December 11, 2017, 06:22:20 AM

Author Topic: Canon PowerShot G1 X Mark III Coming Mid October [CR3]  (Read 13696 times)

stevelee

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #45 on: September 22, 2017, 06:43:07 PM »
Explain to me how a lens at f/7.6 lets in the same amount of light as at f/2.8.

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #45 on: September 22, 2017, 06:43:07 PM »

privatebydesign

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #46 on: September 22, 2017, 07:12:50 PM »
Explain to me how a lens at f/7.6 lets in the same amount of light as at f/2.8.

That's easy.

Take an 8mm f2.8 lens = aperture opening of 8/2.8 = 3.6 mm aperture opening.
Take a 27mm lens set to f7.6 = aperture opening of 27/7.6 = 3.6 mm aperture opening.

They are the same sized hole so they let the same amount of light in.

« Last Edit: September 22, 2017, 07:28:24 PM by privatebydesign »
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

okaro

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #47 on: September 23, 2017, 06:31:18 AM »
Explain to me how a lens at f/7.6 lets in the same amount of light as at f/2.8.

That's easy.

Take an 8mm f2.8 lens = aperture opening of 8/2.8 = 3.6 mm aperture opening.
Take a 27mm lens set to f7.6 = aperture opening of 27/7.6 = 3.6 mm aperture opening.

They are the same sized hole so they let the same amount of light in.

Assuming they gather that light from same angle.

stevelee

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #48 on: September 23, 2017, 09:38:14 AM »
I’m still confused. If it is the same amount of light, why does the camera consider it a different exposure?

Even with the same lens and lens opening you don’t always get the same amount of light, such as with extension tubes.

privatebydesign

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #49 on: September 23, 2017, 10:03:52 AM »
Explain to me how a lens at f/7.6 lets in the same amount of light as at f/2.8.

That's easy.

Take an 8mm f2.8 lens = aperture opening of 8/2.8 = 3.6 mm aperture opening.
Take a 27mm lens set to f7.6 = aperture opening of 27/7.6 = 3.6 mm aperture opening.

They are the same sized hole so they let the same amount of light in.

Assuming they gather that light from same angle.
No, the aperture is at the focal point of the objective in a simple lens, the light path in a complicated one, so the angle of the light is not that relevant. Same hole size, same amount of light.

I’m still confused. If it is the same amount of light, why does the camera consider it a different exposure?

Even with the same lens and lens opening you don’t always get the same amount of light, such as with extension tubes.

Because the sensors are a different size so each section of sensor by area takes the same amount of time to receive the same amount of light. Ergo, if your sensor is twice as large it will take twice as long to get the same amount of light per area.

 But that isn’t the end of it, iso, or sensor sensitivity, means that if you double the sensitivity you get the ‘same’ end result from twice the sensor area, in reality you get a touch more.

So if you use that 8mm lens at f2.8 and the 27mm at f7.6 on two cameras with equivalent sized sensors ( such that the fov from both is the same) you will get the same noise characteristics from both at compensated iso values. So to get two ‘identical images’ from two systems whereby identical mean same fov, dof, noise, shutter speed (for subject movement) etc etc when printed or viewed at the same size from the same place you’d use these camera settings.

8mm f2.8, iso 100, 1/60 sec.
27mm f7.6, iso 1000, 1/60 sec.

These settings will give you equivalent pictures from different sized sensors. To get the definite article on all this read here. http://www.josephjamesphotography.com/equivalence/
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

privatebydesign

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #50 on: September 23, 2017, 10:13:56 AM »
P.s. don’t start introducing complex things like extension tubes into the mix, they can be explained, but are just side issues.

An extension tube effectively changes the focal length of the lens, as does focusing closer than infinity but the differences are so small at greater than macro magnifications as to not mess with the basic equations enough to make a visible difference, there fore the focal length/aperture relationship changes so the equivalence calculation changes. It’s all explained much more thoroughly in the linked article.
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

stevelee

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #51 on: September 23, 2017, 11:22:11 AM »
OK I follow a lot of that and have said some of the same things myself in this forum. It does seem that the article uses some sleight of hand in saying that there is less exposure on a larger sensor because you have the same light spread over a larger area, and then the more intuitive idea that a crop sensor will get less light since it occupies a smaller part of the circle of light coming from the lens. But if I spend more time with the article, I can probably sort out what he means by the apparent contradiction.

But I don’t follow at all how it is meaningful to say it is the same amount of light when one requires ISO 100 and the other ISO 1000.

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #51 on: September 23, 2017, 11:22:11 AM »

okaro

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #52 on: September 23, 2017, 05:21:55 PM »

Assuming they gather that light from same angle.
No, the aperture is at the focal point of the objective in a simple lens, the light path in a complicated one, so the angle of the light is not that relevant. Same hole size, same amount of light.

Totally incorrect. A wide angle lens gathers much more light from same size of aperture. Think about aperture of 10 mm. That could be a 20 mm wide angle at f/2 or a 160 mm Tele at f/16. The former gathers much more light.

okaro

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #53 on: September 23, 2017, 05:27:26 PM »
I’m still confused. If it is the same amount of light, why does the camera consider it a different exposure?

Even with the same lens and lens opening you don’t always get the same amount of light, such as with extension tubes.

Exposure is determined by light per square area of the sensor. If the light is spread to a larger sensor then one needs a higher ISO for the light to produce correct image. Of course the larger sensor can tolerate that so the overall image qualify is same.


privatebydesign

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #54 on: September 23, 2017, 05:48:04 PM »

Assuming they gather that light from same angle.
No, the aperture is at the focal point of the objective in a simple lens, the light path in a complicated one, so the angle of the light is not that relevant. Same hole size, same amount of light.

Totally incorrect. A wide angle lens gathers much more light from same size of aperture. Think about aperture of 10 mm. That could be a 20 mm wide angle at f/2 or a 160 mm Tele at f/16. The former gathers much more light.

Not when talking about it in relation to equivalence, which we were and in retrospect I don't make clear in my followup answer. When talking about equivalence the fov from the different focal lengths is the same, so the angle of light captured is the same.
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

stevelee

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #55 on: September 23, 2017, 05:50:13 PM »
I’m still confused. If it is the same amount of light, why does the camera consider it a different exposure?

Even with the same lens and lens opening you don’t always get the same amount of light, such as with extension tubes.

Exposure is determined by light per square area of the sensor. If the light is spread to a larger sensor then one needs a higher ISO for the light to produce correct image. Of course the larger sensor can tolerate that so the overall image qualify is same.

Except that the larger sensor covers more of the circle of light that the lens projects, and a smaller sensor covers a smaller portion of it.

pokerz

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #56 on: October 13, 2017, 07:03:26 AM »
Explain to me how a lens at f/7.6 lets in the same amount of light as at f/2.8.

To achieve F2.8 in wide end, Canon's trick maybe here (has been implemented in G7x, G1x)  :)

Archbob

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #57 on: December 07, 2017, 04:33:53 PM »
So I have one of these on my desk right now for testing and review right now and I can't seem to open the RAW files in anything. The Adobe DNG converter won't convert them and I can't open them in the latest version of photoshop or view them.

What do you guys use to process these RAW files?

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Re: Canon PowerShot G1 X Mark III Coming Mid October [CR3]
« Reply #57 on: December 07, 2017, 04:33:53 PM »