[Not a Number]

How can anything digital be stepless? The clock, the individual bits etc.

http://wiki.hydrogenaud.io/index.php?title=Myths_(Vinyl)

Myth: Vinyl is better than digital because the analog signal on the vinyl tracks the analog signal exactly, while digital is quantized into steps

Frequency resolution

The Nyquist-Shannon sampling theory states that continuous-time (analog) signals and their corresponding discrete-time (digital) signals are mathematically equivalent representations of any bandwidth-limited signal, provided the sample rate is higher than 2X the bandwidth. All relevant advantages and disadvantages result from implementation details rather than analog versus digital signal representation method. Perhaps the most common method of storing a digital signal is with pulse code modulation (PCM). PCM is used on CDs and DVD-A.

PCM is sometimes characterized as producing a jagged, "stair-step" waveform. This is only partially correct; analog-to-digital conversion (ADC) does indeed use a sample-and-hold circuit to measure an approximate, average amplitude across the duration of the sample, and digital-to-analog conversion (DAC) does the same kind of thing, generating a rectangular-ish waveform, but this output is always then subjected to additional filtering to smooth it out. Effectively, the ADC output sample values are interpreted as a series of points intersected by the waveform; the DAC output is a smooth curve, not a stair-step at all. Additionally, modern ADC and DAC chips are engineered to reduce below the threshold of audibility, if not completely eliminate, any other sources of noise in this conversion process, resulting in an extremely high correlation between the input and output signals. (Perhaps a better explanation: xiph.org's "Digital Show & Tell" video)

A related myth is that components of the signal near the Nyquist frequency must be square waves on CD (or digital media), and that vinyl (or any analog media) preserves pure sine waves. The premise is false. A square wave, or any wave that's not a perfect sine wave, is the sum of multiple pure tones (sine waves), by definition. So if you have a pure 22.05 kHz signal on CD (i.e., sample values +n, -n, repeatedly), the DAC may first construct a square wave, but the reconstruction filter then filters out everything above the Nyquist frequency, leaving behind a sine wave. The principle is the same even in complex waveforms. The end result is that the uppermost frequency components on CD are no closer to being square waves than they are on vinyl.

[rangercarp]

I hope many people are happy in February.

I hope so too.... Now what do you think is going to make people happy in February?

[stevebrot]

"Installed in the lens barrel are a position sensor which detects the position of the focus lenses steplessly, rather than in steps, and a sensor which detects the SDM’s rotation speed. Obtaining position and speed data simultaneously optimizes the balance between autofocusing speed and focusing precision, despite the lens’s large open aperture of F1.4 and its very shallow depth of field"

I wonder what tells it where to stop? Part of the efficiency of PDAF is provided by knowing current focus position with very high precision and using the calculated number of steps (similar to a numeric controller) to to projected the projected stop point. Canon does this so well (or so they say), they don't even recheck position against the sensor.


Steve

[monochrome]

I hope so too.... Now what do you think is going to make people happy in February?

I know nothing, but there is a certain DA*Wide Zoom promised for some time (early?) next year, and discussion of an APSc flagship body, and there’s a significant camera show in late February, as I recall.

[stevebrot]

How can anything digital be stepless? The clock, the individual bits etc.

The answer is "relatively stepless"...unless of course the movement itself is not digital. The announcement sounds a little like Ricoh is not using a stepping motor.


Steve

[stevebrot]

The Seiko Seikosha shutter in the K2 was described as stepless. What I believe that meant, and this means, is the intermediate stops are infinite (or so small as to be deemed infinite).

It and most other electronically controlled shutters since are stepless in the sense that they are not governed by discrete metal steps constraining curtain timing. OTOH, the curtain spacing on an electronically-timed shutter is only as good as the step-wise precision of the clock chip.


Steve

[rangercarp]

I know nothing, but there is a certain DA*Wide Zoom promised for some time (early?) next year, and discussion of an APSc flagship body, and there’s a significant camera show in late February, as I recall.

I figured that is what you were getting at. The flagship APSc would indeed make me happy!

[monochrome]

It and most other electronically controlled shutters since are stepless in the sense that they are not governed by discrete metal steps constraining curtain timing. OTOH, the curtain spacing on an electronically-timed shutter is only as good as the step-wise precision of the clock chip.


Steve

While I intended the post to be an illustrative analogy, I’m certainly better informed about electronic shutters now.

[leekil]

I wonder what tells it where to stop? Part of the efficiency of PDAF is provided by knowing current focus position with very high precision and using the calculated number of steps (similar to a numeric controller) to to projected the projected stop point. Canon does this so well (or so they say), they don't even recheck position against the sensor.

If it knows the position and speed, it can continue to run the motor for a specific period of time so it arrives at the desired position. This also requires the stopping being precise.

This still means it is "relatively" stepless, I would think, due to the precision of the calculations being done. But all of this is also primarily compared to the screw-drive focusing, I would think, where there minimum movement possible is significantly larger for that mechanism. I don't know the details of the older SDM workings, but presumably they don't rely on the above described position and speed data.

[ThorSanchez]

http://wiki.hydrogenaud.io/index.php?title=Myths_(Vinyl)

I once worked with a technician who was a vinyl acolyte always arguing for the inherent superiority of that over digital. I said, basically, "Nyquist Theorem". He said "yeah, well, it's just a theorem, it's not it's really a fact so I don't believe it."

[Dipsoid]

I once worked with a technician who was a vinyl acolyte always arguing for the inherent superiority of that over digital. I said, basically, "Nyquist Theorem". He said "yeah, well, it's just a theorem, it's not it's really a fact so I don't believe it."

I read an interesting article a while back by I believe it was the creator of FLAC, in which he dispelled the myth that digital samples create stepped square waves, even had a video showing how a DAC interpolates stepped waves to perfect sine waves. As a vinyl listener myself I get annoyed by people proclaiming superiority of analog systems with vacuum tube amps as being superior over anything digital.

[Mark Ransom]

I read an interesting article a while back by I believe it was the creator of FLAC, in which he dispelled the myth that digital samples create stepped square waves, even had a video showing how a DAC interpolates stepped waves to perfect sine waves. As a vinyl listener myself I get annoyed by people proclaiming superiority of analog systems with vacuum tube amps as being superior over anything digital.

Is this the one you were thinking of?

You Tube

You Tube

[SSGGeezer]

Is this the one you were thinking of?

D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org) - YouTube

Thanks for the time sink Mark! Really well done and informative video though. Now another person on YouTube to follow.

[Dipsoid]

Is this the one you were thinking of?

D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org) - YouTube

That's it!

[Winder]

Some years ago, when I was a contractor at NASA, NASA came up with a buzz phrase for new missions: Faster, Better, Cheaper (I think this was supposed to make Congress feel better about the NASA budget)
The (unspoken to the brass) response from those of us in the trenches was "pick two out of three"!

Actually that is how products evolve. Faster, Better, Cheaper. If you could have bought a K-1 10 years ago how much would it have cost? Is the K-1 not faster, better, and cheaper than any comparable product on the market 10 years or even 5 years ago? The K-1 would have been a $10,000+ camera 10 years ago.