Mistakes On Key Lessons

JH
John Honovich
Mar 11, 2013
IPVM

Please review the IPVM Class Key Lessons document. This will be the basis for Thursday's class and next week's final.

Report below any mistakes you believe you have found on the final. If we accept them, they will be worth 1 bonus point each on the final plus bragging rights!

TB
Tom Bragg
Mar 11, 2013

Under the resolution section, second to last statement, a 5mp camera has the equivalent number of pixels as 15 analog cameras....... analog cameras have tv lines not pixels.

JH
John Honovich
Mar 11, 2013
IPVM

Tom, analog cameras are encoded (whether in a DVR or encoder appliance, etc.) and the maximum pixel count is VGA / 4CIF. A 5MP camera has ~15 times the pixels of VGA / 4CIF encoded cameras.

TB
Tom Bragg
Mar 11, 2013

Ok you got me on the encoders.......but I will be back!

JH
John Honovich
Mar 11, 2013
IPVM

Keep it coming!

RH
Richard Heilweil
Mar 12, 2013

In the review, pg 9 paragragh 3, you state "Digital zoom is irrelevant to PTZ performance. Only optical zoom matters. Digital zoom is more of a marketing trick than any practical difference." I believe this is not always true assuming good lighting. If the PTZ is left fixed in a position (PTZ function used only to change area of interest without having to physically move the camera) with the appropriate PPF based on the optical zoom setting, digital zoom can be very useful both in a 720 and 1080. At best the statement does not have enough information to be true or false.

JH
John Honovich
Mar 12, 2013
IPVM

As we discussed in class, it is irrelevant in selection / deciding which PTZ is better. Obviously, digital zoom is useful. I can see where the wording is unclear. I've changed it from 'performance' to 'selection'

+1 for you!

Background: see Digital zoom tutorial

RH
Richard Heilweil
Mar 12, 2013

Thanks John, however I take further issue wven with wording revised. In selcting between an analog digital zoom (worthless) and an HD where there is a value. So if zoom on playback is an important factor all other things considered equal, digital zoom is relavent. Not trying to split hairs, I'm just sayin' :)

JH
John Honovich
Mar 12, 2013
IPVM

Digital zoom is not the differentiator there. It's resolution / pixel count. I am not trying to split hairs either but you don't pick the HD PTZ over the analog one because it has digital zoom, you do so because of the higher pixel count.

RH
Richard Heilweil
Mar 12, 2013

You are one for wording, I will give you that! :) Would you agree that the higher pixel count inturn provides for better digital zoom? If PTZ with digital zoom is the objective of the customer..... follow my logic? If not where am I going wrong? Happy to take this off line if I am causing confusion.

JH
John Honovich
Mar 12, 2013
IPVM

Digital zoom becomes more useful with higher resolution but digital zoom is still not a reason to select one PTZ over another because all PTZs have far more than acceptable digital zoom levels.

RH
Richard Heilweil
Mar 12, 2013

My objection to your satement that "all PTZs have far more than acceptable digital zoom levels" is based on Analog vs MP. This statement is simply not true without clarifying that you must be refering to MP PTZs. Digital zoom on analog is useless. From the section in the reveiw guide references are made to both analog and MP PTZ hence the reason for clarification.

JH
John Honovich
Mar 12, 2013
IPVM

Richard, with regards to analog and MP PTZ digital zoom levels: The zoom levels are fine on either camera type. It's not as if more digital zoom would make either analog or MP cameras better.

Put it this way, "All PTZs have far more than acceptable digital zoom levels, but some have greater pixel count which can improve performance." I do not see the reason to change anything as it should be obvious that the difference / advantage of MP comes from pixels, not digital zoom.

CV
Charles Volschenk
Mar 12, 2013

Hi John,

I assume you are awarding marks for "conceptual" mistakes, rather than literary/typo ones?

I have found 8 of the latter - one example being P6 para5 "have limited lens options and are poor are capturing fine details". Another would be P18 para9 reads exceptionally difficult and it seems some info/wording is missing in my opinion.

But reading through the whole document, I didn't find anything which I found to be "conceptually incorrect". Well done - a useful document to have indeed.

Regards

Charles

JH
John Honovich
Mar 12, 2013
IPVM

Charles, Thanks. I've certainly give a +1 for a handful of typos and the poorly phrased paragraph. I've fixed those two already. Let me know what else you have. Thanks again!

PK
Pushkar Katiyar
Mar 12, 2013

I found this under the heading "WDR / Low Light Class"

"For example, just because manufacturer A rates their cameras at 58dBs while B rates theirs at 111dB does not guarantee A will outperform for WDR."

Shouldn't it say "does not guarantee B will outperform for WDR."?

I understand that higher the WDR rating, better the WDR performance (everything else being equal, well technically)

JH
John Honovich
Mar 12, 2013
IPVM

Pushkar, it should be as you say - higher dB rating does not guarantee B outperforming. Good Find! +1

PK
Pushkar Katiyar
Mar 12, 2013

Page 10:

Many fisheye panoramic cameras require PTZ systems to dewarp the distorted fisheye view inside the VMS’s client.

Shouldn’t it be:

Many fisheye panoramic cameras require VMS systems to dewarp the distorted fisheye view inside the VMS’s client.

Page 14:

The two main drivers of F numbers are lens length and lens diameter. All things equal the longer the lenses, the higher the F number and the smaller the lens diameter, the higher the F number.

Shouldn’t it be:

Diameter of the IRIS (opening) and not the lens diameter.

JH
John Honovich
Mar 12, 2013
IPVM

Pushkar, yes, many fisheye panoramics require VMS systems, not PTZs to dewarp. Good find! +1

As for the drivers of the F number, I am trying to emphasize the maximum diameter which is physically limited by the diameter of the lens. I changed it to 'lens iris diameter' and added in the following sentence to emphasize this point: "While most lens irises can be made narrower, the most important metric is how wide it can be, as this determines the lowest possible F number."

RH
Richard Heilweil
Mar 12, 2013

You make a valid point..... of course. As I stated you are one for the use of words. I will be on the lookout during the final and I'm sure I'll get bagged on a few questions with double negatives or some other little nuances.

TB
Tom Bragg
Mar 13, 2013

On page 13: Minidones are commonly used.......

Did we not discuss one big reason was "esthetics"

JH
John Honovich
Mar 13, 2013
IPVM

Tom, here's the whole statement, "Overall, minidomes are more commonly used than full sized domes due to a preference for small size and low costs. "

The small size is the key to improved aesthetics, but it is important to specifically mention aesthetics as well.

+1, good catch!

TB
Tom Bragg
Mar 13, 2013

Page 14 mid way down- Auto back focus/auto focus......

"it is only available on a minority of IP camera's today"

Yet in your note Auto Back Focus (ABF) Preference Statistics it states: Auto back focus has become a more and more common feature in IP cameras in the past 1-2 years, with manufacturers both major and minor adding it to the new products.

Is that a contradiction worthy of correction?

JH
John Honovich
Mar 14, 2013
IPVM

Tom, both statements are actually true, especially when you look at the whole statement, "It is only available on a minority of IP cameras today and typically those are premium / professional versions."

A lot of manufacturers are adding auto back focus but it's typically only to their top tier lines. Maybe in a year or two, it will reach the majority, but it's not there yet.

TB
Tom Bragg
Mar 13, 2013

Page 14 3rd paragraph from the bottom.

The two main drivers of F numbers are lens length and lens diameter.....

Yet in your note: it states: Technically, f stop contrasts the length of the lens and the diameter of the iris (i.e., L/D).

Or does (i.e., L/D) mean lens diameter?

Not sure on this point? F-stop is not an easy concept to understand.

JH
John Honovich
Mar 14, 2013
IPVM

Tom, the L/D formula means length of the lens (l) divided by the diameter (d) of the iris/lens.

TB
Tom Bragg
Mar 13, 2013

Page 16, second paragraph (e.g., a 40 ppff = 1600 pixels/40 feet)

What is ppff ? Should it simple be ppf?

[IPVM NOTE: Yes, that is a typo. Fixed]

TB
Tom Bragg
Mar 13, 2013

Page 17, 4th paragraph "Be careful when people ask for how far can a camera see X....... width of FoV cannot be magically and continuously expanded"

Unless you offer a PTZ as the solution ??

JH
John Honovich
Mar 14, 2013
IPVM

Nothing can be 'magically and continuously expanded', not even a PTZ.

The full quote is "With the right lens a camera can ‘see’ very far away but the width of FoV cannot be magically and continuously expanded." I think this clearly explains that lens adjustment can support seeing farther away (like PTZs) but that it has limits that need to be appreciated.

TB
Tom Bragg
Mar 13, 2013

Page 17- Second last paragraph

Should that not be Subjective not "Objective"

IPVM NOTE: The quote is "Objective, clearly definable, image quality levels do not exist." We are referring to objective, meaning levels that are independent of opinion. We are saying they do not exist and, therefore that these levels are subjective.

LS
Lonny Sutton
Mar 14, 2013

Chapter 5 - Paragraph 5 - "For examples, in applications where a fixed camera most monitor objects far away"

Should read "For example, in applications where a fixed camera must monitor objects far away"

PK
Pushkar Katiyar
Mar 21, 2013

Page 32 -

The necessity of VLANS for increasing bandwidth in an existing network is a myth; VLANs are only able to segregate traffic, not increase gross bandwidth capacity. Moreover, VLANs cannot stop video surveillance from overwhelming the rest of the network if problems occur.

Do you mean to say - save (or) reduce bandwidth? (As described on "VLANs for Surveillance" article)

JA
John Alemparte
Mar 21, 2013

Actually in terms of the "myth" there is a misconception that VLANs increase network bandwidth. This is false, yet I am still hearing it regularly after 17 years designing networks. I had a customer last year that was installing wireless in a hotel. He decided that giving each room it's own VLAN would both allow each guest to have the full use of the 50 Mbps internet speed and secure each room from being able to access their neighbor's "network". Both assumptions were false, of course, not only do all users still share the same internet bandwidth speed but most modern layer 2/3 switches allow for inter-VLAN routing by default. So his idea of VLAN'ing the entire hotel not only accomplished none of the goals he intended, but he added a ludicrous amount of complexity to the network needlessly. Nearly all managed switches can handle 4094 VLANs, howevevr, if an engineer ever configures even half that many, fire them immediately, please.

New discussion

Ask questions and get answers to your physical security questions from IPVM team members and fellow subscribers.

Newest discussions