250swb Posted March 30, 2012 Share #41 Posted March 30, 2012 Advertisement (gone after registration) "Coloured filters can produce great effects for black and white photograph. By using coloured filters – typically yellow, orange, red and green - You can lighten or darken the tone of coloured subjects and also effect contrast dramatically. Black & white images can sometimes lack impact because colours that are well differentiated in nature – can be equivalently luminous in shades of grey. A coloured filter can lighten the tone of the one colour, while darkening the tone of a complementary colour. For Example yellow and yellow/green filters can bring more brilliance to landscape photographs and create better differentiation of green tones in vegetation. Yellow and orange filters can enhance clouds on a blue sky and red filters can even raise them to dramatic thunderstorm strength. B+W TIP: A very simple rule can be used to determine which filter should be used: To lighten a subject colour, use a filter of the same colour. To darken a subject use a filter of a complementary colour" Source B+W. Alan, yes if you half paint a white wall green and use a green filter the green part will look lighter than the normal un-filtered tone rendered on a B&W neg. If on the other hand you also added a red section to the wall that would look darker than a normal rendered tone when using a green filter. I don't know why you need a white wall to paint green and red on though. Steve Link to post Share on other sites More sharing options...
Advertisement Posted March 30, 2012 Posted March 30, 2012 Hi 250swb, Take a look here Using Yellow Filter. I'm sure you'll find what you were looking for!
AlanG Posted March 30, 2012 Share #42 Posted March 30, 2012 Alan, yes if you half paint a white wall green and use a green filter the green part will look lighter than the normal un-filtered tone rendered on a B&W neg. Would you bet your house on this? Link to post Share on other sites More sharing options...
pico Posted March 30, 2012 Share #43 Posted March 30, 2012 Gentlemen, perhaps we have a cultural or language issue. It appears that you all know very well how to use color-contrast (B&W) filters. I see arguments pivoting about the expression (paraphrased) "a filter lightens tones of the same hue", which is true and can be expressed as "a filter darkens tones complimentary to the hue of the filter" and we know that an increase of exposure is required. And of course we mean lighten, darken as in the print. I see B&W photography as making color pictures without hue. Puzzle that one out! Good discussion, regardless. Link to post Share on other sites More sharing options...
StS Posted March 30, 2012 Share #44 Posted March 30, 2012 Yes, the difference appears to be purely linguistic, one side talking about the mechanism, the other about the result. For our scientific discussion, I took this picture out of the B+W catalogue. If we pick, for example, the green filter 061, it will have its maximum transmission of 90% in the 520 nm (green) range*. Which means, that even for green light, 10% of the light is lost due to the green-filter. As we all know, we increase the exposure in the next step. Let's assume, we double the exposure. Now, the exposure from blue light (around 450 nm) will increase from 12% to 24%, compared to an unfiltered exposure, but the exposure of green 520 nm light will increase from 90% to 180% of the unfiltered exposure. Red having 650 nm will increase from 48% to 96% of the unfiltered exposure. So we have, as a result of the filter and the increased exposure still a strong attenuation of the exposure of blue light, a strong increase of the exposure of green light and about the same exposure for red light. So the filter always attenuates. But in combination with the increased exposure, green gets more exposure compared to higher or lower wavelenghts. Hope this helps Stefan *I'm ignoring infrared above 700 nm 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! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/175672-using-yellow-filter/?do=findComment&comment=1968627'>More sharing options...
StS Posted March 30, 2012 Share #45 Posted March 30, 2012 ...as a side note, this also explains, why red filters need so much extra exposure - filter 091 cuts out almost the whole visible spectrum, which is roughly between 420 nm and 650 nm. Link to post Share on other sites More sharing options...
AlanG Posted March 30, 2012 Share #46 Posted March 30, 2012 Yes, the difference appears to be purely linguistic, one side talking about the mechanism, the other about the result. He got the result right but the process backwards. That is pretty much what I said in the beginning. I went back and re-read his and my posts and I don't think it has anything to do with linguistics. I certainly am past trying to explain it any other way. If anyone wants to think that a filter increases brightness, that is fine with me. I'm sorry I wasted my time. Well I've gotten rid of most of my filters, but still have a few lying around. 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! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/175672-using-yellow-filter/?do=findComment&comment=1968641'>More sharing options...
250swb Posted March 31, 2012 Share #47 Posted March 31, 2012 Advertisement (gone after registration) It is easy to test. Find a colour image to represent a B&W print with some grass or anything else green and open it in Photoshop. Go to the 'convert to black and white' utility and apply a green filter. The green tones will be lighter than in the default view. Silver Efex is more accurate at this than Photoshop but it is obvious what a green filter does. This is entirely different to your idea that tones are only lightened in the print due to the increase in exposure of the negative, and that is proven wrong. Steve Link to post Share on other sites More sharing options...
stunsworth Posted March 31, 2012 Share #48 Posted March 31, 2012 This is entirely different to your idea that tones are only lightened in the print due to the increase in exposure of the negative, and that is proven wrong But that's just the way that Photoshop works internally to maintain the overall brightness of the scene. In the physical world if you remove the non-yellow elements in a scene by using a yellow filter the scene _has_ to get darker as the filter is removing much of the light. The photographer then has to compensate for this effect by increasing exposure. Link to post Share on other sites More sharing options...
pop Posted March 31, 2012 Share #49 Posted March 31, 2012 May I suggest that one member who happens to own a camera take two pictures of the same scene, one with a filter and one without, turning off all automatic settings? Then,come next christmas when all frames are exposed and developed we can compare the negatives. Link to post Share on other sites More sharing options...
andybarton Posted March 31, 2012 Share #50 Posted March 31, 2012 I could do that for you. I don't see much pointy though, as people have been using coloured filters for decades Link to post Share on other sites More sharing options...
rob139 Posted March 31, 2012 Share #51 Posted March 31, 2012 It is indeed very easy to test. Put a redfilter on your lens, make a picture with the required exposure. Now use that same shuttertime, same subject, but without the redfilter. Put the two pictures next to each other and compare the results. I think you will find that the first picture (with the filter) is much darker than the second one. The conclusion can only be: a filter does not lighten things, it darkens things. And it blocks specific colors extra. The fact that it seems to lighten things is relative, it is the result of two different exposure times. But I agree that the discussion is probably semantic. It's just what you are looking at, the light meter, or the result. Rob Link to post Share on other sites More sharing options...
250swb Posted March 31, 2012 Share #52 Posted March 31, 2012 But that's just the way that Photoshop works internally to maintain the overall brightness of the scene. In the physical world if you remove the non-yellow elements in a scene by using a yellow filter the scene _has_ to get darker as the filter is removing much of the light. The photographer then has to compensate for this effect by increasing exposure. Well yes of course. Lets not get confused, Photoshop is only mimicking what a filter does. So presumably you are still saying that a filter will not have the effect of lightening anything of the same colour when it comes to the print? Steve Link to post Share on other sites More sharing options...
250swb Posted March 31, 2012 Share #53 Posted March 31, 2012 The fact that it seems to lighten things is relative, it is the result of two different exposure times. Rob So you disagree with B+W as well? Extended exposure time is only to account for the strength of the filter. Try denying the example I have given before. Two filters both of the same filter factor, so both require the same exposure time, one is yellow, one is blue. The blue will lighten blue sky in the print because it is filtering out its own colour. The yellow will darken a blue sky because it is filtering out the complimentary colour. That is how it works. Steve Link to post Share on other sites More sharing options...
stunsworth Posted March 31, 2012 Share #54 Posted March 31, 2012 Lets not get confused, Photoshop is only mimicking what a filter does No it isn't. Photoshop is also doing the equivalent of increasing in the exposure. With a camera that increase in exposure is done by the photographer _not_ the filter. Left uncorrected the yellow filter would cause the photographed scene to be darker. Link to post Share on other sites More sharing options...
rob139 Posted March 31, 2012 Share #55 Posted March 31, 2012 So you disagree with B+W as well? Extended exposure time is only to account for the strength of the filter. Try denying the example I have given before. Two filters both of the same filter factor, so both require the same exposure time, one is yellow, one is blue. The blue will lighten blue sky in the print because it is filtering out its own colour. The yellow will darken a blue sky because it is filtering out the complimentary colour. That is how it works. Steve If you want to put it that way, yes I disagree with B&W. I think they simplified their explanation to get the point of how a filter works across. I don't blame them for doing that, because I can understand it. As for your other point, I am not denying the effect of filters, but the effect is relative, compared to for instance the shutter time. Rob Link to post Share on other sites More sharing options...
01af Posted March 31, 2012 Share #56 Posted March 31, 2012 Let's not get confused, Photoshop is only mimicking what a filter does. No, it doesn't. Instead, it is mimicking the usage of a filter—which includes increasing the exposure due to the filter's opacity. That's essential. So presumably you are still saying that a filter will not have the effect of lightening anything of the same colour when it comes to the print? Sure. Because a filter alone does not lighten anything. It will only make things darker, period. For exmaple, a medium yellow filter will darken violet and blue by the equivalent of, say, two f-stops, darken green by about one f-stop, and darken yellow, orange, and red by a small fraction of an f-stop which for practical intents and purposes is mostly negligible. By the way, white will also become darker. Without filter, yellow is a pretty bright colour but white is even brighter. With a yellow filter, yellow will remain what it is and white will become yellow ... so white will get pulled down to yellow level. On the yellow filter's mount there's "2×" engraved—so you will increase exposure by one f-stop when shooting through this filter. As a result, violet and blue will effectively get darkened by one f-stop, green will remain unaltered, and yellow, orange, and red will appear lightened by almost one f-stop. So you disagree with B+W as well? Yes, sure. Because B+W is describing the results of proper usage of the filters, not the isolated effects of the filters' colours alone. Do not confuse B+W's broad description with the topic of this discussion which goes much deeper into the details of how a filter works in black-and-white photography. Link to post Share on other sites More sharing options...
AlanG Posted March 31, 2012 Share #57 Posted March 31, 2012 See, a waste of time. 250swb... you're putting us on, right? It truly is amazing how those little filters generate so much additional light to illuminate entire long distance scenes. BTW, Photoshop and Silver Effects are dealing with color separated images that have already been shot through 3 filters. Link to post Share on other sites More sharing options...
250swb Posted April 1, 2012 Share #58 Posted April 1, 2012 Yes, sure. Because B+W is describing the results of proper usage of the filters, . Exactly, why would anybody want to make it more complicated? This thread didn't start out as a deep in depth question about exactly how filters work. And although our the differences are only semantic they are important. But it evolved into a round the houses discussion because somebody had a small bit of information they wanted to use for the purpose of being pedantic and argumentative, rather than communicative to a wider audience or the novice. It is not constructive or clever to tell people that.... 'You want to lighten green, so first you make everything else darker with a green filter and then compensate for this by increasing the exposure' or 'You want to darken blue, so you have to make everything else lighter with a yellow filter and compensate for this by increasing the exposure' It may be true, but then why would you say it? Unless you wanted to embed a semantic dichotomy into a novices head ? Nobody should need to know how a filter works to if you want to encourage them to use one, just what it does does is enough. B+W and pretty well everybody else on the internet describe it in a simple way because it aids communication. This thread was answering basic questions about filters, not a competition to see who could make it complicated. Steve Link to post Share on other sites More sharing options...
250swb Posted April 1, 2012 Share #59 Posted April 1, 2012 See, a waste of time. 250swb... you're putting us on, right? It truly is amazing how those little filters generate so much additional light to illuminate entire long distance scenes. BTW, Photoshop and Silver Effects are dealing with color separated images that have already been shot through 3 filters. I don't know AlanG, all I see is somebody who needed to publish a photograph of his filter drawer in the same way that Napoleon awarded himself the Legion d'honneur. As if it is a qualification, lol! I'll stick with explaining filters to people the way B+W do it, they have enough scientists and marketing people to realize communication is important rather than pedantism. Steve Link to post Share on other sites More sharing options...
andybarton Posted April 1, 2012 Share #60 Posted April 1, 2012 Someone will recommend putting a yellow filter on a digital camera next... Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.