Using a red filter with colour film

[Paul Manuell]

Would taking such a photo then converting it to b&w give the same or similar result as shooting with b&w film and a red filter?

 

[laser]

The red filter image will yield blue and green items as black and red items as white. Black-and-white film will render blue, green, and red images at different levels of gray proportional to the spectral sensitivity at each wave length.

www.makingKODAKfilm.com

 

[Paul Manuell]

The red filter image will yield blue and green items as black and red items as white. Black-and-white film will render blue, green, and red images at different levels of gray proportional to the spectral sensitivity at each wave length.

www.makingKODAKfilm.com

Sorry, I think you've misunderstood what I'm asking. I already know how different b&w film looks with a red filter compared to without, what I'm asking is if shooting a colour film with a red filter then converting that photo to b&w gives similar results to shooting with a b&w film and red filter in the first place?

 

[AgX]

Would taking such a photo then converting it to b&w give the same or similar result as shooting with b&w film and a red filter?

How do you intend to convert it to b&w ?

,Printing on standard paper, or on panchro-paper or by means of panchro-film interpositive?

Using a red filter will in any case render the sky parts of the colour negative with lesser overall density than without.

 

[Paul Manuell]

How do you intend to convert it to b&w ?

The same way everyone else converts colour photos to b&w

 

[AgX]

I do not understand.

 

[Paul Manuell]

I do not understand.

By getting the negative scanned and then converted on a computer.

 

[AgX]

By getting the negative scanned and then converted on a computer.

You put your question in a 100% analog thread.

 

[Paul Manuell]

Why bother? You can do it in software.

Now I don't understand.
Ok, this is the situation. I don't own a computer, I get all my films developed and scanned for me in my local lab. I then go to the lab when they're ready and go through the scans with the owner on their computer and get him to do any editing I want doing, eg., cropping, lightening or darkening, b&w conversions etc. I know before I even get the films developed that there're going to be some shots I've taken with b&w conversions specifically in mind, and knowing how red filters work on b&w films prompted me to start this thread, to ask if a red filter would be worth using on a colour film where you intend to convert a particular shot to b&w. In a nutshell, would the result be the same as if shot on an actual b&w film and red filter?

 

[kevs]

Hi Paul, you posted your response after I deleted my response, which I had second thoughts about. Sorry about that.

It might work, I don't know. Give it a try.

You didn't say you don't have a computer in your OP. My point about software; most image editors have the ability to split digital images into three layers; Red, Green and Blue. Imagine you could do that with a colour print. The layers can be desaturated (removing colour), blended and worked on in software. Taking the R layer on its own and desaturating it will result in an image similar to one you'd get on B&W film with a red filter. It wouldn't be exactly the same because most red filters also pass some orange and yellow light, plus a tiny bit of green and blue. Blending the R layer with the Y and B layers in certain ways will give a more accurate result; and a different and more controllable one than you'd get by simply desaturating all three layers (R, G and B) together.

So there's no real advantage in using a coloured filter in an ultimately digital setting. You also lose the ability to go back to the full-colour image.

HTH.

 

[Paul Manuell]

You put your question in a 100% analog thread.

Yes, because my Pentax645NII is 100% analogue, as is the film I put in it. Also, I don't own and never have owned a digital camera, so have been working 100% analogue since I started photography in the '80s.

 

[Paul Manuell]

Hi Paul, you posted your response after I deleted my response, which I had second thoughts about. Sorry about that.

It might work, I don't know. Give it a try.

You didn't say you don't have a computer in your OP. My point about software; most image editors have the ability to split digital images into three layers; Red, Green and Blue. Imagine you could do that with a colour print. The layers can be desaturated (removing colour), blended and worked on in software. Taking the R layer on its own and desaturating it will result in an image similar to one you'd get on B&W film with a red filter. It wouldn't be exactly the same because most red filters also pass some orange and yellow light, plus a tiny bit of green and blue. Blending the R layer with the Y and B layers in certain ways will give a more accurate result; and a different and more controllable one than you'd get by simply desaturating all three layers (R, G and B) together.

So there's no real advantage in using a coloured filter in an ultimately digital setting. You also lose the ability to go back to the full-colour image.

HTH.

Sorry, all that has gone totally over my head. I don't own a computer, never have done and wouldn't know how to do any of what you just said even if I did.

 

[kevs]

Sorry, all that has gone totally over my head. I don't own a computer, never have done and wouldn't know how to do any of what you just said even if I did.

I'm sorry about that. You asked a complex question. It's never too late to learn...

 

[David A. Goldfarb]

If you’re sitting with the lab owner at a computer deciding how to print your images, then you’re doing digital image editing, even if you don’t think you know much about how it works. You probably know more than you realize, if you’ve been working with film since the ‘80s, because many digital techniques imitate analogue processes—sometimes simple and familiar ones like using color filters with B&W to change the contrast of the image, and some rather complex ones like unsharp masking, which is a rather advanced graphic arts technique that was originally done with layers of film in register.

So say you filter a color image with a physical glass filter on the lens, shooting color film, and digitally convert it to B&W. Will it look the same as if you had used B&W film and printed it more or less “straight”? Well kind of. The sky is blue, and the grass is green, so they’ll be darker, as you would expect, but different B&W films react a bit differently to filtration because of differences in spectral sensitivity and such, and the same should be true of color films. Try it, and see if you like the look. Ideally, if you have more than one back, you could compare results with a color and a b&w film.

I don’t know how much time the lab owner is willing to give you, or how much you’re willing to pay him for editing, but he could probably show you what Kevs is talking about above—how to take a straight color image and apply digital “filtration” when converting it to B&W without using a physical filter on the lens.

 

[Paul Manuell]

If you’re sitting with the lab owner at a computer deciding how to print your images, then you’re doing digital image editing, even if you don’t think you know much about how it works. You probably know more than you realize, if you’ve been working with film since the ‘80s, because many digital techniques imitate analogue processes—sometimes simple and familiar ones like using color filters with B&W to change the contrast of the image, and some rather complex ones like unsharp masking, which is a rather advanced graphic arts technique that was originally done with layers of film in register.

So say you filter a color image with a physical glass filter on the lens, shooting color film, and digitally convert it to B&W. Will it look the same as if you had used B&W film and printed it more or less “straight”? Well kind of. The sky is blue, and the grass is green, so they’ll be darker, as you would expect, but different B&W films react a bit differently to filtration because of differences in spectral sensitivity and such, and the same should be true of color films. Try it, and see if you like the look. Ideally, if you have more than one back, you could compare results with a color and a b&w film.

I don’t know how much time the lab owner is willing to give you, or how much you’re willing to pay him for editing, but he could probably show you what Kevs is talking about above—how to take a straight color image and apply digital “filtration” when converting it to B&W without using a physical filter on the lens.

With ref. to your first paragraph; I literally have no idea how to do what he does. He just moves and clicks the mouse at a rate of knots that I wouldn't have a hope in hell of being able to replicate given the opportunity. All I do is let him get on with it and see the result, then say a bit darker, bit tighter crop or whatever, and carry on till it's how I like it. If he were to hand the mouse to me and say have a go, I literally wouldn't be able to do a thing other than move the cursor randomly around the screen.

Thanks for the rest of the post; will just give it a go one day and see how it turns out. The option of having 2 backs and swapping them around isn't actually an option at all with my camera.

 

[jtk]

If you use NIK with PS you can click a button that visualizes whatever filter.

 

[glbeas]

Simply ask your computer guy to print the red channel alone. Problem solved.

 

[David Brown]

I'm going to simplify this for you: the answer is no.

 

[darkroommike]

A d-word conversion is easier and then you don't need to filter the original when you shoot it. Hard cutting red filters can fool meters even when shooting panchromatic black and white films, not all meters share the same red sensitivity. If you don't own a computer and a digital editing program you are then at the mercies of your finisher to get the results you want, and you should expect to pay for his time as you experiment. I have shot color slide film through strong color filters just for the heck of it in the past, and one last bit of advice? BRACKET the heck out of it.

 

[Paul Manuell]

A d-word conversion is easier and then you don't need to filter the original when you shoot it. Hard cutting red filters can fool meters even when shooting panchromatic black and white films, not all meters share the same red sensitivity. If you don't own a computer and a digital editing program you are then at the mercies of your finisher to get the results you want, and you should expect to pay for his time as you experiment. I have shot color slide film through strong color filters just for the heck of it in the past, and one last bit of advice? BRACKET the heck out of it.

I'm not at his mercy as I actually sit with him at the computer and watch the changes he does for me, so just tell him as we go along what I want doing. And he doesn't charge me for doing this, only for the film developing and scanning.

 

[BradS]

I'm going to simplify this for you: the answer is no.

An answer so good that it bears repeating.

 

[cowanw]

"what I'm asking is if shooting a colour film with a red filter then converting that photo to b&w gives similar results to shooting with a b&w film and red filter in the first place?"

"I'm going to simplify this for you: the answer is no."
Simple is good but I am at a loss why they will not be the same, choice of B&W conversion algorithm excepted. If only red light from the scene hits either Colour or Black and White film then how is the underlying basic process of exposure of silver halides going to be different?
I have done this (by accident).

 

[grain elevator]

I'm going to simplify this for you: the answer is no.

Please explain how you arrived at this conclusion.

 

[MattKing]

Would taking such a photo then converting it to b&w give the same or similar result as shooting with b&w film and a red filter?

It would only be the same if the two films had the same response to all colours. I don't know that there are two films - one black and white, one colour - that do respond the same way. It may be that the differences are smaller than you care about.

 

[darkroommike]

I'm not at his mercy as I actually sit with him at the computer and watch the changes he does for me, so just tell him as we go along what I want doing. And he doesn't charge me for doing this, only for the film developing and scanning.

Right and do you pay him by the hour as he sits there, does your processor charge you by the hour as he sits there working on your stuff exclusively while everyone else waits? It seems like a poor profit model for a photofinisher. In the past I had one guy that came to our one hour lab (he shot Leica and was a rich doctor, lots of toys, which should already say something about his level of entitlement) and would color and density correct his prints as they came out of the processor. We finally told him that we are not a custom lab and that he needed to find another finisher or he could pay us for all the nitpicks he rejected.