When I was a youngster, my father was the family photographer. He was a good photographer with an understanding of both the aesthetics and the technical aspects of photography. My mother wasn't as good with a camera as he was. Long after she died, I found hundreds of pictures that she'd taken when she was a young woman, many years before she had met my father. I had never imagined what a prolific photographer she had been. This made me realize that my father, although he was a good photographer, never really seemed to be that enthusiastic about it.
At the age of 8, I was thrilled to get my first camera. Not surprisingly, those early pictures weren't very good.
When I was in my late teens, I started making an effort to become better at photography. One thing that I did was to study the pictures in magazines, primarily National Geographic. I tried to understand why their photos were better than mine.
Going through old family photos, I realized that the pictures are mostly of birthdays, holidays, vacations, and such. There are very, very few pictures of ordinary activities in ordinary days such as mowing the lawn or washing the car or playing in the yard. When I'd take ordinary pictures of my brother or sister or our cat in the backyard, I was told that I was wasting film that I should be saving for whatever the next special occasion was. I wish that I had more pictures of everyday life instead of just special occasions.
Limitations of Black and White from Color
Introduction
One myth about doing B&W, which has become more prominent with the prevalence of digital photography, is that you can get whatever B&W effect you want after you have a color image. That's not necessarily true.
Spectral Information Loss
Supposedly, you can choose from a selection of techniques (they doesn’t have to be digital) such as the channel mixer and achieve whatever you want. Although a lot of good results can be had that way, it’s not true that you can get whatever you might want or necessarily achieve the look of some particular B&W film. Why not? The reason is that most of the spectral information of the scene is lost when the image is made. Typically, the spectral information is reduced into 3 spectrally overlapping channels: red, green, and blue (they HAVE to overlap spectrally to get a proper image from a camera... but that’s another story). Once that happens, there’s no going back and getting the missing spectral information. Consider that green and red make yellow, don’t they? Well, yes and no. The red and green light rays don’t somehow mix together and make a light ray of yellow wavelengths. What happens is that our eyes perceive seeing red and green simultaneously as being yellow. Since there’s a range of single wavelengths that we also see as yellow, there’s no way to know if a yellow object is sending yellow wavelengths of light our way or if it’s sending red and green light at the same time. Well, yes, it is possible to determine that but not just by looking at it. Since cameras are generally designed to more-or-less mimic the way our eyes work, if an object in a photo is yellow, there’s no way to know if it sent yellow wavelengths of light into the camera or if it sent red and green wavelengths into the camera simultaneously. (Also note that there’s a similar effect using color film. This doesn’t happen only with digital.) So, what does all this have to do with making B&W from color? B&W film has a spectral response curve. For example, it might be more sensitive to yellow wavelengths than red or green wavelengths. Since a color camera can’t tell the difference between yellow wavelengths and simultaneous red and green wavelengths, it’s impossible to recreate the look of that film with a digital photo editing program or in the darkroom. This isn’t just a problem with red, green, and yellow. I just used that as an example. I'm not saying that there is always this problem. I am saying that there is the risk of this problem. So, there's no way to be certain you can get the effect you want without doing some testing. For a lot of ordinary pictures, this isn't a big thing to worry about but you should keep it in mind.
Color Space Effect
Another limitation in converting color to B&W is color space. You might think that color space wouldn't matter with a B&W photo but it can. The color space of digital photos is usually sRGB or sometimes Adobe RGB. (There are other color spaces but they are far less common in photography.) The limits of what colors can be reproduced-- the “gamut”-- will have an effect on the B&W conversion. (Color films have a color space, too, but I’m not going to get into that.) If you want to convert your color photos to B&W, it’s better if you start with the biggest color space. This is often Adobe RGB. (Keep in mind that a digital image that has a bigger color space does not have the capability of more colors. The number of colors is determined by the bit depth. A bigger space with the same number of bits means that the steps between colors are larger.) Although, in most photos, the difference between sRGB and Adobe RGB is noticeable, it is not overwhelmingly huge or anything. It’s just that you should use Adobe RGB for your B&W conversions instead of sRGB if you have those two choices. If you’ve got a choice that’s bigger than Adobe RGB, use it. If you’ve got a choice of no color management, you might want to give that a try but it may not give you the most natural result. (Of course, sometimes the natural result isn't what you are after.)
If you can shoot raw, you might have a B&W option in the raw converter. Not all raw converters have a B&W option, although you may be able to reduce the saturation to zero, so you are generally stuck with making a B&W from a converted file that has been squeezed into a color space even if you shoot raw... and a lot of cameras don’t offer a raw option anyway.
Also, the absolute maximum of the color gamut depends on the camera’s design. Some have a greater capability than others. However, when a particular color space is selected, such as sRGB, the limits-- but not necessarily the accuracy-- of the colors are the same for all cameras.
This shows the difference between a B&W made from sRGB and one made from Adobe RGB.
Place your mouse over one of the buttons below to see that photo (no need to click but you might have to wait for a moment for the download to complete).
You can see that the difference between the two B&W images is subtle but visible. In-Camera B&W
Most digital cameras have a B&W option but I’ve yet to see any manufacturer state how the conversion is done. I don’t mean that you shouldn’t use it if the result provides an image that you like. I just think it would be nice if we were told what was taking place. Also, some cameras prevent setting the white balance when B&W is selected. This isn't right. White balance matters with B&W! Color in the light source is similar to using a colored filter in front of the lens.
Conclusion
Am I trying to say you should use B&W film if you want B&W pictures? Not at all! With digital, we have a lot easier control over things than we ever had with film. I’m just trying to point out some of the limitations that exist when you do a color to B&W conversion. B&W film has its own set of limitations that I’m not going to write about. Just keep in mind that it might not be possible to get the precise look of your favorite B&W film by using the channel mixer (or whatever) from a color image or to get some special look that you had in mind.
Another idea that isn’t exactly right is that, with digital photography, filters on the lens are no longer necessary with the possible exception of a polarizer, neutral density, or infrared and maybe, grudgingly, a gradient filter. Of course, it’s always been possible to do many kinds of filter effects after the fact not just since digital photography. It’s just that doing them in the darkroom is a lot more trouble than clicking a mouse.
It’s true that a lot of filter effects can be done digitally but that isn’t necessarily as good as using a filter on the lens. When a filter is used on the lens, typically the filter factor is taken into consideration when the exposure is determined. When a filter effect is applied digitally, that filter factor doesn’t magically go away. The image editing program must do a virtual sensitivity (“ISO”) increase in order to deal with the filter factor-- keeping the apparent brightness of the image constant. That increases the visibility of noise in the image, especially in the darker areas. If a filter is used on the lens at the time of the exposure, there’s the possibility that the exposure can be increased by changing the lens aperture or the shutter speed rather than increasing the ISO setting.
Another problem with digital filter effects has to do with the spectral information loss once the scene is reduced into the RGB channels. This is similar to what I discussed above about B&W from color. In many cases, though, this isn’t much of an issue. There are some filters that can’t be simulated digitally but many photo filters can be.
There is a possible down side to using a filter on the lens: degraded image quality. This isn’t necessarily a loss of resolution. One thing that happens is that the bright parts of the image manifest themselves as ghosts in other parts of the image. This is the result of reflections off the filter. These ghosts maintain the same linear dimensions as the real image so that’s a very strong hint that the culprit is a planar surface. This is something that becomes more of a problem with night photography because those kinds of scenes are more likely to have lights here and there and a lot of dark areas. (You can often see ghost images in TV or movie scenes that are shot at night of a car driving by. The headlights on the car will appear as a ghost image that moves along the frame in addition to the real image of the headlights.) The problem always happens, though. It’s just that with most photos the real image overwhelms the ghosts so they aren’t noticeable. The problem can be minimized, or even made invisible, with a filter that has very high end coatings. Lens filters that are sold as “digital” have (or should have!) better coatings on them than the filters that have been used for film because digital cameras are more susceptible to reflections in the optical system. The reason is that a digital “sensor” is much shinier than film and will reflect a lot more light back into the optical system than film would.
Here is an example of a ghost image from a filter with low-end coatings:
I've cleaned my camera's sensor. It wasn't really that bad. Some of the things I've read online about this make it sound like it's trickier than brain surgery and only the most sophisticated and highly trained people should be doing it. My thought was that it likely doesn't require years of training at the best schools to do this.
I used the Photographic Solutions swabs and E2 Eclipse solution. (They have a couple of formulas depending on the camera's sensor since they can't all tolerate the same chemistry.)
I got the stuff at Keeble and Shuchat in Palo Alto, California. The swabs are sold separately from the fluid. There are 12 swabs and 2 fluid ounces of cleaning solution. The cost was $52.55 including tax. (They would clean my camera's sensor for me for $40. I asked them how they did it and they use that same stuff if just brushing won't work.)
After the first cleaning, the result was vastly worse than when I started. This was disappointing but not really a surprise. I expected that I would get off to a couple of false starts before I learned the technique. It took 4 cleanings to really get it right. Since you never want to reuse a swab, I went through 1/3 of the package to learn. They don't tell you this in the directions probably because they don't want to discourage people from buying the product. I think that's a mistake because I've read plenty of comments online written by people who made things worse after they tried this and they tell people not to use the product.
The swabs are little fabric covered plastic spatulas that are the same width as the sensor's height. You moisten it with the fluid, drag it all the way across the sensor, turn it over to the clean side, and drag it the other way.
Here's what I learned so if you need to do this you might get a good result a little quicker than I did.
- When you start the swab, don't have it off the edge of the sensor because that can cause the fabric to become ragged and leave pieces of itself behind or drag debris that's off the sensor onto it. The photosites are microscopic so it doesn't take a very big piece of debris to show in the photos.
- Don't lift the swab up until you're all the way at the end. If you do, you could get a result that's similar to what happens when you wipe a squeegee across your car's windshield and lift it up leaving a line of fluid. With the sensor swab, I got a line of debris.
- It may not be necessary to do a double wipe. If the sensor isn't too dirty, just once across may be enough.
So, that was my experience. It wasn't really that bad. If you're careful and have a reasonably steady hand, you should be able to so this. Don't be upset if you need a few practice efforts before you finally get the hang of it. It's not easy to learn something 100% on the first try! Just don't forget to use a fresh battery or power adapter so the camera won't close while you're cleaning.
Introduction
This article will describe a way of achieving-- or hopefully improving-- white balance when things went awry during the actual picture taking. In some cases, the result won’t be perfect but it may provide a reasonable starting point that can be used for manual fine-tuning.
Shooting raw can sometimes be a good idea if white balance is not easily set at shooting time. However, I’ve never seen a raw converter that can do all the things that a good image editor will do. In some situations that extra capability exceeds the corrections that can be made with raw. Also, an image editor will work with most image file formats. Besides, a lot of cameras don’t offer raw.
The methods I’m going to describe are based on the usual gray dropper in the levels/histogram adjustment (some programs require the use of curves rather than levels to do this). What can sometimes be helpful is the way I alter the image before I apply the dropper or, in the case of the wrong setting on the camera, returning to the scene of the error. This involves using not only levels but also layers. If this is going to make your head explode, please make sure that your affairs are in order before proceeding! Really, it isn’t that hard. This isn’t brain surgery. The steps I describe here are more or less for a generic image editor. However, some very simple image editors will not let you do this at all. It’s up to you to know how to use your own system.
Wrong White Balance Setting
If you’ve shot non-raw pictures (without a neutral reference in the scene) with your camera set to the wrong white balance, such as using the tungsten setting when you should have used sunlight, you can fix or at least improve your pictures.
The best way to do this is to go back to the location, assuming the lighting is the same, with your camera and a neutral gray card. It doesn’t have to be 18% gray. (A good argument can be made for it to be brighter than 18% because the signal-to-noise ratio will be higher.) Set the camera to the same wrong setting that you used (it likely will be easier later if it’s also set to the same resolution setting that had been used). Take a photo of the neutral card with it positioned in the same place as the subject and with the camera in the same place as before. If it’s a bit of an effort to get back to this location, you should consider taking a number of shots with the neutral gray card in various orientations. If you have access to a neutral ball or cube, use it instead of or in addition to the card. Now that you have a photo of something you know is neutral and that was photographed with the same wrong setting, you can use that to correct your pictures! In a way, you have put a neutral card into the scene. As long as the lighting is the same and the camera settings are the same, you can take the photo of the neutral card at any time.
- Open the photo of the neutral card in your image editor.
- Use the Select tool to select only the interior of the gray card.
- Perform an average blur of the selection.
- Deselect.
- Create the Levels/Curves adjustment layer.
- Choose the gray dropper in the Levels/Curves adjustments.
- Click the dropper in the gray card area that you blurred.
- Click OK.
You’ve now got a layer that will correct the white balance or at least get it close. To use this to fix your other photos, you can drag or copy this layer onto them. Depending on your image editor, you might be able to automate this process if you’ve got a lot of pictures that need fixing or you might be able to save the setting and recall it later.
If you can’t return to the location, you might be able to find a place that has similar lighting and use it instead.
Difficult White Balance
Most digital cameras allow you to set a custom white balance. Although that is very often an excellent method, it isn’t always practical so the auto or another setting is used. Sometimes, you’ll find that it didn’t go well when you look at your pictures later. You may not have anything neutral in the image to use as a reference or it may not be illuminated in a way that makes it useful. You may be able to correct the white balance using a digital version of what we sometimes did in the darkroom (no doubt there are still a few people out there in darkrooms doing this). One technique in the darkroom was to assume that the entire image averaged to a neutral gray. However, sometimes a large part of the scene would have a lot of a single color, such as a red car occupying a lot of the frame, and this would fool the system. This was called “subject failure” although the failure was actually the technique. We can use this method digitally with the advantage that it’s rather easy to avoid subject failure.
- Open the image in your image editor.
- Duplicate the layer.
- Blur that new layer as an average.
- Create a new adjustment layer for Levels or Curves depending on your editor.
- Choose the gray dropper.
- Click the gray dropper on that blurred image.
- Click OK.
- Make the blurred layer invisible (typically click on the eye in the layers palette so it goes away).
You’ve now got a picture that was white balanced as if the entire scene averaged to neutral. This isn’t always the best balance, of course, but it can sometimes provide a good starting point for manual tweaking.
What about subject failure? The way to avoid that is to use the selection tool-- in the duplicate layer-- to select everything in the scene except that red car or whatever. The average blur will now include everything except that car. Deselect after the blurring. Clicking the gray dropper in the blurred area will set the white balance according to everything except that car.
Gray Cards
Real gray cards aren't that expensive but you can get something close, although smaller, for free.
The paint Laura Ashley Home "Chimney Sweep" is a reasonably good 18% gray. You can get a sample chip for free at Lowe's.
For a range of light gray to dark gray, try a 6-sample chip set of Glidden "Snowfield / Universal Grey / Veil / Granite Grey / Obsidian Glass / Dark Secret". A sample of this set of colors is available on one card for free at Home Depot.
(Lowe's and Home Depot are building supply stores in the USA. I don't know if they are in other countries.)
I've checked these samples against my Macbeth color checker and Kodak gray patches. Although not perfect, they are reasonably close. I got some and cut them to about the size of business cards and keep them in my wallet. There can be a slight color variation from one sample to another but, so far, this hasn't been much of a problem with the ones I've had. They are better than nothing and you can't beat the price!
Looking for a fluorescent lamp that's suitable for photography work? Good luck!
Although you might be able to find a fluorescent that will meet your needs, as far as I know, none of them are really that great. The trouble is that they have a "lumpy" output. That is, the distribution of the colors has spikes in it. This can cause metamerism in some situations which can be difficult or even impossible to alleviate. Whether this will a problem for you depends on the particular circumstances.
Despite the hype of some manufacturers and well intentioned amateurs, the color temperature is a poor indicator of the characteristics of a fluorescent lamp. It is only truly meaningful for a black body radiator which is what a filament (regular light bulb) essentially is.
Fluorescent lamps generate their light by using phosphors that glow in the UV that is given off when mercury vapor is ionized. The phosphors fluoresce, hence the name fluorescent lamp. The fluorescence is not continuous across the spectrum. By using various phosphors, the output can be made to resemble daylight, especially to easily fooled human vision, but it is not truly daylight and sometimes photographic equipment will reveal the limitations.
Another often overworked indicator of color quality is the color rendition index, CRI. A regular tungsten lamp has a CRI of 100. Some fluorescent lamps have a CRI that is in the 90s. This index doesn't provide enough information, either.
I know for a fact from first hand experience that it is a mistake to assume that a good color temperature number and a high CRI will reliably produce a good result. We wasted a lot of time and resources by believing that a particular (and well known) photo lamp producer's fluorescent products were of good characteristics. After a lot hair-pulling, we determined that the problem was the poor spectrum of the lamps even though they had a near perfect Kelvin rating and very high CRI. After replacing them with properly balanced, pricey, heat-generating halogen tungsten lamps, the results were VASTLY improved.
The only thing that really tells the story of a lamp's color quality is a spectral analysis of its output. Few lamp manufacturers provide this information. From discussions I've had with some of them, many of them don't even understand this themselves. Others apparently don't provide it because they know it will make their products look like trash.
Try this experiment. Setup a still life that will resemble what you usually intend to photograph keeping special attention to colors that you expect. Photograph it with tungsten lamps and then with fluorescent lamps. Be sure to set the white balance correctly each time. When you look at the results, you can judge which, if either, you prefer. (Be sure that you are judging the colors and not how soft and diffuse the light is, assuming that color accuracy is what you are concerned with.)
This picture shows what you get with several different lenses on a camera that has a so-called APS-C size sensor. The widest is 12mm which is the entire image.
This image is 721x495 pixels in size.
(This scene is at Disney World in Florida. The particular spot is along the walkway between EPCOT and Disney Hollywood (MGM) Studio.)
One thing that has caused (and continues to cause!) a lot of aggravation is underexposure when using an SLR. There can be a lot of causes of this. It seems that a lot of people are quick to jump to two conclusions about the reasons:
1- The camera's metering is trying to be helpful and not clip (blow) the highlights.
2- The camera is not very good and fails to even measure up to a cheap point and shoot.
Although those two reasons might right sometimes, there is another possible reason that doesn't get discussed as much as it should: light entering the eyepiece. Many cameras meter the light that hits the focusing screen in order to determine exposure. The meter doesn't know if that light came through the picture taking lens or through the eyepiece. This can cause a very noticeable error depending on the circumstances. It can be worse if you wear glasses because they will tend to make the gap between you and the eyepiece bigger thereby allowing more light into the eyepiece.
You can easily determine how much of a problem this is. It's best to put your camera on a tripod for this little check. Simply meter a scene with your eye at the eyepiece and then with your hand completely blocking the eyepiece. In many situations, there won't be a difference but don't be surprised if, sometimes, the difference is considerable.
A lot of cameras come with an eyepiece shield that can be put on to cover the eyepiece. Although this is, obviously, not always practical, it should be used when possible. If you aren't able to do that, just try the check I described above. Note the error and use the exposure compensation to correct the meter. Don't forget that the compensation has a very good chance of varying as you move the camera or as the lighting changes. Also, when I've been in situations where this was a problem, I've been able to reduce the error to minimal levels by wearing a brimmed hat.
This problem was solved decades ago. Why we have to continue to live with this is a mystery to me.
Much of this information was assembled over a period of time from various sources that I have long since forgotten.
Hopefully, I haven't made any mistakes putting this page together. If you find any, please let me know.
• Basic Exposure This is often called the "sunny 16" rule. I always had trouble remembering this. Is it "sunny 16" or "sunny 11" or what? I finally got it into my mind when I started to think of it as the "sweet 16" rule... not that "sweet" has anything to do with it other than that I think it's easier to remember.
In bright sunlight with average subjects, the shutter speed is:
1/ISO seconds at f/16
• Relationship Between Light and Exposure Here's the relationship between f/stop, film speed, shutter speed, and light.
(Note that a shutter speed such as a thirtieth of a second is expressed as 0.03333 not 30.)
fstop^2/shutter_speed=foot_candles*ISO/25
ISO=1/(light energy that produces an optical density of 0.6 above base & fog) units of ergs/cm^2 of film surface
• Field of View The Field of View, "FOV", can be computed from the lens focal length and image size. Note that this doesn't work for fisheye lenses.
(Example: With a 35mm camera and 50mm lens, the vertical FOV is 27º, the horizontal FOV is 40º, and the diagonal FOV is 47º.)
FOV = 2*ATN(image_size/(2*focal_length))
• Color Correction (CC) To and From Percent Digital editing software sometimes makes color changes using percent. Percent change can be converted to CC equivalent and vice versa.
Note that the signs are opposite. The colors need to be, too. For example, if you want to add 10 CC yellow, the formula gives about -21%. That means you need to subtract 21% blue.
(Note that the profile, rendering intent and such can cause variations that are not taken into account with these formulas. In practice, these formulas should be considered an approximate starting point.)
• Mired Values Mired (MIcro REciprocal Degrees) values are used with filters, light sources, films, and some digital cameras to achieve a desired color balance. If more than one filter is used, the mired values of those filters are added. Mired is sometimes abbreviated as MK.
mired_value=1000000/color_temperature_in_Kelvins
• Exposure Value (EV) Exposure Value isn't used as much as it used to be but sometimes this information can be useful. It's defined such that EV0 is f/1 at 1s.
(Note that a shutter speed such as a thirtieth of a second is expressed as 0.03333 not 30.)
• Guide Number (GN) Flash Guide Number is used for determining what f/stop to use. Make sure that you are using the correct GN for the distance units that you are using (typically feet or meters).
Conversion of GN from one ISO to another ISO can be done.
• f/stop Changes Exposure factor for changing the f/stop or vice versa.
f/stop change for a change in shutter speeds.
f/stop change for a change f/stops.
(Note that a shutter speed such as a thirtieth of a second is expressed as 0.03333 not 30.)
• Lenses and Film/Sensor Formats The normal focal length lens for a particular camera format is equal to the length of the diagonal of the frame.
The "factor" for the equivalent focal length for the same magnification for a full-frame 35mm (135 film size) camera can be calculated for a different camera format. (The square root of 1872, which is exact, is about 43.3. The square root of 2.902, which is an approximation, is about 1.7.
The normal focal length lens for a full-frame 35mm (135) camera is those square roots.)
normal_FL=SQRT(height^2+width^2)
35mm_equivalent_factor=SQRT(height^2+width^2)/SQRT(1872) with measurements in millimeters.
35mm_equivalent_factor=SQRT(height^2+width^2)/SQRT(2.902) with measurements in inches.
• Neutral Density (ND) Filters The filter factor (exposure factor) can be computed from the ND number and vice versa. The percent transmittance can be computed. (The ND number is typically something like 0.6 but could be any positive number. A number of 0 would mean that the filter has no density-- it's completely clear. A negative number would mean that the "filter" is an image intensifier-- which isn't too likely!)
The f/stop required with a filter can be computed from the f/stop without a filter and the ND number; similarly, the shutter speed. Also, the new f/stop or shutter speed if the filter is changed.
When ND filters are stacked, add the individual ND numbers to get the total ND result.
(Note that a shutter speed such as a thirtieth of a second is expressed as 0.03333 not 30.)
• Shutter Speed Changes Exposure factor for changing the shutter speed or vice versa.
Shutter speed change for a change in f/stops.
f/stop change for a change shutter speeds.
(Note that a shutter speed such as a thirtieth of a second is expressed as 0.03333 not 30.)
• f/stop, f/stop Sequence The f/stop is the focal length of the lens divided by its diameter. Note that with complex lenses, it may not be possible to do a simple measurement and calculation to get the correct answer but the basic idea is the same.
The sequence is based on the area in the lens that allows light to pass through. If the area is doubled, then, obviously, the amount of light that hits the film/sensor is doubled. Because area depends on the square of the radius, doubling the area means increasing the radius by the square root of 2 which is about 1.4.
Some of the standard full-stop f numbers are: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22.
The typical half-steps are: 1.2, 1.7, 2.4, 3.4, 4.8, 6.7, 9.5, 13, 19. Obviously, these are to be inserted between the full steps in the list above.
The typical third-steps are: 1.1, 1.2, 1.6, 1.8, 2.2, 2.5, 3.3, 3.5, 4.5, 5.0, 6.3, 7, 9, 10, 12.5, 14, 18, 20. These steps are to be inserted between the full steps in the above full-step list.
If you do the calculations, you will find that these "typical" values aren't exactly what would be expected. I don't know what the reason is for that. If anyone knows, I'd appreciate it if you'd let me know.
fstop=focal_length/diameter
fstop_sequence=2^(n*step_size/2) where n, which can be positive or negative, is a step in the sequence This will generate a list of f/stops:
INPUT step_size
FOR n= -10 to 10 ! arbitrary range
LET fstop=2^(n*step_size/2)
PRINT fstop
NEXT n
• Shutter Speed Sequence The shutter speed sequence is designed to double or halve the length of the exposure from one shutter speed to the next depending on whether the change is to a slower or faster speed. This makes a change of one stop. (Many cameras are capable of intermediate shutter speed settings.)
For example, 1/250 is twice as long as 1/500. If the exposure time is doubled, then, obviously, the amount of light that hits the film/sensor is doubled.
There is some error in the sequence that's used. For example, 1/60 isn't quite twice 1/125. The difference is not significant for normal photography.
Some of the standard full-stop speeds, in seconds, are: 60, 30, 15, 8, 4, 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/8000, 1/15000.
idealized_shutter_speed_sequence=2^n where n, which can be a positive or negative whole number, is a step in the sequence
This shows the difference between a B&W made from sRGB and one made from Adobe RGB.
