فن التصوير .. المباديء والمنهاج الدرس -٢٣- المرشحات والتصوير بالأسود والأبيض

**Ali Abbass** · 05-19-2023, 01:26 AM

art of photography . . Principles and Curriculum Lesson -23-
Filters and black and white photography

Filters are among the most useful and least expensive accessories in a photographic bag.

Once again, we will start by introducing you to the concepts of filters according to their relationship with black and white film. Once you understand these concepts, you will be able to easily understand the instructions on how to use filters with color films, which we will present later in a lesson on color capture.
The filter makes you able to change the gradient values in your black and white photos.
An example of this is that the appropriate filter can make the blue sky look darker, so that the white clouds stand out with more distinction, and the red filter can highlight a rose against its background. By choosing the right filter, you can often change the appearance of your photo to emphasize one element or another. From here, the appropriate use Filters can help you reproduce the scene either as you see it, or as you want it to appear.

How do filters work:
Filters are usually clear, tinted glass cylinders that can be screw-attached to the front edge of the lens.
To understand how the filters work, we have to look at the light theory. White light is usually made up of three main colors - red, blue and green light - that is, you have mixed red, blue and green lights. Together you get a white light, we're talking about blending the light here, not blending the paint, and what
What you know about mixing paint as a subtructive color does not apply to mixing light as an additive color.
The three aggregate primates
1 - red.
2 - blue.
3 - green.
If you mix red light with blue, you get a fuchsia light (magenta) that looks reddish blue.
And if you mix blue light with green, you get cyan light, a bluish-green color.
As for the filter, it transmits light of its own color, while preventing the passage of light of the remaining primary colors, as follows:
- The red filter transmits red light, and prevents the passage of blue and green.
- The green filter transmits green light, and prevents the passage of red and blue.
The yellow filter transmits yellow light consisting of red light and green light, and prevents the passage of blue.

These are the basic facts about light and filters. They seem a little complicated when you first read them, but they become very simple when you read them again: Now how do we apply these facts to black and white photography? ..

How to use the filters:
- Let us take a yellow filter as an example of what we are about. The yellow filter transmits red and green light freely, but it prevents the passage of blue light, and we mean by the phrase, “prevents the passage of” blue light. It does not allow all the blue light to pass through it, that is, it absorbs some of this light .
The result is that through the yellow filter, less blue light passes through the lens than it would pass into the lens without a filter.

How does this affect a panchromatic film? ? .
When the film is affected by a lower amount of light, less silver halide crystals are affected. This means that in the areas where the yellow filter blocks blue light from reaching the film, these areas will be thinner in our screen—fewer silver halide crystals will turn to silver—and these areas will be darker in the print.
The result: when you have a yellow filter on your camera, this will make blue objects look darker in nature.
Compare these pictures of the sky. The picture, a, was taken without a filter. and image, b, with a light yellow filter
Known as (k1) or (#6), note how the sky in A is an indistinguishable gray. It does not show details within the clouds, but in “b”, by dimming the blue of the sky, it brings white clouds with light contrast and some details appear in it.
Good . The smaller filter blocks blue light. This gives a more opaque image of the blue on our print.

How much blue light does it block? ? The deeper the color of the filter, the greater its effect. For example, the more yellowish your filter, the more blue light it blocks, and the darker the resulting image in our print.

If it had prevented the passage of all blue light, the sky would have appeared black in our filtered image.
Let's see what happens when we use very dark yellow filters. I took photo C,
With a yellowish filter called (K2) or (#8) filter.
Notice how the blue sky tended toward more and more education.
It contrasts lightly with the white clouds even more strongly, and this shows that the deeper the color of the filter, the stronger the effect.

Choose your filters:
Filters are available in almost every color you can think of. Where did you start from?
We recommend that you start with three filters.
Medium yellow (8 #) or (K2). Light green (11 #) or (1×). Red (#25) or (A).

It is interesting to note what happens to the sky when we use a green or red filter.
The image has been cropped. E, with a green filter (1×) or (#11) and the photo. And . With a red filter (8) or (#25).
Notice that the green filter ( #11 ) darkens the sky by about the same amount as the dark yellow filter ( #15 ) . The red filter (#25) turned the blue sky almost black.

What filter should we choose to darken the sky and bring in the details of the clouds?
For more dramatic skies, your choice might be a red filter ( #25 ) . But if your subject is a foreground model, the red ( #25 ) may distort her facial features unnaturally. For a more natural effect when that's what you want, just add an emphasis to clouds in the background. A moderate yellow (#8) would be a better choice, as this will have a slight effect on the skin tones and add a modest drama to the sky.

Review: Remember the basic rules for candidates:

1- To lighten the image of a color. Work with a filter of the same color as long as it conveys that color.
2- To darken the image of a color, use a filter that prevents the passage of that color.

Candidate factors:

Since each filter prevents some light from passing through, the film will receive less light than it would if there was no filter. The result is that if you change the scene with a separate light meter, and use the results to set your exposure, this exposure will be underexposed. This is because the light that reaches the film is less than what the meter indicates.
From here, and in order to make the exposure properly, using a separate light meter, you have to compensate for the light that the filter prevented from passing, as you depend on an adjustment called the filter factor (*).
This, and the instruction sheet that comes with the filter informs you of its factor. If it indicates factor 2 when you use pan film in daylight, this means that the case requires twice the normal exposure, provided that you work with panchromatic film and expose in daylight, because Filter factors vary according to the light source - Nornhar or tungsten - and the type of film - ortho or pan. They also vary according to the strength and color of the filter itself.

You double your exposure when you widen your aperture one stop. From here, if your normal exposure is f/8 at 1/60 and you're working with a filter that has a factor of 2, you can compensate for the filter by either expanding one aperture - to f / 6.5 - or by making your shutter speed slower by half - to 1/30.
Here are the Pan-Film filter factors that approximate the three filters we are discussing:

The filter factor that the manufacturer gives is really just a starting point for determining your exposure. Many professionals say that filter factors are often too great and the result is a photograph they consider to be overexposed.
However, overexposure reduces the effectiveness of the filter as long as the film receives more light that you are trying to prevent. Therefore, you have to adopt care and caution not to overexpose when you are using filters.
Once you get a filter, test it, take a roll with varying exposures, taking the filter factor mentioned by the manufacturer as a starting point, and then find out for yourself which factor gives you the results that you like the most. This is your personal factor for the candidate, stick to it.

**Ali Abbass** · 05-19-2023, 01:28 AM

Filter factors and calibration through the lens:
Do you need a filter factor with a through-the-lens expression system? .
The answer is no, in general. The meter in an (SLR) camera reads the light after it passes through the filter, and this means that it automatically compensates for the filter.
This, and some photographers feel that when using | A strong filter, a significant shift occurs from the natural light mixture on the basis of which the meter was expressed, and thus the meter loses its ability to respond accurately. Therefore, they prefer to measure the light after implicit adham before placing the filter. Then after reading the exposure like that, they mount the filter and apply the filter factor.
What should you do? ? .
You can trust the meter through your lens in general. This is especially true if you follow our advice and pick up a selection language with each filter - that way, you can see, and compensate for, any misreading of the meter by any filter and change the aza number on the camera's expression system - smaller numbers for more exposure, numbers Bigger for Less Exposure - This is an easy way to make this adjustment.

A final word on using filters with an SLR camera. You may have difficulty focusing through a very dark filter such as red (A) or dark red (F). Here is a trick that professionals adopt. Remove the filter, and replace it with another open one - a sky light filter, for example - while you are focusing, as the filter glass refracts the light a little. So if you focus without any filter at all, then install an (A) or (F) filter on the shot, you may be somewhat out of focus and by focusing through a transparent filter, you get the same refraction as with the (A) or (F) filter. . Naturally, you have to adopt caution so as not to change your focus when you remove the illuminator filter (*) screw-on and install the (A) or (F) screw-on as well.

Filter parameters:

When purchasing a filter for your camera, make sure it is the correct size and has threads that will fit on your lens. It is unfortunate that different companies that manufacture cameras produce lenses with different diameters. An example of this is that standard lenses or Limpus - Zuiko - have a size of 52 mm, and Canon has a size of 55 mm, and so on. From here, the candidate concerned with a lens - or Any other accessory attached to the lens - to be of the correct size to fit the lens itself.

So when buying a filter, specify the specifications of the type of lens it will be mounted on. If possible, test the filter before purchasing it to be sure it will fit your lens and the threads.
All is not lost, however, if you have a filter for a 49mm lens, and you also want to use it on a 52mm lens. You can buy an adapter ring to be attached to a 52 mm lens, and it has screws in which the 49 mm filter can be attached. Since this type of adapter ring holds a filter that has a smaller diameter than the diameter of the lens, it is called a reducing ring (*). And vice versa if you have a filter designed for a 52mm lens.
I wanted to use it on a 49 mm lens, using a lifting ring (*) that is mounted on the smaller lens and accommodates the larger filter. There are many different sizes of lowering and lifting rings. Again, we recommend that you try one on to make sure it fits before you buy it.

One last point, do not confuse the lens diameter, which is measured in millimeters, and the focal length of the lens, which is measured in millimeters as well. Nikkor standard lenses for Nikkor cameras, for example, have a diameter of 52 mm. This is true for a 28mm wide angle lens, a 50mm normal lens, and a 200mm telephoto lens.

Filter codes:

The names of the filters may seem confusing at first. The particular bright yellow filter may be referred to as - Ratten Filter #6, Filter #6, Filter (K1) or (#6) These all refer to the same filter, so let's simplify the confusion.
Ratten & Wainwright Ltd. was an English manufacturer of filters that was acquired by Kodak in the early part of this century. When Kodak took control of the company, it inherited another code system for the colors of the filters that the English company used, which is as follows:
A - red
k - yellow (formerly G)
B - green
L - purple
C - blue
N - strong green
E - orange
p - blue-green
F - strong red
R - deep green

And with Kodak developing more filters in its Ratten department, it has lost its name - Wainwright. With the shuffling process, they added numerical extensions to define the different filters. From here it was that there were multiple different filters symbolized by the expression K3 ... K2 ... k1 ... etc., and these symbols were called Ratten symbols (*).
Other filter producers have their own code systems but because of the rule of Kodak Ratn in this field, they usually have a code, Ratn, that matches theirs.
Hence, the other major American filter producers—Teffen and Harrison & Harrison—and the major foreign producers—Bw in Germany and Hoya in Japan—refer to their filters by their own symbols as well as Ratten symbols.

In the early sixties of this century, Ratten introduced a new numbering system, whereby (k1) was called a filter (6 #) as well, and thus the symbol, Ratten, for this light yellow filter became (6 #) 1 K or (k1) 6 , and then -Ratten, in recent years abandoned the old symbols entirely, this filter is denoted by just (6 #).
And since many filters still use the old symbol as they use the new one, then the relevant publications refer to both symbols. We intended to use them together in this seminar, and for your reference, we included a table of the old and new symbols with the topic⏹

Next lesson Types of filters and when to use them

فن التصوير .. المباديء والمنهاج الدرس -٢٣- المرشحات والتصوير بالأسود والأبيض

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