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Yellow Filter On An M9, Good Idea?


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Yes, it is a good idea if you are sure you are going to use it for B&W.

Simulating colour filters in postprocessing is fine, but amplifying one colour channel over the other two will increase noise.

Better to do so when the camera adjusts exposure to compensate for the unbalanced light.

Edited by jaapv
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Yes, it is a good idea if you are sure you are going to use it for B&W.

 

 

Oh yes, I should have added that I convert to B&W 99.9% of the time.

 

Of course the simpler solution would be to stick a Monochrom on the end of my lens, but it took me 5 years to get an M9, so probably another couple of years yet.

 

Thanks for the link Jeff.

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Looking at the spectral response of the Sensor: Yes, you will get better color separation using the Yellow filter. The Green channel is sensitive farther into the Blue region than a standard color separation filter. Using the Yellow filter will cut the green channel response that extends into the blue/green region. Overall, the Bayer filter cuts 1 Stop of light, not 2 stops as would be the case in true color separation filters.

 

And another experiment to run to compare the M9 and Monochrom, Yellow and Orange filters over each.

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It's the same for colour photos. If you are shooting under 2500°K lighting, a blue 80b colour filter goes part way to colour balancing the result, so when you process the file, the red component is reduced and you don't have to boost the blue channel as much. The result - less noise. Of course, you have to boost exposure, but the added noise from that is somewhat less than the benefit of not boosting the blue channel as much.

 

However, the convenience of being able to shoot without filters vs. small gains in noise has generally put filters out of business, but if you still have some…

 

Henning

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All any filter does is reduce the amount of light passing through it. A yellow filter cuts out blue but also cuts all light somewhat as it is not pure. Since the digital camera already makes separation images, you can adjust the color in these files any way you like before doing b/w conversions.

 

All you accomplish by shooting through a yellow filter is to destroy the separation images and restrict your ability to adust the image. B/w images on film or the MM made with a yellow filter are way more constrained than what can be done from a color image before b/w conversion. E.g. working from a color file, you can lighten or darken blue and yellow objects independently in the same photo.

Edited by AlanG
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Hi all,

 

I know that yellow filters on a Monochrom is just as worthwile as on a film camera, but how about on an M9?

 

Is there any benefit or point to it, or is it best to just add the effect in post?

 

Anyone else tried colored filters on M8/M9 etc?

 

This is one of those questions that is easy to answer with a test. Try with/without the yellow filter and then decide which results you prefer. There are pro's and con's of each method, the deciding factor should be which gives the results that you prefer.

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All any filter does is reduce the amount of light passing through it. A yellow filter cuts out blue but also cuts all light somewhat as it is not pure. Since the digital camera already makes separation images, you can adjust the color in these files any way you like before doing b/w conversions.

 

All you accomplish by shooting through a yellow filter is to destroy the separation images and restrict your ability to adust the image. B/w images on film or the MM made with a yellow filter are way more constrained than what can be done from a color image before b/w conversion. E.g. working from a color file, you can lighten or darken blue and yellow objects independently in the same photo.

This is based on the assumption that shifting the values in the colour channels does not degrade the image, Alan. That is not true, it will increase noise. It is better, imo, to have the camera increase exposure according to the light passing through a filter.

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If you are using a yellow filter are you not trying to make blue things darker? The necessity to increase exposure is only to compensate for the filter factor. Making things darker will not add noise. And making specific colors lighter... which shooting through a filter cannot do, the noise is minimal in my experience.

Edited by AlanG
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And the filter factor is due to a part of the spectrum being kept back, which the camera exposure meter will correct for, giving you an optimally exposed, albeit colour-skewed image..

In Photoshop you will be manipulating the values in the colour channels, which will inevitably increase noise..

Edited by jaapv
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So you are saying that the red and green filters in the sensor are not adequate for blocking out enough of the blue light. So the blue light must be reduced somewhat before it hits the separation filters. What would be a case where this is needed?

 

With b/w film an increase in exposure will give more density. But with digital an increase past a certain point will just clip highlights. That is one advantage that negative film still has over digital.

Edited by AlanG
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Any case where you would want to use a yellow filter (or any other colour filter for that matter) on a black-and-white image.

 

Confession -I seldom took my own advice. Situations where one would use a yellow filter are usually low-ISO where noise is not much of a problem. And if one forgets to remove the filter for a colour shot one is in a bit of trouble. It is not a simple colour balance adjustment - try it and the reds and greens are shot.

 

However, it is hard to think of any harm being done to the B&W image, so it can only help.

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So you are saying that the red and green filters in the sensor are not adequate for blocking out enough of the blue light. So the blue light must be reduced somewhat before it hits the separation filters. What would be a case where this is needed?

.

 

Page 14 of the spec sheet.

 

http://www.onsemi.com/pub_link/Collateral/KAF-18500-D.PDF

 

Spectral response of the CCD used in the M9. A Y48 would cut out much more Blue and Green than the Dye used in the Bayer filter. Again- would be an interesting experiment.

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Page 14 of the spec sheet.

 

http://www.onsemi.com/pub_link/Collateral/KAF-18500-D.PDF

 

Spectral response of the CCD used in the M9. A Y48 would cut out much more Blue and Green than the Dye used in the Bayer filter. Again- would be an interesting experiment.

 

So you just want to make a b/w image that represents the red light? Why?

 

Again, as a photographer, I suggest people stop looking a this as an engineering experiment and more at how one can best use their tools in a creative way.

 

I've posted these before. Notice how the sodium vapor lighting affects the colors in the dusk shot.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Edited by AlanG
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That would require an R60 filter. The Y48 cuts about half-way into the response of the green pixels.

 

Yes I know. But why? In post, you can just darken all of the colors except red if you like. Or make any color pretty much any shade of gray you want. As in my examples above, you can adjust a color file to your heart's content to get any kind of b/w rendering you want... and this is independent of whether the separation filters could cut out the color completely. There is an example where both the blue sky and red are lightened. Another where red is darkened and yellow, magenta and blue are lightened. I can't see any practical reason to need to cut out the colors more completely than can be done with the camera's built in filters and good software unless there was some kind of scientific project involved.

 

What are you or others as photographers trying to accomplish that can only be done by using a filter?

 

Regarding noise, that only may increase (generally very slightly) if you lighten a color significantly. But using a filter in front of a lens can only darken colors. And darkening a color in post will not add noise. Compensating exposure for the filter in front of the lens (filter factor) won't make the non-filtered colors lighter as those have to be exposed correctly to not clip the highlights. But of course red lipstick on lips will look lighter in the red channel than the lips will look in just the green or blue channels.

Edited by AlanG
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