Scanning DPI

[Francisco Disilvestro]

Bensyverson, I know something about signal processing, anyway this may be getting off topic.

High sampling rate and one bit depth is a different method than sampling at a frequency just above the Nyquist limit and several bith depts, It is like Pulse Width Modulation vs. Pulse Amplitude modulation. In the first the amplitude does not matter because the information is in the pulse width. In the latter, the information is in the amplitude and that is why you need several bit depth (practically limited as you say by SNR)
My point is that there is not an in between. It is not like as you increase sampling rate you can lower bit rate in a linear way. They are 2 different methods. PAM needs a sampling rate above twice the max frequency to be able to reconstruct the signal, PWM needs a rate over 1 order of magnitude higher than max frequency of your input signal or more. That's why the Korg 1 bit sound recorders use 2.8 or 5.6 MHz.
In PAM you measure the amplitude of the imput signal, in PWM you compare it to a reference signal. It is a different approach.
The way to reconstruct the signal is also different. With PAM you need a Digital to analog converter, with PWM a low pass filter will do (or an integrator).
You are right that you could create a full color image with 1 bit per pixel trough a Bayer filter, the limitations of the human eye will do as a low pass filter
I also agree that histogram do not correlate directly to image quality. It is just that in the 1 bit high frequency sampling approach, a histogram to be useful should be constructed from pulse width data and not from signal amplitude.

[Ben Syverson]

I also agree that histogram do not correlate directly to image quality. It is just that in the 1 bit high frequency sampling approach, a histogram to be useful should be constructed from pulse width data and not from signal amplitude.

No argument there -- talk to Adobe!

In the meantime, it's important for photographers to know that they shouldn't rely on the histogram alone.

[sanking]

In the meantime, it's important for photographers to know that they shouldn't rely on the histogram alone.

Do you believe this is a wide spread problem? I have personally never known a single photographer who relied on the histogram alone!!

Sandy

[Ben Syverson]

It is a widespread problem -- nearly every photographer I have known has had an irrational fear of histogram gaps.

[sanking]

It is a widespread problem -- nearly every photographer I have known has had an irrational fear of histogram gaps.

You need to document this and get it published in a good peer journal. It could be the first step in federal recognition of the problem, which could lead to funding for more research and support groups.

Sandy King

[Mike1234]

I don't use histograms at all.

[Francisco Disilvestro]

Histograms are useful to get additional information about the image, not to evaluate it.
Are those photographers who fear gaps expecting a particular shape from the histogram? Just tell them to convert to LAB mode and check the histogram in the a & b channels. I hope they won't try to adjust levels to bring back a nice shape

[Ken Lee]

"Its the all the fault of histograms you know"

"It is a widespread problem -- nearly every photographer I have known has had an irrational fear of histogram gaps."

"You need to document this and get it published in a good peer journal. It could be the first step in federal recognition of the problem, which could lead to funding for more research and support groups."

I actually had my histograms removed when I was a young man - my parents insisted !

Don't be shocked - back in those days, it was fairly common where I lived. Lots of guys got histogramectomies. If I had to do it today, I'm not sure I could go through with it.

Thanks Sandy - I feel better, just being able to talk about it !

[sanking]

[I][COLOR="DimGray"]

I actually had my histograms removed when I was a young man - my parents insisted !

Don't be shocked - back in those days, it was fairly common where I lived. Lots of guys got histogramectomies. If I had to do it today, I'm not sure I could go through with it.

Ken,

I am guessing that your disease was diagnosed back in the days when most everyone was using MAC systems for image processing and the histogramectomy was the only recommended cure. With the popularity of PCs cryotherapy is proving a popular alternative to the histogramectomies. Several versions of Windows have proven to be highly efffective at freezing the historgram, which of course renders it totally inoperative, and saves the the ordeal of removing the disease from the host organism.

Sandy

[Jim Graves]

It is a widespread problem -- nearly every photographer I have known has had an irrational fear of histogram gaps.

Well, as one of the probably 98% of the population of this board that understands about 2% of the technical discussion herein ... I'd have to agree with Bensyverson ... when I see one of those gapped histograms, I just assume I've completely screwed up my image ... why else would it look like that? ... and that way too much of the original information is now gone and were I to try to print it there would be a huge decrease in detail and tonal values. So, I back up and start over.

This discussion thread has been very enlightening on that and several other valuable points.