pop Posted March 24, 2015 Share #61 Posted March 24, 2015 Advertisement (gone after registration) I am not even remotely talking about filtering light forming an image. Yes, I noticed. However, there might still be others in this thread who also would like to discuss what's written in the thread's title. Link to post Share on other sites More sharing options...
Advertisement Posted March 24, 2015 Posted March 24, 2015 Hi pop, Take a look here Yellow Filter On An M9, Good Idea?. I'm sure you'll find what you were looking for!
jaapv Posted March 24, 2015 Share #62 Posted March 24, 2015 Yes, Alan, but what I am trying to explain is that the colours you are manipulating can only be expressed and measured by the RGB values which automatically translate into the colour channels. You cannot change a colour without shifting the RGB values. In RGB that will affect luminosity as well, btw. I am using a red filter as an example to explain the conceptual difference between working on color channels and working on individual colors. The concept applies to any filter or method. Besides, when I shot b/w I used red filters very frequently for dramatic skies. And then I probably still burned in some on the prints. There is a huge difference between simply playing around with filters and color curves and actually using sophisticated software tools to modify individual colors before grayscale conversion. You and some others don't seem to get this or care, but that's the fact jack. I am hardly the first person to realize this and utilize these tools for great effect. Countless people have been working this way for quite a while. When one shoots color objects to reproduce in b/w there are numerous reasons one might wish to change the tone of individual colors or objects in order to make them stand out or recede. What all of your samples having to do with de-mosaic methods, etc. has to do with the topic is beyond me. It doesn't sound easy, intuitive or very useful and I doubt if that is what the OP is how the OP wants to work. Lenshacker, I sort of feel these responses from you get pretty sidetracked in technical departures that interest you, so I really was addressing Jaapv's comment and trying to explain there is a lot more to color adjusting and b/w conversion than what can be done with changing curves in color channels or using filters in front of the lens. If you and others can't see the benefit of isolating just the blue sky in a scene to darken it before conversion, without affecting the relationship of colors in other parts of the photo, then I question how you look at photography. Consider it sort of like a very accurate graduated filter used just on the sky. Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #63 Posted March 25, 2015 The O56 filter works well enough, the Blue channel response is about 1/4th~1/5th that of the green and red. With the dynamic range of the M8, easily compensated for. I multiplied the Blue channel x4 before doing the interpolation. Quick and dirty FORTRAN code, M1015755 by fiftyonepointsix, on Flickr Done between posts, and it was after Sunset. You get enough spatial contributions from all of the channels even with the O56. This is basically turning the M8 into an M8m. I'm thinking a good way to do this is look at the spectral response of the sensor convolved with the various color filters and use a set of "spectral gain flattening coefficients" in the code for each filter. That would make it behave very closely to the M Monochrom. I can compare the two. Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #64 Posted March 25, 2015 I can't figure out why you'd filter out the blue then boost the blue channel. But I guess you haveva reason for going through all that trouble. Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #65 Posted March 25, 2015 Yes, Alan, but what I am trying to explain is that the colours you are manipulating can only be expressed and measured by the RGB values which automatically translate into the colour channels.You cannot change a colour without shifting the RGB values. In RGB that will affect luminosity as well, btw. Yes I think we all know that the data is stored in three color channels. But a filter broadly changes the entire color curve of a channel. So manipulating colors that way is very limited and crude. Wheras in post, I can make a single pixel any value I like. BTW I don't have to limit myself to RGB channels. I could work on HSL or CMYK if I prefer. Link to post Share on other sites More sharing options...
jaapv Posted March 25, 2015 Share #66 Posted March 25, 2015 Yes. separating the colour from the luminosity is often a good idea. Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #67 Posted March 25, 2015 Advertisement (gone after registration) I can't figure out why you'd filter out the blue then boost the blue channel. But I guess you haveva reason for going through all that trouble. With the orange filter over the lens: Blue is no longer "blue". Green is no longer "green", they are measuring light above 560nm. The Blue channel is sensitive all the way into RED. It's less sensitive into red, so it needs to be boosted to equalize. By picking the right factors to equalize the channels, all of this can be done in a batch process: pick the filter in use, output a linear monochrome file. Same applies to the M9, will try that later. Sub-IFD field, new since I worked with this stuff in the 90s. I wrote a "smart-HEX" editor that allows you to add subroutines to process the data as you dump it. After you have the routines, make them into a stand-alone program. Figured out the Kodak DCS200 using the same program. It is old, and runs on DOS. So by using the Orange filter over the lens, you turn all of the channels into one big monochrome sensor. Which is what the OP wanted to do. Link to post Share on other sites More sharing options...
jaapv Posted March 25, 2015 Share #68 Posted March 25, 2015 Righ.t One could even use Photoshop Greyscale ( the standard setting for Monochrom files) Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #69 Posted March 25, 2015 I will look more closely at the Monochrom .DNG and borrow from it. There are all sorts of interesting fields stored in the DNG file that you normally never see. Link to post Share on other sites More sharing options...
jaapv Posted March 25, 2015 Share #70 Posted March 25, 2015 Indeed, it is a DNG variant that could not even be read by most applications and OS-X initially. It would be interesting to get the M8 closer to the Monochrom. Yu will not be able to match it, though, because the aberrations induced by the Bayer filter will remain, and the light/DR loss of that same filter will remain as well. OTOH you might run into some interesting aspects that could affect the Monochrom too. Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #71 Posted March 25, 2015 Yu will not be able to match it, though, because the aberrations induced by the Bayer filter will remain, and the light/DR loss of that same filter will remain as well.. The Monochrom will of course produce the highest-fidelity possible. And I can just here my wife, "Why did you spend $8000 when you could have just used the code that you wrote for me!" Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #72 Posted March 25, 2015 So by using the Orange filter over the lens, you turn all of the channels into one big monochrome sensor. Which is what the OP wanted to do. No, the OP asked if using a yellow filter is a good idea. You've shown how to jump through hoops for some reason. I've suggested he see what he can do with conversion software and demonstrated why to use it. The orange filter doesn't reduce its complementary color? How does it avoid that? This is an artistic process so I've asked you and anyone else interested to shoot an example of a typical scene through a yellow filter as the op asked, or even any moderate or deeply colored filter along with the same shot made without a filter. Then do your grayscale conversion and make these files available to us. Why haven't you provided the material to demonstrate your opinions? I did this very test with 3 filters and have determined using the simple quick and easy color sliders in C1 is a better way to go. Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #73 Posted March 25, 2015 I posted results with the Yellow filter and answered the original question, then you brought up the RED filter example. The O56 gives amazingly good results. I will test the R60. If you really want me to upload the FORTRAN source code, I will. No hoops involved, writing software is just typing and required much less typing than this thread Using the color filters with the M8 and M9 for the purpose of doing a conversion to monochrome is a good idea . Original question answered. Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #74 Posted March 25, 2015 I posted results with the Yellow filter and answered the original question, then you brought up the RED filter example. The O56 gives amazingly good results. I will test the R60. If you really want me to upload the FORTRAN source code, I will. No hoops involved, writing software is just typing and required much less typing than this thread Using the color filters with the M8 and M9 for the purpose of doing a conversion to monochrome is a good idea . Original question answered. OK I'd like to study those amazing results. So will you post to Dropbox or some other place the full res tif and the raw of the same image shot without a filter? Somehow it makes sense to you, but not to me, to use a filter in order to reduce the color to one or more channels and then write code to boost the underexposed image in order to get some of this information back to a "normal" exposure level. Have you ever tried the color to b/w system in C1? Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #75 Posted March 25, 2015 Once I have the custom software more stable, I will do a comparison between the Monochrom and using color filters on the M8/M9. Yesterday is the first day that I was able to output a DNG file from my software, and I am still debugging it. I find this interesting. The person that described the Demosaic process to me over the phone worked with Bryce Bayer, that was when the DCS200 was new. Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #76 Posted March 25, 2015 Once I have the custom software more stable, I will do a comparison between the Monochrom and using color filters on the M8/M9. Yesterday is the first day that I was able to output a DNG file from my software, and I am still debugging it. I find this interesting. The person that described the Demosaic process to me over the phone worked with Bryce Bayer, that was when the DCS200 was new. So let me understand this. The monochrome will be used with no filter. But with an M9, you plan to shoot through an orange filter (at the same exposure or do you have to compensate a stop or two?) record the images through the sensor's three separation filters, and then you believe you have developed software that can boost the signal with from those underexposed images to be equal or better than what was made with no filter? And the point of all of this for regular photographers? You still haven't answered my question about C-1... have you used it and the color sliders for b/w conversions? Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #77 Posted March 25, 2015 I plan to use the Monochrom and the M8 (or M9) with the same color filter, then run my software for the conversion. If the conversion process looks good, then another person can incorporate it into an application package. If no one wants to do that, I most likely will. I like to code an algorithm in FORTRAN, then convert to C. I don't use C1. I keep my post-processing to a minimum. I have spent most of my life working with computers, started with digital imaging in 1979. I've written more image processing software than most people, but for myself- prefer doing as much in-camera as possible. Being able to use a color-filter with a color camera and then batch-process it into linear-monochrome DNG is interesting, I do not know any other software designed to do that. If anyone knows of conversion software specifically designed to be used with color filters on the lens, would be interesting to hear about it. Link to post Share on other sites More sharing options...
AlanG Posted March 25, 2015 Share #78 Posted March 25, 2015 Here are some examples of what is possible using only the color sliders to b-w in C-1. This is from the jpeg of a cheap p&s. I pushed a few examples to the extreme to illustrate the range available. The first one is with the sliders in a neutral position and show how without any adjustment, the red shorts and cyan shirt have about the same grey value. 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/242054-yellow-filter-on-an-m9-good-idea/?do=findComment&comment=2787010'>More sharing options...
jaapv Posted March 25, 2015 Share #79 Posted March 25, 2015 Actually, nobody ever doubted the effectiveness of colour manipulation at B&W conversion.... Link to post Share on other sites More sharing options...
Lenshacker Posted March 25, 2015 Share #80 Posted March 25, 2015 This is a 100% crop of the converted image, Orange filter. You can see the artifacts of the Bayer filter on the stem of the leaf. M1015771_crop by fiftyonepointsix, on Flickr No sharpening "at all". Will add some to the routine. This is the full image scaled down, M1015771_s by fiftyonepointsix, on Flickr Taken on a different day, better lighting- but same lens and filter on the Monochrom. L1001608_crop_Monochrom by fiftyonepointsix, on Flickr You can see some artifacts, it is digital. Totally worth the $8000 that I spent on it. Link to post Share on other sites More sharing options...
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