Red filter w/ pan film effect

[txfred]

Using a red filters with panchromatic b&w film gives a very dark sky and contrasting bright clouds. Does anyone know of a digital camera technique that results in a similar effect?

[Bill44]

Photoshop! Sorry, couldn't resist that.

[Davey]

I'd 2nd bill on that, B&W filter will perform same effect on RGB colour images, can tweak to make it look like you shot monochrome with whatever colour filter(s) you choose.

I guess the result may differ to if you actually used a red filter on your lens and shot in monochrome. Also I'm unsure about comparisson of digital monochrome shooting to film from personal experience that is. I never shot on B&W film nor used monochrome digitally very much. As for the benefit of shooting monochrome in camera to changing regular colour image to b&w later in processing I don't know but would be interested to hear others experience on this.

I guess some cameras might even simulate the filter effect "in camera" since you could choose to make a monochrome image from just the red pixels thus simulating red filter or combo like red and green pixels thereby simulating yellow filter etc. Unsure if any do that or if there is technical reason for not doing so but if not perhaps custom (or even official) firmware could support that in future.

Sorry, quick edit. The suggestion to use a red filter on your digi cam is dependent upon having a lens that will take the red filter you used on film cam. You could always work around with DIY holder job etc, but depending on your camera it might be awkward (for instance if you have a small compact filter attachment will be more awkward, but still possible I guess).

[txfred]

My note was rushed and poorly written. I am very curious about the technical aspects of digital photography. I thought that this question would be a way to better understand the comparative radiation absorption characteristics of b&w film and the digital camera image sensor.

It is only natural that one should wish to apply prior study and experience to new technologies and applications. Maybe there is a modern equivalent of the SPSE HANDBOOK of PHOTOGRAPHIC SCIENCE and ENGINEERING that you might suggest.

Thanks

[Dave Humphries]

Hi txfred,

Just from a simplistic point of view (I do those best ), I would imagine you could try: obviously if you stick a dark red filter on, the picture will go red, but if you set the camera to record the image in B&W, I would expect you to get similar-ish results to film. But once you've done it, that one version is all you have. The advantage of the PP route is you can fine tune things to get the effect and gradation you were wanting to create.

I don't know a book rec., but I'm sure someone like Colin will.

Cheers,

[bockey]

My advice is to always capture your photo using full colour and for best results use RAW. Now convert to B&W in Photoshop or other program. You will get the best results this way. To get a red-filter result in Photoshop, <layer/new adjustment layer/channel mixer>. Click the monochrome box. This gives a B&W with default settings of Red=100, green=0, blue=0. For a red filter, move red to 200 and the others to say -50. (the three numbers should add to 100 - if not 100 it may be too dark or too light). You can get the effect of any other filter by adjusting the sliders - set red=150 plus blue=-50 gives effect of a yellow filter; set green=200, red=-50, blue=-50 will give effect of green filter. the 'constant' slider can be used for fine adjustments to density.

[Davey]

be aware if you put a red filter on and set camera to b&w and shoot in raw it will still record colour (atleast on mine), it just maybe associates the b&w with the raw the same way it does wb. However like with white balance it isn't set and no info is discarded so you're best off not using red filter and shooting raw and post processing. Obviously jpeg would require in cam b&w and red filter but raw and pp is better approach (of doing the same thing cam does but with more processing power).

Unless you have monochrome camera (can you get them btw?) you wont gain anything by using red filter on cam because essentally it's already filtered at the point of sensor/pixel filter so there is no benefit of red filter on lens. If you had a monochrome sensor (ie no colour pixel filters, just a grid of unfiltered sensors) then red filter would be only way to do it however, and the resolution would be better (as far as red channel goes) and crisper (albeit hardly noticable I'd imagine) due to no interpolation needed to fill in colour blanks on the array.

On average 12megapix (actual total pixels made up of 1R2G1B) camera only around 3megapix is true red if I'm not mistake (please correct if I am) since the rest of the red is filled in by interpolation of surrounding red values. This means monochromatic cameras would be superior from the point of view of res etc. Only way to get colour out of them would be to use tripod and take image with red / green /blue filters on and combine them as channels in pp. Maybe they exist, I don't know.

[Colin Southern]

Just a little "food for thought" ...

If you put a red filter in an SLR it's going to favour red light, and attenuate blue and green. Do this in a warm light where red channel inputs are much higher anyway - say towards the end of the day - and you risk blowing the red channel whilst the green and blue channels are at relatively low lwvels.

[Dave Humphries]

Thanks Davey and Colin,

That's two more reasons not to do it with a lens filter and setting camera to B&W (in addition to the loss of versatility).

Cheers,

[Henry Peach]

Using the channel mixer to convert color photos to BW is the typical way digital photographers get the effects of colored BW filters. You would have to experiment to see what mix of RGB channels gets you the filter you are looking for. For instance 100 Red/0 green/0 blue is going to simulate a much deeper red filter than the Wratten #25 red filter that is commonly used.

[Davey]

as far as photoshop goes many versions have a mixer aimed at b&w conversion. It's under image tab and called b&w (I know that sounds obvious but thought I'd mention it's NOT under filters).

It's basically the same as extended channel mixing coupled with greyscale conversion in that you can alter the levels of various colour channels (including composite colours like yellow) ie. 6 colours over 3 primary. Workflow wise I'd go with this as it's easier but achieves the same thing. Also as henry said you can vary exactly how red the red filter is etc.

The added benefit of this as well as refined workflow (but same effect) is you can see the effect of the colour tweaks on the b&w image immediately (naturally assuming you have preview ticked) and more flexibility than the 3 channel mixer (although you can get the extended channel mixer still the greyscale is extra step). If it saves time and makes life easier without afecting result quality then I'm in!

I don't like cutting corners but I do like real shortcuts People ask do I use a desktop compositor because I like the fancy effects, no it's because I'm lazy! If there is an easy way to do it as good or better I'll do it, to hell with the purists I don't care if it's cheating hehehe. Keyboard shortcuts/ bindings and mouse gestures exist purely to satify those like me (what!!! type 8 words when i can press 2 keys with one hand! I don't think so!!)