same lighting conditions. Just select all the other pictures taken under the same lighting conditions and copy the WB setting from the reference shot (using the 'multiple frame' icon in C1 LE).

 

I find that in a large number cases there is a shot with a piece of paper or something else white in one of the pictures - you can use that instead of an ExpoDisk.

 

Using either of these techniques you do not need to remove the filter for getting a good WB.

[DrTebi]

If you put the expodisk somewhere in the picture (at some distance from the lens) then you can use it later during processing to do a 'spot' WB measurement, using the WB 'dropper' in C1 LE. The WB of that shot is then calibrated and can be used as a reference for all the other shots taken in the same room or under the same lighting conditions. Just select all the other pictures taken under the same lighting conditions and copy the WB setting from the reference shot (using the 'multiple frame' icon in C1 LE).

 

I find that in a large number cases there is a shot with a piece of paper or something else white in one of the pictures - you can use that instead of an ExpoDisk.

 

Using either of these techniques you do not need to remove the filter for getting a good WB.

 

Your approach sounds very much like using a grey card. But I think the ExpoDisc is meant to be used differently. You are supposed to hold the disc right in front of the lens and aim at the light source (not the subject) from the subject's point of view.

Before I read the manual... I tried the ExpoDisc by just holding it in front of the lens and pointing at the subject--this does not work. At least not for indoor shots.

 

I haven't tried putting the ExpoDisc into the scene for a shot, and setting the WB manually later on in the software. It's worth a try, but as I said, I don't think that's what the ExpoDisc is meant to be used for.

[Jamie Roberts]

I am using a brand new the Leica 28mm Elmarit ASPH. So yes, it does have the coding, and the setting on the camera is set to "Lens Detection: On + UV / IR"

 

Does this have something to do with it? Should I have this off when doing manual WB shots with the UV filter off? I am a bit confused about this setting.

 

Ok, here's the problem right here, and I'm sorry I didn't catch this before....

 

You're only using a UV filter right? I just assumed you'd be using UV/IR like everyone else with an M8 Sorry.

 

Go back into the firmware and turn the lens detection on (it's coded, after all) but the UV/IR to OFF, since you're not using an IR cut filter.

 

There is no setting in firmware for a UV filter, just for the UV/IR cut filter.

 

If you do this, you will get essentially the same results as you get by taking the filter off. Try it and see, and let us know.

 

You're also completely correct about shooting at the light source through the ExpoDisc. It's not to be used as a grey card.

[DrTebi]

Ok, here's the problem right here, and I'm sorry I didn't catch this before....

 

You're only using a UV filter right? I just assumed you'd be using UV/IR like everyone else with an M8 Sorry.

 

Go back into the firmware and turn the lens detection on (it's coded, after all) but the UV/IR to OFF, since you're not using an IR cut filter.

 

There is no setting in firmware for a UV filter, just for the UV/IR cut filter.

 

If you do this, you will get essentially the same results as you get by taking the filter off. Try it and see, and let us know.

 

You're also completely correct about shooting at the light source through the ExpoDisc. It's not to be used as a grey card.

 

OK, I have made some test shots again, this time with the "Lens Detection" set to "ON", and not "ON UV/IR Cut". The results were surprising... when I first did some random tests, the results were similar to the ones I first posted. But I realized that my light source in the kitchen is kind of odd, especially because the walls are all painted in some greenish white. So I decided to setup my little amateur studio and used one good and strong light source, and also a white fill card. I added a third shot with a grey card as manual WB as well. This is the order of shots taken:

1 - Auto WB, no UV filter

2 - Manual WB with grey card, no UV filter

3 - Manual WB with ExpoDisc, no UV filter

4 - Auto WB, UV filter

5 - Manual WB with grey card, UV filter

6 - Manual WB with ExpoDisc, UV filter

 

The ExpoDisc WB was taken from the subjects point of view, towards the light source.

 

In order to compare the shots better, I setup a little web page where the images can be swapped instead of seeing them below one another:

ExpoDisc White Balance Test

 

If you look in the left bottom corner, you can see that I put a black scarf there that obviously creates problems when shooting with no UV filter. Actually, I think the scarf messes up all the non-UV filter shots.

Now the best one seems to be the grey-card WB and ExpoDisc WB with UV filter... which is the expected results.

 

However--I don't think it's due to the different setting of the "Lens Detection." I did a few random shots with those settings swapped, and could really not notice any difference

 

White Balance is a tough one... for my amateur studio setup I can make it work, but I wonder how I will do it in the future when there is no time to do many test shots and compare...

 

Let me know what you think. Here I am posting only the best result (no need to upload 5 more images), which is the Greycard WB with UV filter. Check out the others at

ExpoDisc White Balance Test

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[Jamie Roberts]

{Snipped}White Balance is a tough one... for my amateur studio setup I can make it work, but I wonder how I will do it in the future when there is no time to do many test shots and compare...

{snipped}

 

White balance is only tough because you're expecting too much from it. I would say "don't worry that much" about it.

 

There are other factors at work in colour reproduction other than white balance, not the least of which is your downstream colour management, your printing output, your display and so on.

 

So I think any of these "white balances" are in the ballpark. None of those objects are controlled either

 

Ultimately, unless you ship stuff to a lab for more correction and processing, you get to decide what the rendition / colour tonality of your photography really is. There are some guides in terms of pleasing skin tones, etc... but the rest is an interpretation.

 

White balance is only a starting point. Many of us only guesstimate it when shooting and then tweak it in post. You're shooting raw, so you should think about that...

 

Even in a RAW workflow, the grey card and the expodisc are useful in difficult light, or when you want a sequence with the same base, or when you have no clue about what the temperature should be (and we're all there at some point), but otherwise their inherent worth is over-rated a lot of the time.

[delander †]

Are you sure you are not using a UV/IR filter because that scarf goes a nice black in all your shots using the filter. I did not think a simple UV filter would have that effect?

 

Jeff

[Jamie Roberts]

Great eye, Jeff!

 

I'd bet the good Dr is actually using a UV/IR-cut filter based on that change (which I didn't even notice... sigh).

 

So he should turn the firmware adjustment back to "on"...

 

Which makes the Expodisc shot a wee bit too green (not much though), and that could be due to red reflections from the filter. Or it could be the downstream post processing / colour profile / matrix in the converter being that much "off" for the M8 with a filter and a vignette correction.

[DrTebi]

Great eye, Jeff!

 

I'd bet the good Dr is actually using a UV/IR-cut filter based on that change (which I didn't even notice... sigh).

 

So he should turn the firmware adjustment back to "on"...

 

Which makes the Expodisc shot a wee bit too green (not much though), and that could be due to red reflections from the filter. Or it could be the downstream post processing / colour profile / matrix in the converter being that much "off" for the M8 with a filter and a vignette correction.

 

Yes of course it's an UV/IR-cut filter... shame on me. I should just have looked at the filter itself. I know this is one of the free filter Leica shipped to all it's users, but I didn't know they actually shipped UV/IR-cut filters. Ahhh... I need a big lesson in filters. Really.

 

Nevertheless, I think doing all the shots again with the right settings is not going to do magic. I agree with Jamie that I shouldn't worry about WB too much. Setting the WB with the ExpoDisc or a graycard when possible will be helpful, but in post processing I will probably still tweak it a bit.

 

Thanks for all your input