What is the Bit Depth of an Image? | Image Bit Depth Explained | 8-Bit vs. 16-Bit

Summary

In this video, John Ross from The Art of Retouching Studio discusses the impact of bit-depth on image tonal range. He explains that while 8-bit is sufficient for most digital media, professionals often opt for 16-bit to access a broader color spectrum, crucial for complex images like sunsets. Ross demonstrates how higher bit-depths reduce banding and improve color transitions, though he also acknowledges that for many images, the benefits of 16-bit may not be visibly significant on standard displays or in print.

Takeaways

• 🖼️ Understanding bit-depth is crucial for managing an image's tonal range, which affects both digital and print outputs.
• 🔘 Tonal range in images is described from absolute black (0%) to absolute white (100%), with various shades of gray in between.
• 🌈 Color images use RGB channels, where each channel represents a color and contributes to the overall image when combined.
• 🔑 A pixel is a single data point containing color and luminance information, with accuracy determined by bit-depth.
• 🎛️ Photoshop defaults to 8-bit images, suitable for web and digital media, but this can limit color data, especially from RAW files.
• 📈 Bit-depth defines the number of shades of gray from black to white, with 8-bit offering 256 levels per channel, totaling 16.7 million colors.
• 💡 Professionals often use 10-bit or 12-bit displays and cameras to capture more color data, which can be edited in Photoshop as 16-bit for smoother gradients.
• 🆚 Higher bit-depths, like 16-bit, provide more color steps, reducing banding and allowing for more detailed image adjustments.
• 🌅 Real-world examples show 16-bit images handle complex gradients better than 8-bit, maintaining smooth transitions without banding.
• 🤔 Despite the benefits of 16-bit, the presenter suggests that for most images, 8-bit is sufficient, and the extra color depth may not be visibly noticeable on typical displays or in prints.

Q & A

What is the primary focus of the video by John Ross from the Art of Retouching?

The video primarily focuses on explaining how the bit-depth of an image affects the tonal range of an image, which is crucial for photographers and retouchers to understand for both screen display and print.

What is the tonal range in terms of grayscale?

The tonal range in grayscale goes from absolute black (0%) to absolute white (100%), with various shades of gray in between, such as 75% gray (three-quarter tones), 50% gray (mid-tones), and 25% gray (quarter tones).

How does color affect the tonal range when discussing bit-depth?

When color is introduced, the tonal range is expanded into RGB (red, green, and blue) channels, each having its own tonal range. This allows for a combination of colors to create a full-color image, increasing the potential tonal range.

What is a pixel in the context of digital images?

A pixel is considered a single data point that contains information about color and luminance. The accuracy of this information is determined by the bit-depth of the data.

Why does Photoshop default to 8-bit for image editing?

Photoshop defaults to 8-bit because it is suitable for most digital media and websites, and it is compatible with the 8-bit display commonly used in devices.

What is the difference between 8-bit and 16-bit in terms of color information?

8-bit allows for 256 levels of information per channel, resulting in 16.7 million colors, while 16-bit provides 65,000 levels per channel, supporting 281 trillion colors, offering a much wider color range and smoother gradients.

What is the practical benefit of using 16-bit over 8-bit in image editing?

Using 16-bit provides a greater depth of color information, which can prevent banding and allow for more flexibility in editing without losing tonal details, especially in images with large gradients.

Why might a professional retoucher choose to work with 16-bit images?

Professional retouchers may choose 16-bit images to access the additional color data captured by high-end cameras, which can result in smoother gradients and more detailed images, especially important for high-quality prints and large-scale reproductions.

What are the limitations of 32-bit images in Photoshop?

While 32-bit images can handle an extremely high color range, they are primarily used for creating HDR images. They also present challenges in Photoshop as many features become inaccessible or non-functional at this bit depth.

What advice does John Ross give regarding the choice between 8-bit and 16-bit for most photographers?

John Ross suggests that for most photographers, 8-bit is sufficient unless they are dealing with images that have severe gradients, like sunsets, where 16-bit would provide a smoother gradient without banding.

What is the significance of bit-depth in relation to image resolution?

Bit-depth is significant as it determines the color information and tonal range of an image, which can impact the perceived resolution and quality, especially in areas with subtle color variations.

Outlines

00:00

🖼️ Understanding Bit Depth and Tonal Range

John Ross from the Art of Retouching Studio explains the concept of bit depth and its impact on the tonal range of an image. He emphasizes the importance of understanding bit depth to avoid Photoshop's default settings that may not be suitable for print. Tonal range is described as the spectrum from absolute black to absolute white, with various shades of gray in between. Each shade is referred to as a step, and the number of steps is determined by the bit depth. Bit depth is crucial as it dictates the accuracy of color and luminance information in an image. Photoshop typically works with 8-bit images, which are sufficient for digital media but limit color data. Professionals often use higher bit depths like 10-bit or 12-bit for better color accuracy and to avoid issues like banding in tones. The video contrasts 8-bit with 16-bit images, showing how the latter can handle more color data and provide smoother gradients.

05:02

🌈 The Advantages of 16-bit Over 8-bit

This section delves into the practical differences between 8-bit and 16-bit images. With 8-bit, there are 256 shades of gray per channel, leading to 16.7 million colors, while 16-bit offers 65,000 shades per channel, resulting in 281 trillion colors. The video uses a technical demonstration to show how 8-bit images can suffer from banding when adjusted, while 16-bit images maintain smooth gradients. Ross argues that while 16-bit provides a significant color advantage, most images do not require it unless they involve complex gradients or high dynamic range scenes. He suggests that for most photography and retouching work, 8-bit is sufficient, but for professional standards and to avoid banding, 16-bit is preferred.

10:04

📸 The Reality of Bit Depth in Professional Photography

In this final paragraph, Ross discusses the practical application of bit depth in professional photography. He acknowledges that while 16-bit offers more color fidelity, the real-world benefits are often negligible for most images, especially considering that most digital displays and print media are 8-bit. He shares his experience of reviewing a large number of images and finding very few that necessitate 16-bit processing. Ross concludes that while 16-bit can enhance color depth, the perceptible difference to the average viewer is minimal, and the choice between 8-bit and 16-bit should be based on the specific needs of the project and the摄影师's equipment capabilities.

Keywords

💡Bit-depth

Bit-depth refers to the number of bits used to represent the color or tone of a single pixel in an image. In the video, it is explained as the range of tonal values from absolute black to absolute white, with 8-bit being the standard for most digital media. The video emphasizes the importance of bit-depth in determining the quality and smoothness of an image, particularly when dealing with gradients and subtle color changes. Higher bit-depths, such as 16-bit, allow for a greater number of color variations, leading to smoother gradients and less visible banding in images.

💡Tonal range

Tonal range is the spectrum of colors or shades of gray that an image can display, from the darkest black to the brightest white. The video discusses how understanding tonal range is crucial for image editing, as it affects the image's overall appearance and quality. The script mentions absolute black (100 black), three-quarter tones (75 gray), mid-tones (50 gray), quarter tones (25 gray), and absolute white (0 percent) as key points in the tonal range, which are essential for achieving a balanced and detailed image.

💡RGB

RGB stands for Red, Green, and Blue, which are the primary colors used in digital imaging to create a wide array of colors. In the video, the concept of RGB is used to explain how each color channel contributes to the overall color and luminance of an image. The video mentions that each color channel in an 8-bit image has 256 levels of gray, resulting in a total of 16.7 million colors when combined. This concept is fundamental to understanding how digital images are constructed and how they can be manipulated for various outputs.

💡Pixel

A pixel is the smallest unit of an image, essentially a single point of color or light. The video describes a pixel as a data point containing information about color and luminance, with the accuracy of this information being determined by the bit-depth. The script uses the pixel as a foundational concept to explain how images are made up and how the manipulation of pixel data can affect the final appearance of an image.

💡8-bit

8-bit is a standard color depth used in digital imaging, where each color channel (red, green, and blue) has 256 levels of intensity, resulting in 16.7 million possible colors. The video discusses 8-bit as being sufficient for most digital media and regular photography, but it also points out its limitations when compared to higher bit-depths, such as 16-bit. The script uses 8-bit as a reference point to illustrate the differences in image quality and editing capabilities between various bit-depths.

💡16-bit

16-bit is a higher color depth than 8-bit, offering 65,536 levels of intensity per color channel, which results in 281 trillion possible colors. The video highlights 16-bit as a preferred option for professionals, particularly in beauty and fashion retouching, due to its ability to handle a greater amount of color data and provide smoother gradients. The script contrasts 16-bit with 8-bit to demonstrate how higher bit-depths can prevent banding and offer more flexibility in image editing.

💡Banding

Banding refers to the visible lines or steps in an image where there is a sudden change in color or tone. The video explains that banding occurs when there are not enough color steps to smoothly transition between shades, which is more likely to happen in 8-bit images. The script uses banding as an example of a problem that can be mitigated by using higher bit-depths, such as 16-bit, which provide more color steps and smoother tonal transitions.

💡Raw files

Raw files are a type of image file format that contains minimally processed data from the image sensor of a digital camera. The video mentions that professionals often work with raw files to utilize the extra color information they contain, which is typically captured in higher bit-depths like 12-bit. The script suggests that working with raw files at higher bit-depths can provide more flexibility and detail in post-processing.

💡32-bit

32-bit is an extremely high color depth that is used primarily for creating High Dynamic Range (HDR) images. The video cautions that while 32-bit offers a vast color range, it requires reducing the bit-depth for most practical uses, which can distort colors and tones. The script briefly touches on 32-bit as a specialized domain within digital imaging, suggesting that it is not typically necessary for standard image editing workflows.

💡HDR

HDR stands for High Dynamic Range and refers to techniques used in photography and imaging to capture a greater range of luminosity and detail than standard methods. The video mentions HDR in the context of 32-bit color depth, indicating that HDR is an area where the full capabilities of 32-bit processing can be utilized. The script implies that HDR is a specialized application where the benefits of higher bit-depths become more apparent.

Highlights

Understanding bit-depth is crucial for managing an image's tonal range, which affects both screen and print quality.

Tonal range in images is the spectrum from absolute black to absolute white, with various shades of gray in between.

Each shade of tone in a grayscale image is referred to as a step, indicating the number of transitions from black to white.

Color images use RGB channels, where darker shades represent higher concentrations of color.

Pixels are data points containing color and luminance information, with accuracy determined by bit depth.

Photoshop defaults to 8-bit images, suitable for web and digital media but limiting for color data.

8-bit RGB offers 256 levels per channel, totaling 16.7 million colors, which is often sufficient for regular photography.

Professionals use 10-bit or higher displays and graphics cards to access more color data from RAW files.

Digital cameras often capture in 12-bit mode, offering 68.71 billion colors,远超8-bit capabilities.

16-bit mode in Photoshop supports 2.81 trillion colors, beneficial for beauty and fashion retouchers.

Higher bit depths reduce the potential for banding in tones, providing smoother gradients.

16-bit images can handle more aggressive editing without losing tonal quality compared to 8-bit images.

32-bit images are used for creating HDR images, but are not practical for everyday use in Photoshop due to limited feature access.

Most images can be adequately displayed and printed using 8-bit, but 16-bit can eliminate banding concerns.

The presenter's experience suggests that 16-bit is not always necessary, despite the benefits it provides over 8-bit.

High-resolution cameras may not benefit significantly from 16-bit due to workflow slowdowns in Photoshop.

The true value of 16-bit depth may be limited by the inability of monitors and printers to fully utilize its color range.

The decision between 8-bit and 16-bit should be based on the specific needs of the image and the intended presentation medium.

Transcripts

[Music]

my name is john ross from the art of

retouching studio in this video we're

going to be talking about how the bit

depth of an image affects the tonal

range of an image this is important to

understand because if you allow

photoshop to be in control it will

easily choose something for screen

display and not necessarily for print

display

tonal range goes from absolute black to

absolute white with shades of gray in

between

absolute black is referred to as 100

black

inside of the shadow areas it's referred

to as 75 gray or the three quarter tones

next we have 50 gray or the mid tones

and then we have 25 percent gray

otherwise known as the quarter tones and

finally zero percent which is absolute

white at its core this information is

good for simple grayscale images where

you have black white and shades of gray

in between each shade of tone is

referred to as a step because as you

will soon see you are only allowed a

certain amount of steps when going from

black to white

once you introduce the concept of color

you can now work in rgb which is red

green and blue

each color gets its own channel it kind

of looks like the old film days

here we have the darker the shade the

higher concentration of that color if

you were to overlay each of the channels

together they combine to display a full

color image your images are made up of

pixels think of a pixel as a single data

point that contains information about

color and luminance the accuracy of the

information is determined by the bit

depth of that data bit depth is the

number of steps or shades of gray that

it takes to go from absolute black to

absolute white photoshop by default

wants to work on your images as 8-bit

this is fine for websites and other

digital media this is also good because

most devices use an 8-bit display while

you could easily get away with using

8-bit for your regular photography

images as you will see you will actually

be missing out on a lot of possible

color data this is because 8-bit is

actually quite limiting but in general

most people are working in 8-bit rgb the

bit depth allows for 256 discrete levels

of information per pixel per channel

this means that you will have 256 steps

of gray for the red channel 256 steps of

gray for the blue channel and 256 steps

of gray for the green channel once they

all get combined together that becomes

256 times 256 times 256 which equals

16.7 million colors now that sounds like

a lot of colors and in most cases it

works out just fine

however there is much more information

that can be had when working with your

raw files

to utilize the extra information

professionals spend more money on

monitor and graphics cards where one of

the perks gives them a 10-bit display

this is

1.07 billion colors this sounds great

but your digital camera is likely to be

capturing in 12-bit mode which is even

higher at

68.71 billion colors suddenly working in

only 8-bit with 16.7 million colors

sounds kind of small

that's because it is and we still have a

lot more to go if you were to look

inside of photoshop image mode you can

see that there are three options 8-bit

16-bit and 32-bit

beauty and fashion retouchers will often

use that 16-bit option because that

supports 2.81 trillion colors

conceptually you need that because once

you bring your 12-bit image into

photoshop at 16-bit you are then allowed

the freedom to grow once you start

adding adjustment layers like levels and

curves the higher the bits the more the

steps and the less potential there is

for banding in the tones

we have the same gradation in both the

top image and the bottom image the

difference here is that the top image is

an 8-bit and the lower image is 16-bit

currently they both look the same

i'm going to start with the 8-bit image

by using the levels adjustment i'm going

to change the black output levels to be

110 and the white output level to be

148. this simple move turned the

gradient into an almost solid gray

what i just did was modify the absolute

black tones and the absolute white tones

and photoshop crushed that information

into this narrow band for the tonal

range if i was to take that level that i

just made and drop it onto the 16-bit

image below then visually it does the

exact same thing

now here's where things start getting

funky if i create a new levels

adjustment and on the top area i change

black to 110 and the white to 148 you

will see that the 16 bit image is back

to where it was when we first started a

nice smooth gradient from absolute black

to absolute white if i take the levels

adjustment layer that i just created and

i drag that onto the 8-bit image your

mind should now be blown because we now

have a huge difference between the two

where this 8-bit image is completely

banding and it looks nothing like it did

in the beginning however the 16-bit

image looks the same as it did in the

beginning

the 16-bit version has enough overhead

that it can handle being torn apart and

put back together again

that is the difference between 8-bit and

16-bit once again if you only have 256

shades of gray per channel in 8 bit it

means that when you start dealing with

16 bit depth you now have 65 000 shades

of gray per channel when that computer

has to choose from in order to rebuild

the missing data this was a very

deliberate and very technical example in

the real world images are going to look

the same to us to the computer however

it has a wider range of possible colors

to choose from this means any

possibility of banding like you see here

can be avoided

let's get into a real world example with

this image here there are a lot of

different things going on you have blues

you have oranges you have black you have

tones that are bright and dark different

things are happening and it's all broken

up using 8-bit which utilizes 16.7

million colors is more than enough to

display this image and print this image

moving on things are going to get more

complex

in order to see what i'm talking about i

need to zoom in about 800 percent here

is a sunset in eight bit well generally

it looks fine

now let's compare that same image to a

16-bit version

when comparing you can actually see how

the 8-bit image is a bit more blotchy

and choppy at 16 bit it's much softer

not because it's blurry but because it

has 64 times more colors to work with so

it can give a smoother transition from

one pixel to the next if we introduce

the 32-bit version it's most obvious in

the top orange areas we can see that

when looking at all three together the

higher the bit rate the more colors it

has to choose from but

32-bit is tricky because in order to

actually use this file we need to drop

the bit depth down and then that

distorts the colors and tones in

unpredictable ways additionally once you

enable 32-bit photoshop actually breaks

with less than half of the features

still working

most things are simply grayed out or

inaccessible in order to really start

showing you what i mean i've

intentionally boosted the contrast of

these next images the 8-bit once again

looks fine but that's only until we

compare it to the 16-bit version once

again when you get up close you can see

how crisp and crunchy those pixels are

in 8-bit because they can't make the

softer transitions in this last example

you can see how 8-bit has really severe

hard pixelization and distinct banding

banding is when you clearly see the

rings or the lines it's the steps we

were talking about earlier as it tries

to go from one shade to the next it

isn't as noticeable in the 16-bit

version because it can make those

smoother transitions

if you're in the dark about as to

whether or not you need to use 8-bit or

16-bit for your image unless you have a

severe sunset gradient you are more than

likely okay with 8-bit if you feel as

though you may have a problem simply

change 8-bit to 16-bit while you're

still editing in lightroom or camera raw

before exporting the file if you do that

you should expect a nice smooth gradient

out of your image

but yeah this is the reason why high-end

photographers and retouchers use 16 bits

per channel as a standard it doesn't

mean that every image actually needs it

very few actually do however we no

longer need to even worry about banding

as a topic for us or for our clients

after photoshop's image modes 16 bits

per channel this is followed by

photoshop's image mode 32 bits per

channel 32-bit however is a whole other

beast it is the exclusive domain when

creating hdr images no need to even

think about this bit depth again inside

of photoshop

so always keep your images at 16 bit and

you'll be glad that you did

however here's the thing though in

working on this video i had the hardest

time coming up with any images that

actually required 16 bit as a

professional it's my job to say that you

need to use 16 bit on every image

however as a professional i also know

where the color increase and more

importantly the size increase is

actually needed the problem we are

dealing with today is that the new

cameras come with such high megapixels

generally between 40 and 100

that working on them in 16 bit isn't

really worth the slowed down workflow in

photoshop

i have a beast of a machine and yet

using 16-bit with smart objects from a

50-megapixel camera really leaves me

waiting around while it pushes all those

colors don't mistake the difference of

using 16-bit versus 8-bit will reveal an

entirely new world of color it really

just adds greater depth of possibility

to each pixel of data the thing is your

monitor can't see it and your printer

can't print it so other than the placebo

effect is there any true value in 16-bit

depth sunset images have massive

gradations of similar hues

quite often an 8-bit display will not be

able to show every color variant within

that gradation instead it will replace

the color with the nearest neighbor that

it can display this will lead to visual

banding on your monitor

i went through my own catalog of 90 000

images and then i went through a

professional photographer's catalog of

500 000 images and i was only able to

come up with a small handful i would

even consider 16 bit as mandatory

pros will likely disagree with me but i

stand my ground

the reason is that while all images will

benefit from 16-bit over 8-bit obviously

the true test is in the presentation

assuming most digital displays are 8-bit

the quality will automatically be

downgraded anyway also considering print

media needs to go through an 8-bit cmyk

conversion i further stand my ground

for the passionate i get it if you have

two adjacent pixels of similar quality

in 16-bit we will certainly have two

adjacent pixels that are completely

different in 8-bit we will obviously

lose fidelity of color tone variation

and definition but i sustain that normal

people glancing at the image simply

couldn't care less either you agree or

disagree with my assessment of 8-bit

versus 16-bit images leave your comments

below and that leads us to our next

major topic resolution be sure to check

out that video as well the link is in

the description below

if you found this video helpful please

go to

www.theartofretouching.com where you can

find more tips and tricks to make you a

better photo retoucher

[Music]

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