Sigma 18-35mm f/1.8 FX equivalent

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

Serjojeee wrote:

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).

Nope, DoF not only relates to F stop but also to the distance from the subject. The closer you are the narrower the DoF is.

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.

Approach any Pro and tell this to them.

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.

I read that on many different sites and laugh my ass off.

Not only reading but making some actual calculations helps to understand a pretty simple idea of equivalency.

Like I asked you before, do you calculate or take pictures?

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.

That is not how it works. If it worked like that then I could just crank ISO and shoot at high speed all the time. I would not have to worry about fast lenses or the sensor. Math sure works but in real life math does not always complies with reality. Just not that simple.

Also, you can't take the same picture from any camera ever produced. Small sensor camera have larger DoF by design. Just one example. You can't freeze wings of the humming bird unless you have high speed shutter which I am not sure if any DSLR has these days. Nikon D1 used to have 1/16000. And so on and on. So stop BSing and go shoot some pictures.

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