Sigma 18-35mm f/1.8 FX equivalent

Started 9 months ago | Discussions thread
SushiEater
SushiEater Forum Pro • Posts: 11,356
Re: A perfect proof......

MediaArchivist wrote:

SushiEater wrote:

Also, before someone puts in their $.02 I don't care about DOF.

So your "wrong wrong and wrong" statement was not about facts, but was about how things fit (or don't fit) into your whims and tastes. You should make that clear.

No, my statement was about this:

"18-35mm f1.8 lens on APS-C is like a 27-53mm f2.8 lens on FF."

On APS-C 18-35mm F1.8 lens Nikon mount that is is 27-53mm F1.8 which I have proven with my photo samples. On FF camera shutter speed is 1/60, on Crop camera my shutter speed 1/160 that is why it allows me to shoot at the higher speed. You can't beat the math that brighter lens allow for higher shutter speed no matter how conniving and twisting you are getting.

Furthermore from the link you should not have provided because it is working against you:

"The F-number itself doesn't change with sensor size, just as actual focal length doesn't change with sensor size. However, the situation is essentially the same as with equivalent focal lengths: put a 50mm lens in front of a smaller-than-full-frame sensor and it's still a 50mm lens, but you get a narrower angle-of-view, because you're not capturing the full extent of the circle-of-light the lens is projecting. So we might say the lens is now 'acting as a 100mm equivalent' lens.

In a similar way, the actual F-number always tells you the intensity of the light on each square mm of the sensor - this doesn't change with sensor size. By comparison, the equivalent aperture takes into account how many square mm of sensor you've put behind the lens."

Basically what it means is that even though 4/3 camera receives 4x less light it will shoot with the same shutter speed as the FF camera if you put equivalent lens on both cameras.

If you disagree with that you are disagreeing with the article YOU posted.

And this:

"The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity."

Basically what it means is that even though 4/3 camera receives 4x less light it will shoot with the same shutter speed as the FF camera if you put equivalent lens on both cameras and use the same ISO.

If you disagree with that you are disagreeing with the article YOU posted.

But as I said before ISO does not concern me as long as I shoot at acceptable ISO and DOF concerns me even less because it depends on the distance and frankly no one cares if it is F1.8 or f2.8 or even F5.6. What agency does care is that the image I create is sharp, properly exposed and without blur. And the only way to achieve that is to use sharp, bright lens at higher shutter speed.

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