Technical question regarding Video Preview options in Seq Settings

Question

I am trying to wrap my head around some of the unique differences between FCP7 and PrP 5.5. What is the function of the Video Preview choices in the Sequence Setting menu? It seems standardized to I Frame Only MPEG with  other options depending on what your source footage is. Why would I use this setting as opposed to 1080 (for an AJA sequence made from Prores footage) or P2 (for an Adobe seq built from the same Prores footage) or Red which gives you no options then the one I just mentioned?
In FCP when things were rendered they were used when I would export the sequence. Is PrP 5.5 the same? If I am previewing a 1080 sequence in I Frame Only MPEG, does that mean on output the whole entire sequence and effects need rendering? What is the best work flow when using Adobe or AJA sequences in regard to this Video Preview setting? It is so different from what I am used to I want to make informed choices.

Answer 1

Maximum Bit Depth is only suitable when ingesting 4:2:2 material and exporting with AJA or BM
Oh, man... not again. This is not true, at all. Maximum Bit Depth has nothing to do with 4:2:2 AJA or BlackMagic. And Maximum Bit Depth is not just for use with 10-bit or  greater source footage. It can be used with 8-bit material--DV, H.264,  MPEG2, anything--to great benefit.
(The following is copied and pasted since I've written it so many times...)
What Maximum Bit Depth  (either in the Sequence Settings or in the Export Settings) does is  enable Premiere Pro to render and composite in 32-bit floating point  color. It has nothing (or at least, little) to do with the source  footage, but controls how effects and transformations that shift pixels  around are rendered. Any effect in the Effects panel that has a 32-bit  badge on it will benefit from Maximum Bit Depth--the expense is greater  memory requirements and processing time, but the payoff is a higher  degree of color fidelity and precision in the rendered image. Gaussian  Blur, for example, is a 32-bit effect that will show a great difference  between when it is rendered with MBD on versus when it is off--even if  you're rendering/exporting to an 8-bit format, like DV.
From Karl Soule's article on this topic, The Video Road – Understanding Color Processing: 8-bit, 10-bit, 32-bit, and more:
A DV file with a blur and a color corrector exported to DV without the max bit depth flag. We  will import the 8-bit DV file, apply the blur to get an 8-bit frame,  apply the color corrector to the 8-bit frame to get another 8-bit frame,  then write DV at 8-bit.
A DV file with a blur and a color corrector exported to DV with the max bit depth flag. We  will import the 8-bit DV file, apply the blur to get an 32-bit frame,  apply the color corrector to the 32-bit frame to get another 32-bit  frame, then write DV at 8-bit. The color corrector working on the 32-bit  blurred frame will be higher quality then the previous example.
A DV file with a blur and a color corrector exported to DPX with the max bit depth flag. We  will import the 8-bit DV file, apply the blur to get an 32-bit frame,  apply the color corrector to the 32-bit frame to get another 32-bit  frame, then write DPX at 10-bit. This will be still higher quality  because the final output format supports greater precision.
A DPX file with a blur and a color corrector exported to DPX without the max bit depth flag. We will clamp 10-bit DPX file to 8-bits, apply the blur to get an 8-bit  frame, apply the color corrector to the 8-bit frame to get another  8-bit frame, then write 10-bit DPX from 8-bit data.
A DPX file with a blur and a color corrector exported to DPX with the max bit depth flag. We will import the 10-bit DPX file, apply the blur to get an 32-bit  frame, apply the color corrector to the 32-bit frame to get another  32-bit frame, then write DPX at 10-bit. This will retain full precision through the whole pipeline.
A title with a gradient and a blur on a 8-bit monitor. This will display in 8-bit, may show banding.
A title with a gradient and a blur on a 10-bit monitor (with hardware acceleration enabled.) This will render the blur in  32-bit, then display at 10-bit. The gradient should be smooth.
What Maximum Bit Depth does is allow  Premiere Pro's rendering engine to have more room to run, with a higher  degree of precision. It's important to remember that rendering  internally is different than exporting--and even when you're "rendering"  previews, you're actually exporting, because you're creating composited  video files of one sort or another. That's why there is a Maximum Bit  Depth checkbox in the Sequence Settings--that affects preview files, not  exports. When you're using hardware MPE, you're always operating in  MBD--or more specifically, you're rendering in 32-bit linear color.  Generally, this is "better," though I've lamented about the negative  effects of linear color processing, e.g. annoying opacity differences on  dissolves, shaggy alpha channels, etc.
The bottom line is  that Maximum Bit Depth allows Premiere Pro to generate better  (subjective), more technically accurate (objective) output, regardless  of the input and output format.