There is no magical size/weight advantage

Started Mar 5, 2014 | Discussions thread
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Re: There is no magical size/weight advantage
In reply to razormac, Mar 8, 2014

razormac wrote:

I should probably just shut up since I can see I am only wasting my time, but I will call one final witness:

Nikon 1 10-30mm f3.5-5.6 vs Sigma 1-20mm f4.0-5.6

N1 10-30mm (2.3x1.7in) and 116g (4.1 oz)

Sigma 10-20mm (3.4x3.5in) and 520g (16.1 oz)

About 1/2 the size and 1/4th the weight despite having a longer zoom range and faster max aperture at the wide angle. How do you explain that?

By the fact that "rules" no longer apply at the extreme end of the scale. Sigma 10-20 is the widest you can go on DX, without resorting to a Fisheye. And such lenses, as we know, are larger than regular lenses. Compare the 6.7-13 with the 10-30. Going by pure calculation, the former should be much smaller than the letter, BUT, because the point was not to make a small UWA with crappy IQ, but rather good IQ, the 6.7-13 is actually not smaller. And it doesn't even offer the extreme FoV as the Sigma. So yeah, the point here is, that if you want good optical performance in UWA, you have to "over design" the lens. That is why such lenses are bigger than you would expect and that is why you can't compare them with the likes of 10-30mm. Could Sigma have made the 10-20mm as small as the 10-30? Probably, but the IQ would have been terrible.

Ah . . . I see it because the N1 actually has a pseudo-aperture because DOF is far more important than anything else, to include equivalent light exposure density.

It is not far more important, but you can't only compare FoV and call it a day. Obviously we can't make the kind of photos with our V1+18.5mm like D610 users can with their 50/1.8. Do you agree on this?

Today's sensors regardless of size, CX, DX, FX, whatever use basically the same semiconductor technology. To borrow the phrase, there is no "Magic" that makes FX photo sites behave any differently when struck by Photons than those on CX or DX sensors.

The "magic" is the much larger size of DX and FX photo sites.

Larger Photo sites are better, in that all else being equal, they have inherently better signal to noise ratios. But, when photo site density is equal, baseline signal to noise ratio is also going to be equal, and thus usable sensor sensitivity is also equal.

That is correct, but there are no DX/FX sensors with photo sites as small as on CX sensors.

CX and DX (and M4/3rd for that matter) sensors typically have smaller photo sites, resulting in lower usable Maximum ISOs (before noise eats the image). So, the point is the TRUE f number equivalence is that which forms a part of the computation of ISO and Shutter Speed to generate a proper exposure. This is essentially equal for all sensors, regardless of size, assuming equivalent photo sites (and thus equivalent signal to noise).

Yes, but as I've said, there are no DX/FX lenses with such small photo sites, which makes it a moot point.

So, yes, I know your FF sensor is bigger than a CX or DX sensor. We agree, but that doesn't mean every other sensor out there really has a pseudo aperture . . . if so, then we should really be judging of of MF sensors, after all they're bigger yet.

Or large format.

But in all seriousness, the reason we don't use MF or LF in such discussions is that FF or 135 format was the most used for the longest time, making it the format most people are familiar with. Not for the "new kids on the block", who have began taking photos in the DX DSLR era, where there was no 135/FF, but for all the old-timers, who have made the jump from film to digital.

It's like horse power with car engines. It doesn't mean much from the scientific standpoint but it has established itself.

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