DOF and Cropping take 2

Started 8 months ago | Discussions thread
justin23
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Re: U R Slippery II
In reply to awaldram, 8 months ago

awaldram wrote:

Ian Stuart Forsyth wrote:

awaldram wrote:

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

You just proved why it shouldn't be under exposed with your answer here kind of

http://www.dpreview.com/forums/post/53107658

Yep but thats obvious iso 100 = iso 100 on any format , f2.8 = f.28 , 1/180 = 1/180 format is irrelevant there a constant.

Hence my bewilderment about your claims to the contrary.

So irrelevant of sensor efficiency or size (light density) a camera will have the same exposure solution for the same ISO set.

the Q at F/2.8 1/80 iso 800 needs more gain as it has captured 13 times less total light than K3 at F/2.8 1/80 iso 800 because of the sensor size difference

Not sure what you trying to say. the Q will produce more noise at iso 800 than the k3 because it requires more internal gain to match sensitivity but both will have the same light sensitivity at iso800.

We can reduce the AP on the K3 to F/10 raise the iso 3000 and then it would gather around the same total light as the Q F/2.8 1/80 iso 800

Why would you do this.?

Or another way to look at it the Q iso 800 = k3 iso 3000

No chance ISo is a standard its calibrated and set on every camera ever made , without it photography would not exist as it does today. Every camera would require custom algorithms for every exposure

Q iso800 = k3 iso 800 = 645d iso80 = glass plate camera iso800 = hubble telescope iso800.

As the image I posted proved setting the same aperture , the same shutter and the same iso results in the same exposure across formats.

Not sure what your showing maybe that the k3 noise at 3200 is similar to Q7 @800?

I could only find the Q7 to compare to the K3

What you are really comparing is relative noise. Yes ISO 800 on smaller sensors is likely to have more noise and may have similar noise to a K-3 ISO 3200, but if you take a photo on a K3 at say iso 800 f8 and 1/250 you will use the same settings on a Q for the same exposure. In fact the sensor pitch is more important, because on a per area basis they'll all get the same amount of light, its just how well the sensor can capture it, a bigger sensor with the same sensor pitch as a smaller sensor captures the same amount of light per area and should be close on noise.

However the smaller sensor tend to have a much higher pitch and thus the noise is higher.  What amuses me most is the only reason we don't have FF sensors with such a high pitch is cost and the smallish market.

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Justin
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