Digital Image File Types
Originaly posted by Gerbe Dumahil (sketchup-vray artists)
Digital Image File Types Explained
JPG, GIF, TIFF, PNG, BMP. What are they, and how do you choose? These and many other file types are used to encode digital images. The choices are simpler than you might think.
Part of the reason for the plethora of file types is the need for compression. Image files can be quite large, and larger file types mean more disk usage and slower downloads. Compression is a term used to describe ways of cutting the size of the file. Compression schemes can by lossy or lossless.
Another reason for the many file types is that images differ in the number of colors they contain. If an image has few colors, a file type can be designed to exploit this as a way of reducing file size.
Lossy vs. Lossless compression
You will often hear the terms "lossy" and "lossless" compression. A lossless compression algorithm discards no information. It looks for more efficient ways to represent an image, while making no compromises in accuracy. In contrast, lossy algorithms accept some degradation in the image in order to achieve smaller file size.
A lossless algorithm might, for example, look for a recurring pattern in the file, and replace each occurrence with a short abbreviation, thereby cutting the file size. In contrast, a lossy algorithm might store color information at a lower resolution than the image itself, since the eye is not so sensitive to changes in color of a small distance.
Number of colors
Images start with differing numbers of colors in them. The simplest images may contain only two colors, such as black and white, and will need only 1 bit to represent each pixel. Many early PC video cards would support only 16 fixed colors. Later cards would display 256 simultaneously, any of which could be chosen from a pool of 224, or 16 million colors. New cards devote 24 bits to each pixel, and are therefore capable of displaying 224, or 16 million colors without restriction. A few display even more. Since the eye has trouble distinguishing between similar colors, 24 bit or 16 million colors is often called TrueColor.
The file types
TIFF is, in principle, a very flexible format that can be lossless or lossy. The details of the image storage algorithm are included as part of the file. In practice, TIFF is used almost exclusively as a lossless image storage format that uses no compression at all. Most graphics programs that use TIFF do not compression. Consequently, file sizes are quite big. (Sometimes a lossless compression algorithm called LZW is used, but it is not universally supported.)
PNG is also a lossless storage format. However, in contrast with common TIFF usage, it looks for patterns in the image that it can use to compress file size. The compression is exactly reversible, so the image is recovered exactly.
GIF creates a table of up to 256 colors from a pool of 16 million. If the image has fewer than 256 colors, GIF can render the image exactly. When the image contains many colors, software that creates the GIF uses any of several algorithms to approximate the colors in the image with the limited palette of 256 colors available. Better algorithms search the image to find an optimum set of 256 colors. Sometimes GIF uses the nearest color to represent each pixel, and sometimes it uses "error diffusion" to adjust the color of nearby pixels to correct for the error in each pixel.
GIF achieves compression in two ways. First, it reduces the number of colors of color-rich images, thereby reducing the number of bits needed per pixel, as just described. Second, it replaces commonly occurring patterns (especially large areas of uniform color) with a short abbreviation: instead of storing "white, white, white, white, white," it stores "5 white."
Thus, GIF is "lossless" only for images with 256 colors or less. For a rich, true color image, GIF may "lose" 99.998% of the colors.
JPG is optimized for photographs and similar continuous tone images that contain many, many colors. It can achieve astounding compression ratios even while maintaining very high image quality. GIF compression is unkind to such images. JPG works by analyzing images and discarding kinds of information that the eye is least likely to notice. It stores information as 24 bit color. Important: the degree of compression of JPG is adjustable. At moderate compression levels of photographic images, it is very difficult for the eye to discern any difference from the original, even at extreme magnification. Compression factors of more than 20 are often quite acceptable. Better graphics programs, such as Paint Shop Pro and Photoshop, allow you to view the image quality and file size as a function of compression level, so that you can conveniently choose the balance between quality and file size.
RAW is an image output option available on some digital cameras. Though lossless, it is a factor of three of four smaller than TIFF files of the same image. The disadvantage is that there is a different RAW format for each manufacturer, and so you may have to use the manufacturer's software to view the images. (Some graphics applications can read some manufacturer's RAW formats.)
BMP is an uncompressed proprietary format invented by Microsoft. There is really no reason to ever use this format.
PSD, PSP, etc. , are proprietary formats used by graphics programs. Photoshop's files have the PSD extension, while Paint Shop Pro files use PSP. These are the preferred working formats as you edit images in the software, because only the proprietary formats retain all the editing power of the programs. These packages use layers, for example, to build complex images, and layer information may be lost in the nonproprietary formats such as TIFF and JPG. However, be sure to save your end result as a standard TIFF or JPG, or you may not be able to view it in a few years when your software has changed.
Currently, GIF and JPG are the formats used for nearly all web images. PNG is supported by most of the latest generation browsers. TIFF is not widely supported by web browsers, and should be avoided for web use. PNG does everything GIF does, and better, so expect to see PNG replace GIF in the future. PNG will not replace JPG, since JPG is capable of much greater compression of photographic images, even when set for quite minimal loss of quality.
When should you use each?
This is usually the best quality output from a digital camera. Digital cameras often offer around three JPG quality settings plus TIFF. Since JPG always means at least some loss of quality, TIFF means better quality. However, the file size is huge compared to even the best JPG setting, and the advantages may not be noticeable.
A more important use of TIFF is as the working storage format as you edit and manipulate digital images. You do not want to go through several load, edit, save cycles with JPG storage, as the degradation accumulates with each new save. One or two JPG saves at high quality may not be noticeable, but the tenth certainly will be. TIFF is lossless, so there is no degradation associated with saving a TIFF file.
Do NOT use TIFF for web images. They produce big files, and more importantly, most web browsers will not display TIFFs.
This is the format of choice for nearly all photographs on the web. You can achieve excellent quality even at rather high compression settings. I also use JPG as the ultimate format for all my digital photographs. If I edit a photo, I will use my software's proprietary format until finished, and then save the result as a JPG.
Digital cameras save in a JPG format by default. Switching to TIFF or RAW improves quality in principle, but the difference is difficult to see. Shooting in TIFF has two disadvantages compared to JPG: fewer photos per memory card, and a longer wait between photographs as the image transfers to the card. I rarely shoot in TIFF mode.
Never use JPG for line art. On images such as these with areas of uniform color with sharp edges, JPG does a poor job. These are tasks for which GIF and PNG are well suited.
If your image has fewer than 256 colors and contains large areas of uniform color, GIF is your choice. The files will be small yet perfect.
PNG is of principal value in two applications:
- If you have an image with large areas of exactly uniform color, but contains more than 256 colors, PNG is your choice. Its strategy is similar to that of GIF, but it supports 16 million colors, not just 256.
- If you want to display a photograph exactly without loss on the web, PNG is your choice. Later generation web browsers support PNG, and PNG is the only lossless format that web browsers support.
PNG is superior to GIF. It produces smaller files and allows more colors. PNG also supports partial transparency. Partial transparency can be used for many useful purposes, such as fades and antialiasing of text. Unfortunately, Microsoft's Internet Explorer does not properly support PNG transparency, so for now web authors must avoid using transparency in PNG images.
When using graphics software such as Photoshop or Paint Shop Pro, working files should be in the proprietary format of the software. Save final results in TIFF, PNG, or JPG.
Use RAW only for in-camera storage, and copy or convert to TIFF, PNG, or JPG as soon as you transfer to your PC. You do not want your image archives to be in a proprietary format. Although several graphics programs can now read the RAW format for many digital cameras, it is unwise to rely on any proprietary format for long term storage. Will you be able to read a RAW file in five years? In twenty? JPG is the format most likely to be readable in 50 years.Thus, it is appropriate to use RAW to store images in the camera and perhaps for temporary lossless storage on your PC, but be sure to create a TIFF, or better still a PNG or JPG, for archival storage.
Tips and Tricks to Speed UP your Rendering
Tips and Tricks on how to speed up rendering for 3d models
1.) as much as possible limit ur polycount to minimum.
the more poly the slower the rendering.
2.) if ur using vray, always proxy the ones with high polycount.
3.) don't put too much subdivisions on your shadows (as much as possible).
4.) remove unwanted object on your scene
5.) dont use so giant/ultra/high texture if your rendering small output
try to proportion both.
6.) material wise: avoid using too much glossiness and highlights, a simple diffuse, bump and reflection(with .95 - .75) will do.. try not to use archshaders..
7.) use high polys object only when the object is very near to the view or camera
8.) for exterior: standard directlight(as ur sun) and vray environment light is much more faster to render compared to vraysun and sky.. u just need to tweak the colors to achieved the sun&sky effect..
9.) know the difference between copy and instance.. simple but effective
10.) purge undo window, specially commands on the list that eat up memory..
11.) this i part of my resource management, i always shutoff my antivirus while rendering (or dont install at all), specially anti-virus like norton and mcafee (which sucks bigtime) this are memory hog application, same as old Nero updates, always check taskbar once a while, even screensaver and windows eyecandy specially in vista, i turn them off back to basic.
12.) use map efficiently, instead of modelling small details, in par with [#7.]
13.) use xref scene (but not sure duh, havent tried it yet)
14.) use polygon friendly 3dsmax plugins such as mootools' polycruncher, best of all its free tongue
15.) be wary of iteration levels when making curves/meshsmoothing
16.) when using irradiance map, check interpolation, par it with reflection and refraction interpolation on the submenu.. (match it with IR min/max rate with interpolation min/max rate)
17.) caustics are time killer
18.) first pass, brute force vs. irradiance map, (case to case basis)
19.) hardcore noisethreshold and AA subdivision rate, (case to case basis)
20.) be wary of glossy reflection and frosted materials..(case to case basis)
21.) instead of using dof in physical cam, Photoshop can do the trick with an ease with zbuffer channel or plugins like Alien Skin's DoF and DoF Generator PRO by Richard Rosenman.
22.) post process can short the rendering workflow, proffesional composition programs like Autodesk's Combustion and the likes.. just know variations in renderchannels in vray render elements (F10).
23.) Evermotion Archshaders and Archinterior/Exterior Materials are on overkill settings, dont be lazy to edited it once a while, dont just copy and salvage someone's craft as it is.
24.) Irradiance and Light Cache (save to file), skip the computation when using the same sets and scene over and over again.
25.) balance with the resolution output and irradiance map settings.
26. before u place all the shaders. try to override first the materials in the rendering parameters(global switches.).to make sure all polygons are modelled correctly for test rendering so that you would knw the types of shaders u placed individually and u can trace easily which materials could possibly caused the rendering longer.
27).too many lights can also coz the overkill of the rendering.
28). use alwayz the default parameters for fast test renders..
29).For me i prefer ADAPTIVE QMC rather than Adaptive Subdivision...
30).Check your Raycast Parameters too..Like render region division,region sequence etc..
31)If ure using vray displacement mode,try to limit the area if 2d mapping ang setup for it eats a lot of ram.
32) Use 64bit Max
33) The use of X-refs is invaluable--primarily due to their ability to link large sections of scenery together and provide a means to keep your master scene to ballooning to an unwieldy size.
34) Attach those objects - 3ds Max is much more efficient working with 9000 10k polygon objects than 200,000 1k polygon objects. Attaching all the components that are not being individually animated adds a significant amount of speed and flexibility to the scene you're working on.
35) Geometry Proxies - Ah yes, my new favorite tool! A geometry proxy is an optimized piece of geometry that is designed to load and render much more efficiently in specific render engines such as Mental Ray & Vray.
36) Bitmap Proxies - Bitmap proxies are a great way to minimize the amount of RAM that you are expending on a scene.
37) Centralize your data - Centralizing your data adds a level of organization to any project.
38) Work Locally and Incremental Saves - Why you ask? Well, as you save to the network share, you can run into some traffic issues which can on occasion cause crashing and corrupted documents
39) Layers, Groups and Selection Sets - Any organized 3ds Max user has used these at one time or another, though some more than others.
40) Maxscripting - it can bring repetitive and laborious tasks to heal. This has saved me countless of production hours and has allowed us to tackle projects that would be impossible with the stock tools in 3ds Max.
41) learn Photoshop and other compositing softwares (AE, Combustion). you will save hell a lot of render times.
42) understand photography. train your eyes. its good to have a vision of what you want to achieve before you start with your rendering workflow. for example, you'll know when to cancel a render process (region render) rightaway soon as you spot something wrong on your buffer rather than waiting for the whole scene to finish then realizing something's wrong (so much time wasted already) and you have to re-render again. trained eyes helps to influence clients and manage them to understand your vision.
43. Bitmaps - these tend to take up large amounts of RAM, especially if the maps are large. Since textures are managed by 3dsmax, VRay has no direct control over their memory usage. However, you can use the Bitmap pager settings of 3dsmax to reduce the RAM taken up by bitmaps. Turn on and adjust the bitmap pagers into a higher amount, this will address your computer to process the memory in using bitmaps. This is especially useful in rendering large image.
44. You might want to check the multi-threading option if you are using a dual processor.
45. Use Low resolution for rendering tests.
46. Use Rendering Region: render only what interests you. Time to time check your shaders, verify the little differences.. and quickly find the result you’re looking for.
47. Do not add Glossy effects. Add it just when you think that the scene works fine.
48. Geometry - scenes with lots of objects and/or triangle counts require more memory to render. There are several ways to reduce this amount:
-Adjust the raycaster settings in the System rollout (reduce Max. levels, increase Min. leaf size, increase Face/level coefficient, switch from Static to Dynamic Default Geometry).
49. Displacement mapping - objects displaced with the 2d displacement mapping method may require a lot of RAM to render, especially with large displacement maps. If this is the case, use the 3d displacement mapping method. Also, if you have several distinct displacement modifiers with the same displacement map, it is better to replace them with one modifier, applied to all the necessary objects. This is because each modifier will take RAM for the displacement map, separately from other modifiers, even if they have the same map.
50. Bitmap filtering - Summed area filtering uses much more memory than Pyramidal filtering. Use summed-area filtering only for smaller bitmaps
51. Shadow maps - these may also take up significant amounts of RAM. Again, these are managed by 3dsmax and VRay has no direct control over their memory usage. To reduce memory usage, you can switch to raytraced VRayShadows instead.
52. Image buffer - large output resolutions require a significant amount of RAM to store the final image. Additional G-Buffer channels increase that amount. There are several ways to reduce this amount:
-Use the 3dsmax Bitmap pager, if you are rendering to the 3dsmax default VFB.
-If you use VRay's own VFB, use the Render to VRay raw image file option and then use the VRay raw image file viewer to convert the resulting file to a different format.
53. Image samplers (AA) - the image sampling algorithms of VRay require some amount of RAM to hold all the data for the sampled image. This amount can be quite large, depending on the chosen bucket size and sampling rate. To reduce that amount:
-Reduce the bucket size.
-Switch to a different image sampler - for example, the Adaptive QMC sampler uses less RAM than the Adaptive subdivision sampler.
54. Global illumination caches - irradiance maps, photon maps and light maps all require additional memory to store them. Each of these has different methods for controlling its memory usage:
-For the irradiance map - the memory depends on the number of samples in the map; you can reduce this number by using lower Min/Max rate, and more loose threshold values (higher Color threshold, higher Normal threshold, lower Distance threshold).
-For the photon map - the memory depends on the number of photons stored. You can reduce this number by reducing the Diffuse subdivs for the lights, or by increasing the Max. density.
55. If not necessary, adjust your trace depth contols to a lower amount.
56. Even though you select the VRAY VFB as your output, the 3dmax VFB is stil created and thus taking additional memory. If you want to reduce that memory. you need to uncheck the "GET RESULOTION FROM MAX" option. Set the 3dmax resolution to lower value like 100 x 100, and then select your real output resolution in the VRAY VFB option
57. inspect your scene -was there are lots of unused polys, was there are lot of models that only clatters the scene but are not viewable on camera, was there are lots of unused materials on the editor....
meaning, sometimes we think that our render setup is hampering the rendertime, but if we just inspect our scene, the things mention above are factors that affects.
58. another one. sometimes our model in autocad was located far from the axis origin, this happens most of the time. then once we link it up to our rendering program, we just let them as it is. This also prolong the rendertime when executed. Bring it back in 0,0 axis position while still in autocad.
59. Overlapping of Models and meshes. - a scene with much of these will take longer time to render. You need to tweak your setting into higher so as to cover up those splotches.
60. Rendering Large Image - rendering a large output image takes longer time when rendered as a whole. Use alternatives, like split rendering, or some render plugins like Super Render - wherein the scene will be subdivided into bucket window then automatically combining them after the last bucket.
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