Sigma 18-35mm f/1.8 FX equivalent

Started 9 months ago | Discussions thread
Serjojeee Senior Member • Posts: 1,306
Re: A perfect proof......

SushiEater wrote:

Serjojeee wrote:

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.

I think that you sometimes just can't explain the equivalence to a person who is not that good at mathematics (he can be a brilliant photographer of course). But I agree that equivalence is about one thing - the actual amount of photons that will hit the sensor (or any other device from film to asphalt) that relates to SNR. And some people don't realize that not only DOF / F stop but also shutter speed AND ISO are a part of equivalence idea cause with different sensor sizes you need the different actual power of light and different exposure time to have the same SNR. The goal is to collect exactly the same number of photons within the specified amount of time. So to get the same picture you'll need to know 2 things - desired DOF and desired SNR. And than you can use everything from smartphone to medium format camera with all cameras en-between to get exactly the same picture (smartphone cameras will limit you with their F18 lenses). But I really don't want to participate in this holy war.

Do you do the calculations of DOF and SNR while you are shooting?

You don't need that. I just describe equivalency this way.

The only way you can influence DOF

DOF relates to F stop (with equivalency in mind).

is if you are shooting portrait on tripod and your model is not moving. But in reality can you really tell the difference between F4 and F5.6 while shooting. No one can. And if you are wide open with wide lenses it is even more difficult.

And please don't start me on SNR.

The bottom line here is that this conversation is really for amateur gearheads and nothing to do with the actual photography.

We are talking about basic photography mathematics. IMO all photographers must know that. But some people don't think so and I'm OK with that. IMHO instead of arguing you can spend your time more beneficial and read the article about equivalency and noise on this site. Not only reading but making some actual calculations helps to understand a pretty simple idea of equivalency. There are only 3 things to change in photography - exposure time, aperture size and sensitivity of light gathering device. And with equivalency in mind you can get the same picture from any camera ever produced. But the whole idea of equivalency is about getting the same amount of photons within a specified time interval with totally different instruments.

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