Comparing systems vs. comparing sensors.

Started Dec 25, 2013 | Discussions thread
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57even
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Comparing systems vs. comparing sensors.
Dec 25, 2013

Firstly HAPPY CHRISTMAS ONE AND ALL.

Now, back to photography.

A system is what takes pictures (camera plus lenses) hence systems are what one should compare. Not theoretical advantages of one sensor or another used in ideal conditions.

My two "systems" are based around a D800 and a Fuji Xpro1, I think that is a good and tough basis for a comparison. The Xpro1 vs. Dx0's best DSLR camera ever for DR and resolution. Prior to the A7r anyway.

Surely the Xpro1 can't compete for IQ? Well, in the real world it's not so simple. Sometimes it really does. And it's down to lenses.

The 23mm F1.4 for instance is entirely usable at max aperture. This means I am normally comparing with FF lenses (28 F1.8 or 35 F1.4) stopped down to F2 or 2.8 to overcome one or more issues, such as longitudinal CA, poor contrast and purple fringing, not to mention focus shifting and field curvature. Many of these issues also apply to the faster telephoto lenses too. Moreover, there is such a thing as too little DOF.

So in practice, at least at wider to short telephoto focal lengths, I don't see any real advantage to the Nikon in terms of DOF control, or low light noise. Nor do I see any DR improvement in lower light because I am using higher ISO as a result of stopping down. Furthermore CDAF off the sensor is notably more accurate. No focus shifting or constant chimping to see if I have the object in focus. I can only replicate that with the Nikon in live-view mode, which requires a tripod. Thin DOF work is hard work. Easier with Fuji, on the whole.

So for hand-held photography in variable light, the Fuji actually wins most of the time simply because I can open the lenses right up and nail the focus. This evens out the amount of light hitting the sensor and overcomes any advantage from a larger sensor. As a street camera, I get better results (in terms of overall IQ) for a larger percentage of the time with the Fuji, even if you ignore the size and weight advantage.

Of course, the Nikon wins for landscapes in good light and for long exposures on a tripod. Lenses are stopped down, I have 36MP not 16MP, and the shadow DR at ISO 100 is amazing. But I don't get the full theoretical advantage. Even stopped down many wide angle FF lenses show a visible variation in sharpness across the frame, especially in the corners. By contrast, the Fujis show very little. Moreover, to achieve the required DOF for landscapes, one is already starting to see diffraction take the edge off resolution.

Sure I can still see the advantage of 36 vs 16MP in the fine detail, at least in the centre frame, but only in prints of 24" or larger, and even then only if I am looking for it. Many people don't immediately see that and many subjects don't really require it.

DR aside, the much anticipated 24MP Xpro2 should not have much if any resolution penalty over the Nikon, thanks to the exceptionally sharp optics optimised for the APSC image circle. I reckon it will be even harder to tell them apart, even under ideal controlled conditions.

Of course, once we come to sports and events, any top end Canon or Nikon SLR will beat any CSC camera because of tracking AF, exotic long lenses, and PTTL/iTTL flash. No competition there, which is why I hold on to the Nikon.

So if the lenses keep the Fuji's head above water compared to the Nikon, why not a FF Fuji with equally excellent lenses?

Firstly, it wont be an SLR, so it will have none of the main advantages of the Nikon in terms of sports and events. But surely it will have the other benefits (resolution, DR)?

Not necessarily. Look at the Sony A7. The entire lens roadmap consists of relatively slow lenses. Even by 2015 the only fast prime is a 55 F1.8. Why? Simply because a smaller form factor makes large, heavy, fast lenses eliminates much of the size advantage. Also, with such a close registration distance, I suspect fast lenses are much harder to make if you want to control edge effects (look at the Leica performance on the A7).

I have no doubt Fuji would face similar challenges. For fast lenses it would need a larger lens mount and probably slightly larger registration distance (would make adapters harder to design). It could well end up being closer in size, and weight, to a Canon 6D/Nikon D610.

Otherwise, you're back to slower lenses again, in which case, compared to a probable 24MP Xpro2 with the existing (announced) lenses, the resolution would be comparable and the only advantage would be DR in daylight conditions and long exposure shooting. Nice, but not worth the likely doubling in price, IMO.

 57even's gear list:57even's gear list
Fujifilm X-Pro1 Nikon D800 Fujifilm X-E1 Sigma 20mm F1.8 EX DG Aspherical RF
Canon EOS 6D Fujifilm X-Pro1 Nikon D610 Nikon D800 Sony Alpha 7 Sony Alpha 7R
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