Originally posted by dtmateojr If you only care about DoF then you will feel that way. A f/2 is a f/2 in terms of light and to real photographers that's what matters the most. I don't think you can buy a 70-200 f/2 full frame at all.
f/2 is f/2 in terms of light density, not the total amount of light collected.
f/2 on different formats turns out different image - a cell phone camera at f/2 captures little light, thus also hase deep depth of field, while an APS-C with the same field of view has much more shallow DOF and also captures much more light and a FF captures still more light and has more shallow DOF.
If the field of view, shutter speed and aperture number remain the same, then the bigger the sensor, the more shallow the DOF and the more the sensor collects and the better the signal-to-noise ratio of the image will be.
---------- Post added 18-10-14 at 13:16 ----------
Originally posted by dtmateojr So why compare f/2 and f/4? That's two stops of difference.
And be more specific and say you care only about shallow DoF
f/2 on one format equals f/4 on a different format.
Lets consider idealised systems - a perfect lenses and perfect image sensors. Let's compare two systems:
- Full frame (FF)
- Crop with crop factor of 2 (C2)
For the same field of view (ie. FF with twice the focal length) if the FF has twice the aperture number than the C2 has, the images the cameras will create will be identical. The same noise, the same DOF.
If you use the same exposure settings, then FF image will have more shallow DOF, but also signal to noise ratio twice as good, thus much less noise.
---------- Post added 18-10-14 at 13:19 ----------
Originally posted by dtmateojr Anyone interested in factual content should avoid that site.
Equivalence as defined by for example Great Bustard of DPR forums is very real tool consistent with the laws of physics.
---------- Post added 18-10-14 at 13:24 ----------
Originally posted by dtmateojr Ask the mods. They "featured" an article that was purely wrong and stupid and they didn't want them to be exposed. Have a read on that article and see how many photographers are mocking it.
Can you defend your equivalence-fu or are you no different to the other fauxtogs in dpreview?
The reason why you were banned was your extraordinary impolitelness. You were very rude and kept on insulting people. It had nothing to due with your arguments.
Do you seriously think that you were banned because of your "secret knowledge" which should not be posted on DPR-forums because it would embarrass DPR in some way?
---------- Post added 18-10-14 at 13:32 ----------
Originally posted by dtmateojr Then you do not understand f-stop at all. If you do not understand f-stop then you do not understand exposure. Ergo you do not understand photography.
For the record, aperture is NOT THE SAME as f-stop. Aperture by itself does not explain exposure. You are completely ignoring the effect of focal length. I will not attempt to educate you further. You are very deep down the equivalence-fu rabbit hole like that guy sherman. Getting out of that trap is worse than changing religion. I advise you to stay where you are and continue believing the BS.
This is precicely the kind of language that got you banned from DPR. It is hard to imagine you'll be tolerated here for long either if you keep this up.
Anyhow, regarding equivalancy:
- If one captures twice the light, the signal doubles and the noise increases by factor of sqrt(2). This is basic physical fact that comes from the quantum mechanical nature of light - it's probability function collapse obeys poisson distribution.
- It doesn't matter how you capture the extra light - it may be captured by having a larger aperture (not aperture number, but the diameter of aperture) or by exposing longer
- For any field of view the bigger sensor requires longer focal length, thus as aperture diameter is f/#, ie. focal length divided by aperture number, more light will be collected if the aperture number is the same.
If you want to combat equivalency, you should involve the mathematics of SNR to it - unfortunately those don't support your position so I'm not expecting them to appear.
---------- Post added 18-10-14 at 13:55 ----------
Originally posted by dtmateojr So where did I say that f-stop is dependent on sensor size? In fact, I have stated exactly that f/2 is f/2 regardless of format.
---------- Post added 10-07-14 at 19:01 ----------
It's really funny 'coz a lot of fauxtogs here say that I'm wrong and yet they can't even provide any counter-arguments.
The problem is that you don't read or consider the the counter arguements. After a while no one bothers to counter you as you keep repeating your ever unchanging message regardless of it's factual incorrectness.
Like the f/2 is f/2 regardless of format. Please take a picture with a cell phone at f/2 and then with your "real camera" an image with the same field of view, and tell me if the f/2 on that gives the same DOF and SNR or not?
It is trivial for you to test your hypothesis, but you don't do it but rely on your reasoning inspite the evidence contradicts it.
If you only have one camera, then do this (adapt according to your lens lineup): take picture at 25mm and f/2 and a picture at 100mm and f/2. Crop the 25mm image to match the FOV of the 100mm (to simulate a crop-factor). Then present the images at the same size and analyze the results and tell us what you see. Please do this. We might all learn something.