A reader recently commented:
“Fujifilm is developing lenses like 23mm f/1.4 and 56mm f/1.2 for the Fuji X cameras. That’s pretty close to f/2 on Full frame cameras. It makes me wonder about the logic of Sony coming out with compact f/2.8 lenses for full frame cameras. Seems like compact lenses f/2 or under would be what makes it special. Why else would you buy the FF over APS-C if you can’t get better shallow depth of field for a camera of similar form factor.”
I wanted to add my thoughts here to a wider audience since some may not be following the comment thread on that particular post. Now before this is taken as Fuji-bashing and Sony fanboy-ism let me say that Fuji was my first love. Had the X-Pro1 been first on the market I probably would have gone Fuji and never looked back. Ten years ago I shot with a Fuji S600Z (I believe it was called) and had many of my event and publicity pictures published. It seems crazy now to think that a three megapixel bridge camera was good enough but some of those images are still some of my best.
It is true that these fast lenses are going to be very close in depth of field to a f2.8 lens on a full-frame camera. However, I don’t think depth-of-field is the most compelling reason to go full-frame. Let’s look at a few:
1. Dynamic Range: let’s look at the Nikon D7000 vs. the D800. Much has been made about the fact that the D800 has essentially the same sized photo sites so on a per-pixel level the dynamic range should be the same:
Dynamic range of the D7000 vs. D800 compared on DxO Mark
What we find is that on a total sensor evaluation the greater number of pixels and imaging area–for the same field of view–yields better dynamic range. The same is largely true for noise at high ISO as well.
2. Sharpness: a sensor itself is not “sharp”. Sharpness is always a function of the sensor and lens combined. For example, the Sony RX1R trades flexibility for absolute sharpness by perfecting mating a single lens to a specific sensor. The Zeiss 35mm f/2.8 is likely to be much sharper across the frame wide open than the Fuji 23mm f/1.4–even if the depth of field is the same. The faster the lens the harder it is to correct for contrast & sharpness robbing aberrations also …
3. Wider Field of View at the Same Focal Length: this matters because wider angles are more difficult to make faster AND sharper (while this is off set somewhat by the smaller format size check out these comparisons). Also, a 23mm lens is going to reach a hyperfocal distance (where everything or nearly everything is in focus) much sooner than the full-frame “equivalent” 35mm lens.
4. FLEXIBILITY: Personally this is the most compelling reason for the full-frame NEX and what the camera could, or should, hold over its rivals. A high megapixel mirrorless full-frame camera will the compatible with the widest array of lenses and accessories. This can lead to terminal LBA but also more creative opportunities as you can mount virtually any lens. A mirrorless medium format digital camera would of course be MORE flexible by the same logic but to me that would past he point of diminishing returns (too big, expensive, etc.).
For someone who already has a good collection of high-quality lenses the full-frame NEX could actually be cost saving (at least initially):
Flagship NEX APS-C camera: $1200-1500
Zeiss 24mm f/1.8: $1100
Touit 32mm f/1.8: $900
Sony 50mm f/1.8: $300
Full-frame NEX camera: $3000 (rumored)
Contax G Zeiss 28mm f/2.8, 45mm f/2.0, 90mm f/2.8: $0–I already own them*
I also own a set of Nikon non-Ai primes and some M-mount lenses (50mm & 15mm) that probably won’t have the same corner sharpness wide-open on a full-frame NEX but would now work at their “native” field-of-view. So I’d have all those options as well plus the ability to crop into APS-C size if/when I want it!
*full disclosure: I payed around $600 for the set, so if I were to buy them now it would cost about the same but for better image quality and a focal length I prefer at the long end.