Originally posted by marcusBMG Tony Northrup got similar responses. I (and he) never said that the focal length or aperture of the lens changes. I (and he) are saying that if you want to think in terms of full frame equivalence then its both aperture and focal length that need to be multiplied by the crop factor. And the fact is that many do - only yesterday I pm'ed a fellow forum member who had written that a classic 135mm f2.8 would give 200mm!! at f2.8!! And the fact is that many don't appreciate the effect on DoF.
But at the end I agree with Dartmoor Dave that if you don't switch formats you shall just be familiar with the Dof and FoV on the format you use and thats all you in practical terms need - well put mate. But your first comment is just wrong, this is maths not misinformation, and your last comment misses the point: they advertise in terms of full frame equivalence. Bridge cameras are probably the worst offenders - check for yourself. Lenses marked being eg 28-400mm (equivalent) f2.8 except of course they're not! They're 6.5-80mm f2.8 OR 28-400mm f14 (I have assumed 5x CF) described as full frame equivalent.
This is not confusion it is enlightenment.
You - and Tony - are mostly correct.
I say 'mostly' because putting the equivalent aperture right on the lens barrel or camera face does three slightly negative things in addition to the positive things -
1) it doesn't necessarily help anyone's confusion about the subject. I and others have tried to explain equivalence for years now, and even some people who have read the articles, etc are still confused by it and reject it. You can see that by a few responders to this thread. Your average Joe who's just looking at a lens barrel isn't going to do any better than them. (well, he might.
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2) F-stop does affect exposure in a constant way (not Total Light), so it does affect shutter speed in the same way on all formats. Someone primarily concerned with shutter speed, vs. noise, DR, total light and DOF, will thus be confused.
3) It further establishes 135mm (FF) as the 'standard reference'. IMO this isn't
bad - we need some standard so we know what AOV/aperture we're really talking about - but having 35mm be set up as the standard angers a few % of people who shoot smaller formats. This would just rub it in more.
So instead of putting it on the lens, IMO what should happen is *all* professional/commercial review sites and entities should mention the equivalent aperture range for a given combo they review -
like they mention the equivalent FL range now - and commercial sales sites like B&H and Adorama should also always mention it.
Dpreview has started doing this in a graphical way, and good for them (chart below.) IMO this chart is nearly perfect, it tells you much about what you're actually buying in one glance:
Incidentally -->
this is a good, easy article on the subject.
Below is a fantastic practical example of why this is important - look at the Lumix (25-600 f/2.8!!) and Olympus Stylus 1's impressive numbers - and then look again... maybe not so impressive when you know the equivalent aperture range. (and note
yellow highlighted below (from dpreview) :
---------- Post added 10-09-14 at 06:53 PM ----------
Originally posted by JinDesu ....no.... that's not how physics or the sensor works...
A cropped sensor will receive the same quantity of light per area as a larger sensor. The larger sensor will always have more photosites/pixels than the smaller one - so when you look at an equivalent FOV image between a larger and a smaller sensor, the larger sensor has better noise signal when SCALED to an equal pixel count.
I.e. 36MP D800 vs 16MP cropped mode - at 100% crop the noise is the same. You can literally see this in person if you have a D800. You can also see this is true by comparing 100% crops of a D800 to a D7000. The noise at the pixel level is the same in quantity and size. However, upon scaling to equal (whether you scale the 36MP down to 16MP or scale the 16MP up to 36MP), the signal to noise ratio favors the larger sensor.
A larger sensor does not absorb more light than a smaller sensor of the same technology. It just has more pixels/photosites. That's all.
Jin, you have this wrong.
Consider FF sensors that have the same or less pixels than say 16MP - and yet they still show the 1+ stop SNR advantage. Downsampling can't account for those situations.
Here's what's happening in a nutshell - the larger sensor is absorbing more total light
specifically because the physical aperture being used to get the same FOV from the same distance is greater. Understanding this requires that someone understands the basics of equivalence...
Here - two formats, let's assume same sensor efficienncy/generation - same FOV and F-stop and shutter speed (same exposure) :
FF: 70mm f/2.8 = 70 / 2.8 = 25mm physical aperture
m43: 35mm f/2.8 = 35 / 2.8 = 12.5mm physical aperture
So even though they have the same
exposure (light density,) the FF image would have more
Total Light due to twice the physical aperture used to get the same FOV, and thus it would have two stops better SNR, better DR - and also two stops less DOF. This is precisely how FF get's it's noise advantage.
And this ^^ happens independently of # of pixels.
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