Graphic images are normally not continuous tone (gradients are possible in graphics, but are seen less often). Graphics are drawings, not photos, and they use relatively few colors, maybe only two or three, often less than 16 colors in the entire image. In a color graphic cartoon, the entire sky will be only one shade of blue where a photo might have dozens of shades. A map for example is graphics, maybe 4 or 5 map colors plus 2 or 3 colors of text, plus blue water and white paper, often less than 16 colors overall. These few colors are well suited for Indexed Color, which can re-purify the colors. Don’t cut your color count too short though – there will be more colors than you count. Every edge between two solid colors likely has maybe six shades of anti-aliasing smoothing the jaggies (examine it at maybe 500% size). Insufficient colors can rough up the edges. Scanners have three modes to create the image: color (for all color work), grayscale (like B&W photos), and lineart. Line art is a special case, only two colors (black or white, with no gray), for example clip art, fax, and of course text. Low resolution line art (like cartoons on the web) is often better as grayscale, to add anti-aliasing to hide the jaggies.
If it’s a scan of a black & white image you probably want to go with TIFF or PNG.
Something we all need to know, but it takes more to show this, so it was placed on its own page.
For example, say you have taken a photo of a red and blue flower.
Also note the software used to convert images to JPEG can make major differences. Photoshop, for instance, can explicitly operate in greyscale mode so that when you save there’s no sneaky color artifacts wasting space. GIMP and xnview also do a good job and offer lots of options for tuning JPEGs.
Now imagine that you have a straight from camera color jpeg of the same scene. You have more information. You can perform global adjustments on the image that will affect the red flower and the blue flower differently. By applying a red filter you will darken the blue flower (by reducing the blue saturation) without darkening the red flower. Then when you convert to B&W the red flower will be a lighter shade of gray than the blue flower.
We all have our own notions, but here is a popular opinion about the ultimate, in quality, in versatility, in convenience. RAW files are popular indeed, from most DSLR cameras. When we take any digital picture, the camera has a RAW sensor, but normally processes and outputs the image as a JPG file. But often we can choose to output the original RAW image instead, to defer that JPG step until later. We cannot view or use that RAW file any way other than to process it in computer software and then output a final TIF or JPG image, however postponing this processing offers a few serious advantages, better editing options, and we can bypass all JPG artifacts entirely, until the one final output Save for whatever purpose. RAW allows us to tweak exposure and color, and defer White Balance decisions until later when we can see the image first, and judge any trial results. The 12-bit RAW file offers greater range for any of our adjustments, often on multiple files simultaneously. And RAW always preserves the intact original version, so we can easily back out any editing changes we made, crop size for example. An argument is made that processing RAW requires this extra step, but of course, same is true of any editing that is required. RAW is the easy way, with the best results.
Imagine that the straight from camera B&W jpeg rendered both flowers in the exact same shade of gray. You can no longer see any difference between the tonal value of the red flower and the tonal value of the blue flower. Whatever global adjustments you make to the image will equally affect both flowers the same. The information regarding the different color of the two flowers has been irrevocably discarded.
Finally, imagine that you are working with the raw data from the camera. You have even more information than that contained in the color jpeg. In fact, you have so much information that your 24-bit monitor (8-bits per color channel) can’t even display it all at the same time. What you see on your screen isn’t all of the raw data from the file. Rather it is a demosaiced conversion to 8-bits per channel that is displayed on your screen. When you use certain sliders or settings the entire raw data is used to alter the conversion reduced to 8-bits that you see on your screen. All of the information collected by the sensor is still at your disposal. As long as you retain the raw file, you retain all of that information. Your editing is saved non-destructively as a set of instructions on what to do with that information.
We hear: But RAW images require an editing step first. Some people do seem terrified of the word “edit”, but no matter what, we do always have to stop and look at our images on the computer, every one of them. That is the same extra step. Surely we have to crop them a bit, and resample smaller, and many of mine will need a slight Exposure or White Balance tweak to be their best. It makes a tremendous difference. That is the same editing, a few seconds each, a few clicks, and then the file must be saved again. You might as well do this step in the RAW software, which has better easier tools to do it, and more range to do it., and of course, we can SEE the image now. If your session included 100 images of same lighting situation, just select them all, edit ONE of them (say White Balance and Exposure, even Cropping, etc), and the same edit clicks are applied to all of the selected RAW images in one click. Extremely convenient. And no JPG artifacts of course, no losses, and any changes can easily be Undone anytime later, with full recovery of our original RAW master copy. RAW is the trivial, easy, and good way, Day and Night good, if you care about these things.
Always uses lossy JPG compression, but its degree is selectable, for higher quality and larger files, or lower quality and smaller files. JPG is for photo images, and is the worst choice for most graphics or text data.
An additional note. If you are editing your photo using Photoshop, keep your working files in Photoshop, masks, layers. And again, export to JPEG.
2) Working files (PSD, Gimp file, the recipe of the photo in lightroom)
PNG files are lossless and, if you can afford the space they consume, are the best option.
Supports transparency in regular indexed color, and also there can be a fourth channel (called Alpha) which can map RGB graduated transparency (by pixel location, instead of only one color, and graduated, instead of only on or off).
JPG files are very small files for continuous tone photo images, but JPG is poor for graphics, without a high Quality setting. JPG requires 24-bit color or 8-bit grayscale, and the JPG artifacts are most noticeable in the hard edges of graphics or text. GIF files (and other indexed color files) are good for graphics, but are poor for photos (too few colors possible). However, graphics are normally not many colors anyway. Formats like TIF and PNG can be used either way, 24-bit or indexed color – these file types have different internal modes to accommodate either type optimally. Basics
I’m slightly confused by what you mean by “In which file format should I save black and white photographs?”.
To retain the most information and have the most flexibility when working with the file in post processing save your image in your camera’s raw file format as you shoot them.
Our digital images are dimensioned in pixels (not bytes, and definitely not inches). And a pixel is simply a color definition, the color that this tiny dot of image sampled area ought to be. Put all those colored dots together, and our brain sees the image. The losses of image data we are speaking about is about the altered color of the pixels.
Image data consists of pixels, and pixels are “colors”, simply the storage of the three RGB data components (see What is a Digital Image Anyway?).
PNG uses ZIP compression which is lossless, and somewhat more effective color compression than GIF or TIF LZW. For photo data, PNG is somewhat smaller files than TIF LZW, but larger files than JPG (however PNG is lossless, and JPG is not.) PNG is a newer format than the others, designed to be both versatile and royalty free, back when the patent for LZW compression was disputed for GIF and TIF files.
The APNG version also supports animation (like GIF), showing several sequential frames fast to simulate motion.
If you or the person helping you has Adobe software available, then I disagree with Seal’s recommended adjustments, especially for the type of artwork you have where black is black and white is white. If the interior is a PDF/X-1a file with the images defined in DeviceGray colorspace, then it will print as expected. The digital presses used for b&w print-on-demand interiors fuse ink to the surface of the paper — it is not absorbed into the grain as with traditional offset printing. (If the paper is stored and handled properly prior to printing, then any changes in darkness/lightness should be minimal once the finished book cools, and would mostly be caused by the scuffing or buffing that occurs when between facing pages — and even those changes are not usually noticeable unless there are very heavy ink coverages. Of course, we do sometimes receive books where the paper wasn’t handled properly or equipment was overdue for maintenance, but you can’t plan on things like that when preparing the print-ready PDF — those kinds of problems are what the CreateSpace guarantee is for.)
One color in indexed color can be marked transparent, allowing underlaying background to be seen (very important for text, for example). GIF is an online video image, the file contains no dpi information for printing. Designed by CompuServe for online images in the days of dialup and 8-bit indexed computer video, whereas other file formats can be 24-bits now. However, GIF is still great for web use of graphics containing only a few colors, when it is a small lossless file, much smaller and better than JPG for this. GIF files do not save the dpi number for printing resolution.
But you are still limited to only modifying the information that was contained in the color jpeg. Some information from the sensor contained in the raw data was discarded in the process of producing the jpeg in the camera and that information is not recoverable from the color jpeg any more than the difference between blue and red was not recoverable from the B&W jpeg that showed them as the exact same shade of grey!
2,858 Views 7 Replies Last post: Jul 3, 2014 2:40 PM by Lighthouse24
Versatile, many formats supported. Mode: RGB or CMYK or LAB, and others, almost anything. 8 or 16-bits per color channel, called 8 or 16-bit “color” (24 or 48-bit RGB files). Grayscale – 8 or 16-bits, Indexed color – 1 to 8-bits, Line Art (bilevel)- 1-bit
In what format are the source images? If they’re 1-bit black-and-white line art (and they look like they could be), then I’d leave them that way and save them for page insertion as TIF images in B&W mode (with a resolution of at least 600 pixels per inch). If they were scanned in as color or 8-bit grayscale images, then they may not convert well to 1-bit line art (but I would try that first), and if they don’t, then I would save them as 8-bit grayscale at 300 pixels per inch. So long as file size is not an issue, I would still use TIF for that. But if you have a lot of images and file size is a concern, then JPG with highest quality minimum compression.
If you mean an image from a camera, then it’s /not/ black and white, but colour, and you should, as already expressed, save it in RAW. But I’m concerned with why you would have called it a b&w image. Because you wish to /target/ a final b&w image by post processing, or because you are converting in-camera. If the later then you’re probably not going to start doing work in post and so RAW is useless to you at this stage.
Note that if your image size is say 3000×2000 pixels, then this is 3000×2000 = 6 million pixels (6 megapixels). Assuming this 6 megapixel image data is RGB color and 24-bits (or 3 bytes per pixel of RGB color information), then the size of this image data is 6 million x 3 bytes RGB = 18 million bytes. That is simply how large your image data is (see more). Then file compression like JPG or LZW can make the file smaller, but when you open the image in computer memory for use, the JPG may not still have the same image quality, but it is always still 3000×2000 pixels and 18 million bytes. This is simply how large your 6 megapixel RGB image data is (megapixels x 3 bytes per pixel).
Always grayscale if you are going b&w. Also brighten and enhance contrast by 25%/15% respectively as ink bleeds into the paper as it dries and you don’t want your images to become muddy because you are adding too much ink. They should look too bright on the computer monitor, but not washed out.
Photo images have continuous tones, meaning that adjacent pixels often have very similar colors, for example, a blue sky might have many shades of blue in it. Normally this is 24-bit RGB color, or 8-bit grayscale, and a typical color photo may contain perhaps a hundred thousand RGB colors, out of the possible set of 16 million colors in 24-bit RGB color.
In which file format should I shoot black and white photographs?
Image size (pixels) determines how we can use the image – everything is about the pixels. See a summary of digital basics.
When you have all of that original information you have much more latitude with what you can do in post processing than if you had only saved a post-demosaiced image from the camera after it did the demosaicing itself based on the in-camera settings at the time. You can change a setting or move a slider and your post processing application will redo the demosaicing to apply the changes you have made to the original data collected by the sensor rather than applying it to the more limited information contained in a jpeg produced in camera.
Just remember, everything in a raw file is a monochromatic luminance value. With a conventional Bayer mask half the pixels are filtered to be most responsive to green light, and one quarter are filtered to be most responsive to either red or blue light. But some red and some blue light does make it through the green filter, and some green light makes it through both the red filters and the blue filters. Very little to no blue light makes it through the red filters and vice versa. There is no real color information in a raw file. Only by demosaicing that information and knowing which color filter each pixel was filtered for can color information be interpolated from the raw data.
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GIF also supports animation, showing several sequential frames fast to simulate motion.
Camera RAW files is one way to bypass this JPG issue, at least until the last one final save as JPG when required. And it offers additional processing advantages too. Better easier tools in RAW than JPG has, the RAW data has wider range than JPG has. Much the same controls as in the camera, which you would have needed anyway, but this step is done after you see the camera results, to know exactly what it still needs, and can simply tweak and judge it by eye (as opposed to settings in the camera done in advance, as hopeful wishing).
For print it can be on TIFF. And you could export at grayscale at 16 bits. But that is only for specialized usage. For most users, JPEG is fine.
Jul 3, 2014 11:24 AM What format for black & white graphic images?
JPEG has been going strong as the best quality-size tradeoff for a long time. Google is working on their WebP image format, which is said to not perform all that better than JPEG.
Indexed color – 1 to 8-bits (8-bit indexes, limiting to only 256 colors maximum.) Color is 24-bit color, but only 256 colors.
3) Output files (JPEG, some resampled photos to upload to some website, TIFF files to be printed professionally, the new JPEG file you converted to grayscale from the original color photo, etc.)
Everything I found on the internet was about black and white image scans and general image file formats.
PNG and TIF LZW are lossless compression, so their file size reduction is not as extreme as the wild heroics JPG can dream up. In general, selecting lower JPG Quality gives a smaller worse file, higher JPG Quality gives a larger better file. Your 12 megapixel RGB image data is three bytes per pixel, or 36 million bytes. That is simply how big your image data is. Your JPG file size might only be only 5-20% of that, literally. TIF LZW might be 65-80%, and PNG might be 50-65% (very rough ballpark for 24-bit color images). We cannot predict sizes precisely because compression always varies with image detail. Blank areas, like sky and walls, compress much smaller than extremely detailed areas like a tree full of leaves. But the JPG file can be much smaller, because JPG is not required to recover the original image intact, losses are acceptable. Whereas, the only goal of PNG and TIF LZW is to be 100% lossless, which means the file is not as heroically small, but there is never any concern about compression quality with PNG or TIF LZW. They still do impressive amounts of file size compression, remember, the RGB image data is actually three bytes per pixel.
As others are saying, avoid discarding the RAW files “.CR2” for most Canon cameras. Those raw files contain data that has to be interpreted by software and the image could look completely different if you’re opening it with Photoshop vs the default image viewer on your PC. Once you enter the realm of processed images, you now have a set of pixels on your screen that you want to save for yourself or others and when it gets reopened it’s as close to the original as possible.
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All photo editor programs will support these file formats, which will generally support and store images in the following color modes:
But, as you you asking the question at all you should certainly look at saving in RAW and doing your b&w conversions in post, using the colour in the image to help you achieve a more impressive final result. iirc Nix’s Silver Efex is now free.
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The most common image file formats, the most important for general purposes today, are JPG, TIF, PNG and GIF. These are not the only choices of course, but they are good and reasonable choices for general purposes. Newer formats like JPG2000 never acquired popular usage, and are not supported by web browsers, and so are not the most compatible choice.
For TIF files, most programs allow either no compression or LZW compression (LZW is lossless, but is less effective for color images). Adobe Photoshop also provides JPG or ZIP compression in TIF files too (but which greatly reduces third party compatibility of TIF files). “Document programs” allow ITCC G3 or G4 compression for 1-bit text (Fax is G3 or G4 TIF files), which is lossless and tremendously effective (small). Many specialized image file types (like camera RAW files) are TIF file format, but using special proprietary data tags.
Might I also appeal for you to not fall into the trap of using color filters on camera as you would with b&w film stock? A strong red filter, for instance, will lose 75% of the resolution of your sensor due to the way the Bayer sensor works.
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If you send me one of the 8-bit grayscale images you’re working with (and a 1-bit version of the same image, if desired), I’ll be happy to take a look, tell you what you can expect, and suggest whether or not I think additional adjustments would be needed.
The Next button will browse through the descriptions on the next pages, or you can use these shortcut links directly: JPG Format PNG Format TIF Format GIF Format
Shoot in RAW, and export on whatever format you like. JPEG for example.
So – for example- any 10 megapixel camera image data will occupy 3×10 = 30 million bytes, by definition of RGB color. This number is the “data size” (when opened into computer memory for use). A TIF file will be near that size (and is lossless), but JPG is normally compressed very heavily (lossy, not lossless) to store in a JPG file of perhaps 1/10 this size (variable with JPG Quality setting), which is “file size” (not image size and not data size). This example image size is still 10 megapixels (dimensioned in pixels, width x height), and the data size is 30 million bytes, but the JPG file size might be 3 MB (lossy compression takes a few liberties). The image will still come out of the JPG file as the same 10 megapixels and the same 30 million bytes when the 3 MB JPG file is opened. We hope its quality also comes out about the same – the JPG losses are altered color values of some of the pixels).
1) Original Files (RAW, or your original JPEG from the camera)
24-bits is called 8-bit color, three 8-bit bytes for RGB (256x256x256 = 16.7 million colors maximum.) Or 48-bits is called 16-bit color, three 16-bit words (65536x65536x65536 = trillions of colors conceptually)
GIF uses lossless LZW compression. (for Indexed Color, see second page at GIF link at page bottom).
24-bit images contain 256 shades of gray and so a 256 color GIF will also be lossless, however it is less efficient than PNG and will result in larger file sizes with no gain other than compatibility with ancient computers.
Someone is helping me clean-up and prepare my images for POD on both createspace and Ingramspark. These are black and white calligraphy graphics for a black and white interior. What is the best way to save the images? Grayscale? Bitmap? RGB? and should they best be saved as PNG? JPEG? TIFF? or what? I don’t see where to include an image in this post so I’ve provided links to sample images below. Thank you for your help.
RGB – 24 or 48-bits (called 8-bit or 16-bit “color”), Alpha channel for RGB transparency – 32 bits Grayscale – 8 or 16-bits, Indexed color – 1 to 8-bits, Line Art (bilevel) – 1-bit
Any 24-bit RGB image will use three bytes per pixel (see Color Bit-Depth – Memory Size).