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10-09-2014, 06:31 AM   #16
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There's a part 3 rebuttal video.

10-09-2014, 09:05 AM   #17
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QuoteOriginally posted by promacjoe Quote
First of all, ISO does mean something, International Standards Organization.
International Organization for Standardization. This organization sets the standards for Light capacity of film and digital cameras.
the ISO value for film dates back to 1942 (revised later in 1943 to 1947) at that time the organisation was still called ANSI (later in 1947 became the ISO - because it was international and not only american).

Before, it was express in national value - DIN in germany, ASA in France, BSI for the british, GOST for the Russia.

So the guy is basically right, the name "ISO" is not really related to the ISO organisation name. And by the way the real name is not "ISO" only but "exposure value ISO" because internationaly equalized (equivalent - hence ""ISO" from greek"deduction, i guess) to be able to convert DIN / BSI / ASA / GOST exposure value to unique ISO exposure value.
10-09-2014, 12:24 PM   #18
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QuoteOriginally posted by aurele Quote
the ISO value for film dates back to 1942 (revised later in 1943 to 1947) at that time the organisation was still called ANSI (later in 1947 became the ISO - because it was international and not only american).

Before, it was express in national value - DIN in germany, ASA in France, BSI for the british, GOST for the Russia.

So the guy is basically right, the name "ISO" is not really related to the ISO organisation name. And by the way the real name is not "ISO" only but "exposure value ISO" because internationaly equalized (equivalent - hence ""ISO" from greek"deduction, i guess) to be able to convert DIN / BSI / ASA / GOST exposure value to unique ISO exposure value.
Go to this webpage .iso.org/iso/home.html , And tell that to them. that their official Logo doesn't mean anything. This organization produces standards for more than just film. Anything that needs a standard is certified by this organization. Weights, measurements, screw threads.

And by the way, I know the history of the organization and the standards that were implemented for photography, Along with many other standards that were implemented by this organization.

The ISO organization establishes standards for many other industrial and nonindustrial products. I have been dealing with these standards for over 40 years. And it does mean something. It means when you go into a hardware store, to buy a bolt it will fit your application. Everything from wire to plumbing fittings, even the oil in your car has an ISO standard. Without these standards it would be impossible to do business with other countries. Before standards were established, in this country every Company had their own standards for screw threads. You could not go into a hardware store and buy a bolt, and be assured that it would fit your application. It had to be custom-made. Something we take for granted now.

Thousands of years ago every country had their own unit of measurement. One kingdom imported Masons and other skilled labor From other countries and quickly found out that each was using their own unit of measurement. They quickly realized that they had to establish a uniform standard to get anything done. They created a Rosetta Stone of standards, So to speak. The first known standards that ever existed.

They needed them then, and we need them now. ISO is definitely not just a word. It is a set of standards that most of the world follow.
10-09-2014, 01:09 PM   #19
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Can someone explain why some of you are so upset with the video? I have read the posts but do not get it. I think the video was informative and the math sound.

10-09-2014, 02:18 PM   #20
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QuoteOriginally posted by promacjoe Quote
Go to this webpage .iso.org/iso/home.html , And tell that to them. that their official Logo doesn't mean anything. This organization produces standards for more than just film. Anything that needs a standard is certified by this organization. Weights, measurements, screw threads.

And by the way, I know the history of the organization and the standards that were implemented for photography, Along with many other standards that were implemented by this organization.

The ISO organization establishes standards for many other industrial and nonindustrial products. I have been dealing with these standards for over 40 years. And it does mean something. It means when you go into a hardware store, to buy a bolt it will fit your application. Everything from wire to plumbing fittings, even the oil in your car has an ISO standard. Without these standards it would be impossible to do business with other countries. Before standards were established, in this country every Company had their own standards for screw threads. You could not go into a hardware store and buy a bolt, and be assured that it would fit your application. It had to be custom-made. Something we take for granted now.

Thousands of years ago every country had their own unit of measurement. One kingdom imported Masons and other skilled labor From other countries and quickly found out that each was using their own unit of measurement. They quickly realized that they had to establish a uniform standard to get anything done. They created a Rosetta Stone of standards, So to speak. The first known standards that ever existed.

They needed them then, and we need them now. ISO is definitely not just a word. It is a set of standards that most of the world follow.
you just didn't read what i wrote : basicaly the universal "ISO exposure values" were created BEFORE the ANSI became the ISO organisation. Period.
This "ISO exposure value" is just an example that show why the ANSI (that was only US) needed to become more international and not only american.

So YES, the "ISO exposure value" existed BEFORE the ISO organisation was created, or if you prefer change name from ANSI to ISO organisation.

I never said anything else regarding the ISO organisation, so don't start your long litany with a small tint of wickedness hidden behind a touch of politeness, thank you very much.

BTW : beside that, don't worry, i didn't take that as an offence.
10-09-2014, 04:14 PM   #21
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QuoteOriginally posted by aurele Quote
you just didn't read what i wrote : basicaly the universal "ISO exposure values" were created BEFORE the ANSI became the ISO organisation. Period.
This "ISO exposure value" is just an example that show why the ANSI (that was only US) needed to become more international and not only american.

So YES, the "ISO exposure value" existed BEFORE the ISO organisation was created, or if you prefer change name from ANSI to ISO organisation.

I never said anything else regarding the ISO organisation, so don't start your long litany with a small tint of wickedness hidden behind a touch of politeness, thank you very much.

BTW : beside that, don't worry, i didn't take that as an offence.
my post was not meant to be anything but informative. the ISO rating for film is based on the ANSA/DIN standards. it is based on previous work done with those standards as is most international standards. ISO means that it has been adopted by the international standard organization. And as a standard, all film/digital medium should adhere to that standard. Without these standards, We would be back in the 1700s, where there was a photographic store pretty much on every corner but you could not go by a photographic plate from one vendor and get the same results as you got from another vendor. With the ISO standard, you can pick up pretty much any camera, from any country, and get the same results, using the same ISO rating, f-stop and shutter speed, and you no longer have to translate the film speed when you are in a different country. that is why it means something.



As far as why this video bothers me, and I can only speak for myself, I guess I have just seen too many people trying to disguise a sales promotion is a tutorial. And when they start out with bad information, well, I just get tired of It.

We need good reliable and consistent information. Not people putting their own spin on the information.
10-10-2014, 12:40 AM   #22
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QuoteOriginally posted by promacjoe Quote
my post was not meant to be anything but informative. the ISO rating for film is based on the ANSA/DIN standards. it is based on previous work done with those standards as is most international standards. ISO means that it has been adopted by the international standard organization. And as a standard, all film/digital medium should adhere to that standard. Without these standards, We would be back in the 1700s, where there was a photographic store pretty much on every corner but you could not go by a photographic plate from one vendor and get the same results as you got from another vendor. With the ISO standard, you can pick up pretty much any camera, from any country, and get the same results, using the same ISO rating, f-stop and shutter speed, and you no longer have to translate the film speed when you are in a different country. that is why it means something.
i've never pronouce anything against that.

A simple misunderstanding from both parts, i guess.

Let's move on, and take picture
10-18-2014, 03:46 AM   #23
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QuoteOriginally posted by dtmateojr Quote
ROFL! Waste of time! I stopped when he mentioned that different formats have different ISO calibrations!!! ROFL!!! What an idiot!

The same film emulsion is available in different formats. End of story.
ISO is an output format standard. It has absolutely nothing to do with image sensor tehhcnology, diffraction or sensor format.

  1. Anyhow, let us consider two sensors created with similar technology, FF - a full crame, and C2, a crop factor 2 sensor.
  2. Let's used fixed aperture of f/2
  3. Let's have exposure time of 1 second
  4. The FF collects four (4) times more photons (ie. particles of light) than the C2
  5. The SNR of the FF image is twice thaf the C2 image
  6. If the field of view is same, then the FF has more shallow DOF
  1. If instead we were to use f/4 for the FF insead of f/2:
  2. The images would be identical
  3. However - the C2 sensor would reach the saturation point earlier
  4. Thus FF sensor culd be exposure for four (4) times longer
  5. If that were done, the SNR advantage of it would be restored to factor of 2.


These are scientific and mathematical facts.
Can you argue them without insults?

10-20-2014, 01:18 PM   #24
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QuoteOriginally posted by Winder Quote
An 82.5mm F/1.4 lens would have an aperture area of 2727.3 mm^2
The 55mm F/1.4 lens has an aperture area of 1211.81 mm^2.

The aperture on a 55mm lens would need to be F/1.0 in order for it to equal the 82.5mm F/1.4 in terms of quantity of light projected on the sensor.

The area of aperture on an 82.5mm F/1.4 lens would be 2.25x larger than the 55mm F/1.4. At F/1.4 the 55mm does not project as much light onto the sensor as the 82.5mm lens. Pentax compensates for this by applying more digital amplification so that all settings being equal they produce images of the same level of brightness.
The f number is not actually related to the front aperture, but to the aperture stop. Often the front element is the aperture stop, or a good approximation of it, but you cannot just measure the front element and use that value.

That video is full of wrong, inaccurate and simplified "information". ask any lens designer to get your facts right
10-20-2014, 06:09 PM   #25
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QuoteOriginally posted by bdery Quote
The f number is not actually related to the front aperture, but to the aperture stop. Often the front element is the aperture stop, or a good approximation of it, but you cannot just measure the front element and use that value.

That video is full of wrong, inaccurate and simplified "information". ask any lens designer to get your facts right
I have wondered about that, the general formula works for most lenses using the front element diameter, but for some lenses (like the Sigma 35mm F1.4) it doesn't. Can you point to some good explanation of what is meant by 'aperture stop'?

John.
10-20-2014, 07:36 PM - 1 Like   #26
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On most lenses often just behind the object lens, there is a aperture block that limits the f-Number. This aperture block reduces unwanted stray light that comes into the lens. Because of this aperture block, Even though the actual diameter of the lens is close, the actual diameter of the lens should not be used to determine light capacity of the lens.
10-21-2014, 05:42 AM   #27
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QuoteOriginally posted by jhmos Quote
I have wondered about that, the general formula works for most lenses using the front element diameter, but for some lenses (like the Sigma 35mm F1.4) it doesn't. Can you point to some good explanation of what is meant by 'aperture stop'?
QuoteOriginally posted by promacjoe Quote
On most lenses often just behind the object lens, there is a aperture block that limits the f-Number. This aperture block reduces unwanted stray light that comes into the lens. Because of this aperture block, Even though the actual diameter of the lens is close, the actual diameter of the lens should not be used to determine light capacity of the lens.
There you go. The aperture stop, in other words, is the plane where the light path is the most constrained.

Sometimes the aperture stop is at the iris, because it's often convenient, and it often is where the light path diameter is the smallest. But following the light rays' paths, you can create a virtual aperture stop at any point on the light path. The front element is often quite well matched with this, in order to avoid using more glass than what is necessary, but it's never a perfect match.
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