Changing aspect ratio confuses the issue. We need to get mamallama to step zero before we can move to step one.
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Lee Jay
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A beginner's guide to "is equal to" vs "is equivalent to".
- Thread starter Great Bustard
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Lee Jay
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tko
Veteran Member
Actually, equivalence is vastly underrated. "Equivalence" theory shows which lenses have equal performance. "Equivalent lenses" have similar size, weight, DOF, and resolution. Oh, not to the last decimal point, but as good as you're going to get.
Compare that to lenses with the same F-stop. They can have widely different sizes, weights, DOF, and resolution. Saying a F/2.8 lens on a cell phone has any resemblance to F/2.8 on a crop, medium format, or a telescope is a joke. The only thing they have that is similar is exposure--which has nothing to do with photographic quality or properties.
Remember, the F-stop is itself a parameter that has been normalized to the sensor size as an aid to set exposure manually. Aside from that, it's useless. Equivalence theory really de-normalizes the F-stop so that you can compare the true properties of a lens.
Compare that to lenses with the same F-stop. They can have widely different sizes, weights, DOF, and resolution. Saying a F/2.8 lens on a cell phone has any resemblance to F/2.8 on a crop, medium format, or a telescope is a joke. The only thing they have that is similar is exposure--which has nothing to do with photographic quality or properties.
Remember, the F-stop is itself a parameter that has been normalized to the sensor size as an aid to set exposure manually. Aside from that, it's useless. Equivalence theory really de-normalizes the F-stop so that you can compare the true properties of a lens.
Moti
Veteran Member
In theory that looks convincing but on a practical plan, depending on what you are photographing, it doesn't always work like this.
I'm a pro concert photographer shooting mainly classic concerts so you can understand that low light is my daily bread. When I shoot a full orchestra on stage, my main concerns are shutter speed high enough to avoid motion blur, and DOF deep enough to get the whole orchestra in focus.
I shoot mainly M4/3 so let's assume that in an average concert hall lighting I can shoot at f/2.8 and still have enough DOF to get everyone in focus, and ISO 800 would get me the shutter speed needed to eliminate motion blur.
If I would have used a FF camera instead, for the same DOF I'd have to shoot at f/5.6 and then in order to maintain my shutter speed I'll have to boost up ISO to 3200. And this is how the FF two stops theoretical noise advantage flies out of the window.
of course, this is a specific case but I mentioned it because in real world photography, things do not always behave as they are in theory.
Moti
Great Bustard
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...that's exactly what the theory says. What about the above do you feel differs from the theory?
Moti
Veteran Member
In a way yes because in many debates here, the theory doesn't take into acccount different situation of real world photography. Everybody will tell you that a FF sensor has two stops noise advantage compared to a 4/3 cropped sensor, which is not in my specific case.
Moti
Michael Fryd
Veteran Member
The issue is that the "full frame advantage" isn't what most people think.
Assuming your shutter speed is constrained, similar sensor technology, and the same angle of view; low light performance is generally a function of depth of field. This is independent of sensor size.
As you have noticed, at the same angle of view and same shutter speed, your full frame camera needs a 2 stop higher ISO in order to get the same image as a 2X crop body.
The real advantage of larger sensors, is that for a given angle of view, you generally have the option of a larger aperture diameter. That larger aperture diameter gives you both better low light performance, and shallower depth of field.
If you are in a position where you can tolerate that shallower depth of field, the larger sensor gives you that option. In a situation like yours, where you can't tolerate shallower depth of field, there isn't an advantage to moving to a larger sensor.
This isn't to say that full frame is "better". it simply means that full frame offers more options. If you need/want those options, then there is an advantage to the larger sensor. If you don't need the option, than there's no advantage to a larger sensor.
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For instance, I have a 50mm f/1.8 lens for my full frame camera. This is a common and inexpensive lens. Wide open it yields a shallow depth of field and reasonable low light performance.
On a 2X crop body, I would a 25mm f/0.9 lens in order to match that shallow depth of field and associated low light performance. That's not nearly as common a lens.
My local Best Buy has in stock a 50mm f/1.4 or a 50mm f/1.2 lens for my camera. A 2X crop body would need a 25mm f/0.7 or f/0.6 in order to match that depth of field.
If you seldom shoot 50mm wider than f/5.6, then you can shoot your 2X crop with a 25mm at f/2.8. If that's your shooting style, you won't benefit from a full frame.
Unless you need/want to shoot with shallower depth of field, there isn't a significant advantage to larger sensors.
Michael Fryd
Veteran Member
The 2 stop noise advantage is only available if you are willing to accept 2 stops shallower depth of field. If you are depth of field limited, then there is no significant advantage to the larger sensor.
Those who suggest otherwise may not fully understand the situation.
Moti
Veteran Member
Exactly, but if you understand my needs, you can see that my situation is just the opposite. I need deep DOF and not shallow DOF and therefore a FF sensor does not represent much of an advantage to my photography.
Moti
Mackiesback
Veteran Member
Do you feel the noise on a full frame sensor at 3200 iso is the same as noise on a 4/3rds at 3200? Or maybe the noise ff at 3200 is more like 800 on 4/3rds?
kiwi2
Veteran Member
Sure, people can express mathematical equations to explain something.
It doesn't mean other people have to think it's that terribly important to the outcome of their photography work.
Great Bustard
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One needs to distinguish between what the theory says, and what "everyone" says. For example, the theory does not say, for example, that an f/1.4 lens on mFT "really is" f/2.8 -- it says that f/1.4 on mFT is *equivalent* to f/2.8 on FF. Likewise, with your example, when "everybody" says that FF has a two stop noise advantage over mFT, the implication is that this is for the same exposure and equally efficient sensors.
So, rather than say that "things do not always behave as they are in theory", better to say that the theory has conditions that are not always spelled out (and, when spelled out, those doing the spelling out often get accused of being "overly pedantic" and "repetitive", so it's a damned if you do, damned if you don't situation).
ttran88
Veteran Member
I thought photography was supposed to be fun!
When I step forward with my right foot, I can't ignore that the next will necessarily be with my left, but I still have to put my right foot down first.
Dealing with that is the next step. Let's get this straight without an aspect ratio change first.
Iliah Borg
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Higher ISO setting doesn't increase noise. Lower exposure does.
Great Bustard
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Why should it not be? Skydiving is fun, too, whether or not you care about or understand gravity.
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Great Bustard
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Sure. You don't need to understand gravity to enjoy (and be good at) skydiving. But you wouldn't argue against gravity would you? And you wouldn't say that someone computing how much time you have before you hit the ground in the event of a chute malfunction is full of it, would you?
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Iliah Borg
Veteran Member
The more I read this thread the more I doubt your numbers ~<True, but for DPR, most of the members that are participating know what a poster discussing APS-C to FF, etc, know what that poster is talking about.
But to stop any additional thread drift, I reduce my '99.9%' to 83%.
David
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Michael Fryd
Veteran Member
Correct. There is no advantage to a larger sensor unless you can tolerate shallower depth of field. For someone in your situation, who can't tolerate shallower depth of field, there is no significant advantage to a larger sensor.
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