… for Codecs & Media

Tip #1102: What is a Render File?

Larry Jordan – LarryJordan.com

A render file is a media file calculated based on the effects applied to a source clip.

Since all NLEs are non-destructive editors (leaving original media intact), render files are created when you alter an original clip, create a clip via a generator or use a still image in the Timeline. Those alterations need to be turned into media. That process is called “rendering.”

Essentially render files are new media files that match your project/sequence settings that your NLE uses instead of the original clips. They effectively ‘replace’ the original media and the NLE will refer to them instead of the original media once they’ve been rendered.

If you make additional changes to a rendered clip, the NLE will delete the old render file and it will be replaced by a new render file.

Generally, render files are retained by the NLE if you delete a clip from the timeline, which saves time in case you put it back in.

To pick up storage space, you can delete render files. If that file is needed again, the NLE will re-render it.

Once a project is complete, render files can be deleted. If they are needed in the future, the NLE will re-render them, as well.

… for Codecs & Media

Tip #1105: What is Sharpening?

Larry Jordan – LarryJordan.com

Sharpening means enhancing the contrast of edges in an image.

This article, written by Henry Guiness, first appeared in Photography.Tutsplus.com. This is a summary.

We have all heard the term “sharpening.” But what is it and how do we apply it? There are three main reasons to sharpen your image: to overcome blurring introduced by camera equipment, to draw attention to certain areas and to increase legibility.

Before I explain how to sharpen, we need to understand that sharpness is subjective.

Sharpness is a combination of two factors: resolution and acutance. Resolution is straightforward and not subjective. It’s just the size, in pixels, of the image file. All other factors equal, the higher the resolution of the image—the more pixels it has—the sharper it can be. Acutance is a little more complicated. It’s a subjective measure of the contrast at an edge. There’s no unit for acutance—you either think an edge has contrast or think it doesn’t. Edges that have more contrast appear to have a more defined edge to the human visual system.

Sharpening then, is a technique for increasing the apparent sharpness of an image. Once an image is captured, Photoshop can’t magically add more details: the actual resolution remains fixed. Yes, you can increase the file’s size but the algorithms any image editor uses to do so will decrease the sharpness of the details.

In the image in the screen shot, the author mimicked the Unsharp Mask effect in Photoshop. The first image is the original file, the second is a blurred copy, the third is the one subtracted from the other so as to detect the edges, and the fourth is the original image sharpened using the edge layer. Unsharp masking is the oldest sharpening technique. It subtracts a blurred (unsharp) copy from the original image to detect any edges. A mask is made with this edge detail. Contrast is then increased at the edges and the effect is applied to the original image. While unsharp masking was originally a film technique, it’s now the basis of digital sharpening.

The article continues with sharpening settings and illustrations of both good and bad sharpening, along with links to learn more.

… for Codecs & Media

Tip #1068: When to Choose JPEG, PNG or TIFF

Larry Jordan – LarryJordan.com

Pick the codec that works best for your project.

A codec is the mathematical formula that determines how to convert light, or sound, into binary digits for the computer to store or display. While there are a LOT of still image codecs, there are only four that you’ll need to choose between for most of your video projects:

• PSD
• JPG
• PNG
• TIFF

So, which should you choose? Here are some tips.

PSD

This is the native Photoshop format.

Use this when you need to retain the ability to edit the elements of an image or when you want to enable, or disable, specific layers within the image.

NOTE: For best results, always embed media into the Photoshop file.

JPG or JPEG

This is a highly-compressed file best used for final distribution. Good image quality in a very small file size.

Part of compressing a JPEG file involves throwing away color data and reducing some of the image quality. While this is almost always OK for images destined for the web, it is not a good idea for any image that you want to edit.

NOTE: Compressing an already compressed file will materially damage quality.

PNG

This is a modestly compressed image format. Excellent image quality with a large file size.

This is a more modern format than TIFF and is the best choice for outputting finished images at high quality. While you can’t reedit a PNG image the way you can a PSD, this provides excellent image quality. PNGs, unlike JPEG, supports an alpha channel for transparent image elements.

The only limit of PNG is that it is only supports 8-bit color.

TIFF

This is a lightly compressed image format, providing excellent image and color quality with a large file size.

TIFF is my go-to still image format. Supporting up to 10-bit color, alpha channels and essentially lossless images, it has been around for a long, long time.

The only limitation of TIFF is that, unlike PSD, you can’t edit elements within the image.

… for Codecs & Media

Tip #1070: What Determines Storage Performance?

Larry Jordan – LarryJordan.com

Aerial density, RPM and whether an SSD is in the mix all affect storage performance.

Seagate published an interesting article, titled: Choosing High Performance Storage Isn’t Just About RPM. This is a summary.

The performance of a hard drive is most effectively measured by how fast data can be transferred from the spinning media (platters) through the read/write head and passed to a host computer. This is commonly referred to as data throughput and typically measured in gigabytes (or gigabits) per second. In either case, data throughput is directly related to how densely data is packed on the hard drive platters and how fast these platters spin.

Higher revolutions per minute represent a faster hard drive, but the rate of media transfer is just as important for data storage solutions.

For the areal density specification, we can measure data density on a hard drive in two ways: bits per inch (BPI) and tracks per inch (TPI). As tracks are placed closer together, TPI increases. Similarly, as data bits are placed closer and closer to each other along a track, BPI increases. Together, these represent areal density.

As a rule, when areal density increases on a hard drive, so does data throughput performance. This is because the data bits pass by the read/write head of the hard drive faster, which leads to faster data rates.

For the RPM specification, platters need to spin faster to increase performance in a hard drive. This results in moving the data bits past the read/write head faster, which results in higher data rates. Hard drives have been engineered with spin rates as low as 1200 RPM and as high as 15K RPM. But today’s most common RPM rates, in both laptop and desktop PCs, are between 5400 and 7200 RPM.

Given two identically designed hard drives with the same areal densities, a 7200 RPM drive will deliver data about 33% faster than the 5400 RPM drive. Consequently, this specification is important when evaluating the expected performance of a hard drive or when comparing different HDD models.

However, when moving to a solid state hybrid drive (SSHD), RPM is largely irrelevant. Why?

SSHD design is based on identifying frequently used data and placing it in the solid state drive (SSD) or NAND flash portion of the drive. NAND flash media is very fast, partly because there are no moving parts—since it’s made of solid state circuitry. Therefore, when data is requested by host computers there is typically not a dependence on pulling this data directly from the spinning media in the hard drive portion.

Sometimes, however, data will be requested that is not in the NAND flash, and only during these instances does the hard drive portion of the device become a bottleneck. Since the technology is so effective at identifying and storing frequently used data in the NAND area, SSHD technology is much more efficient in delivering data to a host computer quickly.

In tests conducted by Seagate to illustrate this article, the fastest performance for an SSHD drive came from one where the platters only spun at 5400 RPM.

Here’s a link to the full article.