White balance settings when using ND filters

[Guest]

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I’ve noticed that when using a 10 stop BW filter on my Noctilux 095 the picture is considerably warmer than without the filter both shot at auto WB. Not sure if the problem is with the Auto who’re balance or a crappy filfer 

neil

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[lykaman]

13 minutes ago, NW67 said:

I’ve noticed that when using a 10 stop BW filter on my Noctilux 095 the picture is considerably warmer than without the filter both shot at auto WB. Not sure if the problem is with the Auto who’re balance or a crappy filfer 

neil

I thought you had put your cameras away' and had dedicated time for the family ... L

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[Guest]

Camera is in the hotel. Just something I noticed while I was away and wanted to ask the Gang

neil

16 minutes ago, lykaman said:

I thought you had put your cameras away' and had dedicated time for the family ... L

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[andybarton]

If it’s a good quality filter, it should be completely neutral in colour. That’s why it’s called a Neutral Density filter. 

 

If it’s a cheap one, you’re on your own. 

[Richardgb]

I don't have the M instruction book to hand but AFAIK, the white balance on an M is not measured via the lens but elsewhere (can anybody confirm?) thus would not be affected by an off-colour ND filter.

As for the difference in colour, if the subject contains a truly neutral grey area, e.g. a test card, then anything off-colour should be easily corrected in post-production for example using the 'grey dropper' near the white balance scale in Lightroom.

[Guest]

50 minutes ago, andybarton said:

If it’s a good quality filter, it should be completely neutral in colour. That’s why it’s called a Neutral Density filter. 

 

If it’s a cheap one, you’re on your own. 

B£W are not what I would call cheep but then I wouldn’t know would i

neil

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Example with filter

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Without

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[kinch123]

Why don't you just slap an Expodisc over your lens with ND Filter and take a test pic to tweak WB in LR later? Or Similarly take a test pic with WB card in the frame? Sorted (maybe).

As for WHY it happens, that's beyond my pay grade. I'd have to guess that the 'Neutral' in ND is something the manufacturer strives for rather than an absolute fact. In other words, it's not going to attenuate all wavelengths exactly the same. Start collecting photons in silicon buckets over multiple seconds exposures and convolve a bunch of what-ifs about response curve of your ND filter and sensor noise and adjacent bucket crosstalk interactions x elapsed time with black box DNG cooking algorithm and who knows? I'm just talking out my posterior here in the hope that someone reading who does have a deep understanding of the technical stuff will have a go.

But in the mean time, why not just try Para 1 and see if the results are to taste?

Edited August 23, 2019 by kinch123

[kinch123]

Also, I guess that Automatic White Balance Algorithm starting point is looking at the histograms of the three Bayer Channels. When you take an elapsed exposure, you're collecting more area of 'white' = closer to maxed out RGB image data, are you not? That's what I see when I look at the smoothed/smeared out water in the elapsed exposure. This in itself, should result in the AWB algo giving a different estimation of 'true' white point. There isn't a little goblin living inside your camera that recognises that you are using an ND filter and taking a photo of water running over rocks. A bit like taking a photo of a black cat in front of a pile of coal using a very traditional spot or centre-weighted meter. User has to deal with meter's very primitive assumptions about what the scene is made up of.

[Michael Geschlecht]

Hello Neil,

Nice photos.

The 2 are certainly different.

Is it possible that there is something on the filter that should not be there?

On 1 surface of the filter or the other?

With a a dark filter it is sometimes difficult to tell if there is something on it that should not be there.

Also: How much of the entire photo are we looking at?

Best Regards,

Michael

Edited August 23, 2019 by Michael Geschlecht

[kinch123]

Totally OT, but can any civil engineer explain how that steel bridge reinforcement hack is working? Guess it's not there to help with arch load bearing... Is it to reinforce the stone coursework against buckling outward as heavier modern loads compress the rubble packing?

[Guest]

3 hours ago, Michael Geschlecht said:

Hello Neil,

Nice photos.

The 2 are certainly different.

Is it possible that there is something on the filter that should not be there?

On 1 surface of the filter or the other?

With a a dark filter it is sometimes difficult to tell if there is something on it that should not be there.

Also: How much of the entire photo are we looking at?

Best Regards,

Michael

Michael

Your looking at the whole picture.....it’s not cropped

ivevhad this filter for over 5 years so maybe that has something to do with it. 

Neil

Edited August 23, 2019 by Guest

[jaapv]

AWB is a complicated algorithm, and it is hard to tell why it differs from shot to shot. If you really want to know whether the filter makes a difference, set your camera to "daylight" and do the experiment.

[Maarten]

Neutral gray is very difficult to achieve, perhaps even more so in glass because of the high processing temperature when the filter is made.
The dyes used to make the glass gray need to to pass the processing step, limiting the choice of dyes.

Normally this is not a problem, most pictures are taken with camera's reading the WB from the sensor.
The Leica M measures the WB via the small eye in front of the flash shoe. The camera is not aware that a filter is on.
In the exif you will probably find the same WB-setting of the camera in both pictures.

The solution is given already above: use the manual WB setting with a gray card or even a white piece of paper.

[jaapv]

Are you sure? AFAIK that window is a light meter to determine the f-stop and to control the M-TTL system. The Digilux2 had an external WB window and that one had two sensors.

Easily tested: screw a yellow filter on and see if the AWB attempts to correct. (it won't succeed completely, though) next cover the window and look for the differences.

[Guest]

I can easily fix it but wondered why it did it on my M10. On my Hasselblad H6D100c I don’t have this issue perhaps it’s to do with the quality of the manufacturing........ I don’t know

neil 

[Gelatino]

Have a try there:

https://breakthrough.photography

1.  
2.  

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Hallo,

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[Guest]

36 minutes ago, Gelatino said:

Have a try there:

https://breakthrough.photography

1.  
2.  

I’m really not into buying more filters. I can easily correct it I just wondered why it was doing it as my H6D doesn’t do it and I use BW filters on that two

[Jeff S]

5 hours ago, jaapv said:

AWB is a complicated algorithm, and it is hard to tell why it differs from shot to shot. If you really want to know whether the filter makes a difference, set your camera to "daylight" and do the experiment.

+1. Or any other fixed K setting.  

Jeff