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FStops on the Cropped Sensors Not Accurate?


johnortt
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Thanks for all of the replies guys.  I really appreciate everyone's input.

 

On the subject of full frame and comparing it to medium and large format film, I do not think the full frame title is a direct reference to to quality.

 

The only reason why digital cameras didn't just replace the 35mm format in sensor size was the very high cost of the early sensors.

 

Meanwhile the 35mm lenses were used as the professional photographers (who were the only ones who could afford the early digital SLR's) already had a large collection of lenses.

 

To the best of my knowledge all cameras prior to digital made use of the full frame that was available to them - It would be wasteful to build cameras with larger and heavier lenses than were needed.

 

For this reason the reference to full frame is only because it differentiates between the two formats which otherwise look the same.

 

Please feel free to correct me if I have misinterpreted anything.

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  • 2 weeks later...

 

 

These videos clarify the whole "more light" propaganda of FF fanboys...

 

Angry Photographer: FF vs. APSC #1: Debunking "more light" nonsense & brainless filth

https://youtu.be/MW3UOyALsnM

 

Angry Photographer: FF vs. APSC #2: Debunking "more light" nonsense & brainless filth

https://youtu.be/AivLURRVIUU

 

Angry Photographer: FF vs. APSC #3: Debunking "more light" nonsense & brainless filth

https://youtu.be/7o2sm0v0IEg

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Here is how I explain it:

 

When calculating exposure, no correction for sensor size is necessary. The brightness of the image projected by a lens at, say, f/2 is the same regardless of sensor size.

 

If you want to know how your image will compare to an image shot with a full frame camera, multiply both the focal length and the f number by the crop factor. A Fuji has a crop factor of 1.5, so if you are using the 56mm, multiply that by 1.5 and you get 84. The field of view will be the same as an 84mm lens on a full frame camera. (Close enough to 85 that you'll never notice the difference.) If you are at f/1.2, the depth of field will be the same as f/1.8 on full frame.

 

The crop factor is also a good way to compensate for the fact that the smaller sensor gathers less light. At high ISO you can expect to have roughly the same image quality as a full frame camera that has its ISO set one stop lower. You need f/1.2 to get the same high ISO image quality as you would get at f/1.8 on full frame, all else being equal, so that you can set the ISO one stop lower while using the same shutter speed.

 

Put all that together and the 56mm f/1.2 on a Fuji id's like having a very good 85mm f/1.8 on a full frame camera.

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The crop factor is also a good way to compensate for the fact that the smaller sensor gathers less light. At high ISO you can expect to have roughly the same image quality as a full frame camera that has its ISO set one stop lower. You need f/1.2 to get the same high ISO image quality as you would get at f/1.8 on full frame, all else being equal, so that you can set the ISO one stop lower while using the same shutter speed.

 

I don't think this part is correct.

 

It is only correct for sensors of same MP count, because there you have much larger photo cells on the larger sensor. If you compare a 16MP APS-C with a 36MP FF sensor, the photo cells are roughly the same. The noise might be finer when you frame the same photo, but it then depends on a lot of other factors which one is actually better. 

 

And for this:

 

The person you quoted is so stupid, he doesn't know he's stupid.

 

 

Explain where he is wrong. I know one point, but he is actually mostly right, just from a logical and physical perspective.

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I don't think this part is correct.

 

It is only correct for sensors of same MP count, because there you have much larger photo cells on the larger sensor. If you compare a 16MP APS-C with a 36MP FF sensor, the photo cells are roughly the same. The noise might be finer when you frame the same photo, but it then depends on a lot of other factors which one is actually better. 

 

 

Pixel density is largely irrelevant these days. That's why a A7RII isn't that much noisier than a A7SII. Sensor size, OTOH, is relevant, but so is sensor technology. For example, the little APS-C sensor is the Nikon D7200 is clearly superior to any full-frame sensor camera from Canon money can buy. So size (quantity) does matter, but the quality of the sensor is just as important. So it's best to have a large sensor with state-of-the-art ISOless technology, like the Nikon D750 or D810.

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So it's best to have a large sensor with state-of-the-art ISOless technology, like the Nikon D750 or D810.

 

Or go for state-of-the-art non ISOless sensors. Both the A7RII and A7S show, that ISOless can be useful but doesn't automatically mean superior low light performance.

 

Hell - I am not even sure, that the upcoming Fuji sensors will be isoless!

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Or go for state-of-the-art non ISOless sensors. Both the A7RII and A7S show, that ISOless can be useful but doesn't automatically mean superior low light performance.

 

Those sensors are pretty much ISOless, too, as all current Sony sensors are. But Sony seems to do some processing that either degrades the push (was definitely the case with their compressed RAWs) or further improves the analog push. Makes sense with the A7SII and very high ISOs, where even low read noise becomes an issue and can be reduced by applying analog gain of 2-3 stops first. Plus, there's more to an image than just the sensor. Luckily, Nikon has the ISOless game well covered. 

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about ISOless (hate that word ). Sure, Canons are ISOless too at some point. The interesting thing about Dual Gain is, that it behaves like "two stage isoless"

 

And looking at Sony cameras that use the same sensor as others do,  I would love to see Nikons (or Fujis) go on this.

 

 

about the "knowing soon enough". Christmas is coming (Winter not yet), but the real christmas seems to come in January.

 

All the small things rumoured about the X-Pro2 sound really interesting, let's see if that goes for the sensor too

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