Fuji X-T2 announced

[Akira]

The on-site PDAF sensor will be defunct before the light drops to the EV rated in the catalog.  Panasonic's AF system independent of PDAF is more consistent and successful.  The AF performance should also be highly dependent on the algorithm beside the chip technology.  So long as The Camera Store TV reviews are concerned, the video AF performance of Sony is not as reliable as that of Canon.

[Akira]

Of course, the AF is more challenging on the larger format, which should be counted in when comparing the technology and the performance of AF.

[bjornthun]

Fuji specifies that contrast AF in the new Fuji X-T2 goes down to -3 EV and says that contrast AF excels in low light, see here http://www.fujifilm.com/products/digital_cameras/x/fujifilm_x_t2/features/page_02.html

This means that the new copper wired Sony APS-C sensor is capable of -3 EV sensitivity when using contrast detection.

What we don't know in some of the Sony specs is, if PDAF or contrast AF is listed. In case a sensor offers both, both should be listed. Here is a list of Sony A7x specs from wikipedia: https://en.m.wikipedia.org/wiki/Sony_A7
It appears that we go from 0 EV to -4 EV depending on the camera body. The A7s models use contrast AF and both go to -4 EV. The A7R2 goes to -2 EV, and has the newest sensor of the A7x models.

This is pretty much a moving target.

[Ilkka Nissilä]

Also the specification should be for a) static subject, b) an approaching target using a standardized test protocol. It could be e.g. equivalent to a bride approaching the altar in a dimly lit chuch, which is a commonly encountered and often challenging AF problem.

Smaller sensors lead to a more challenging AF problem since the smaller scale of image means the focus must be achieved correspondingly more precisely than with a larger sensor system to reach a given final sharpness in the image. However, it seems typical that larger sensors take more time to read the data for reasons I'm unfamiliar with.

[simato73]

As mentioned, the low-light performance of AF of APS-C Alpha can be a bit outdated.  Panasonic cameras can focus in the darkness of as low as -4EV (even the entry model GF7).  Olympus doesn't publish the low-light limit of their AF sensitivity, but, based on my experience with E-M5 MkII, its AF performance is practically on par with that of GX8 that I also owned briefly.

The data read-out of the full-frame sensor is inevitably slower than that of the smaller APS-C or m4/3 sensors, which lead to the longer lag in the display of the viewfinder images.

So, neither full-frame or APS-C Sony cameras are as "well-rounded" as those of Fuji or Olympus or Panasonic, even if the image quality offered by the current full-frame and 24MP APS-C sensors can be fantastic.

Thank you for explaining.
If you happen to have the opportunity to handle a new X-T2 I'd be interested in your opinion.

[Frank Fremerey]

I love the X. My X100T is a hell of a camera for her price and size. Yet I have so many Nikon options right next to me on my table that I only think of lenses I do not get for Nikon.

Guess what the first lens is that comes to my mind?  ... 1.8/75mm Zuiko ... and 4/300 Zuiko ...  gosh, I am lusting for these, although I generally do not like the OM-D user interface, but there are still some PENs.

The 1.2/56 Fuji Lens is very very good (and the XPro2 feeld perfect in my hand), but I already have an 85mm Nikkor with very decent bodies to use it on, so what?

In the end I come back to Nikon and hope for the 850 or 900 and more of this wonderful Nikon glass.

[Akira]

Fuji specifies that contrast AF in the new Fuji X-T2 goes down to -3 EV and says that contrast AF excels in low light, see here http://www.fujifilm.com/products/digital_cameras/x/fujifilm_x_t2/features/page_02.html

This means that the new copper wired Sony APS-C sensor is capable of -3 EV sensitivity when using contrast detection.

What we don't know in some of the Sony specs is, if PDAF or contrast AF is listed. In case a sensor offers both, both should be listed. Here is a list of Sony A7x specs from wikipedia: https://en.m.wikipedia.org/wiki/Sony_A7
It appears that we go from 0 EV to -4 EV depending on the camera body. The A7s models use contrast AF and both go to -4 EV. The A7R2 goes to -2 EV, and has the newest sensor of the A7x models.

This is pretty much a moving target.

According to the catalog, the lowest limit of AF sensitivity of the newest A6300 is -1EV, which is not impressive.  Apparently the relative pixel size (A7S2>A7R2>A6300) is related to the lowest limit of the AF sensitivity (-4, -2 and -1EV respectively).

[Akira]

Also the specification should be for a) static subject, b) an approaching target using a standardized test protocol. It could be e.g. equivalent to a bride approaching the altar in a dimly lit chuch, which is a commonly encountered and often challenging AF problem.

Smaller sensors lead to a more challenging AF problem since the smaller scale of image means the focus must be achieved correspondingly more precisely than with a larger sensor system to reach a given final sharpness in the image. However, it seems typical that larger sensors take more time to read the data for reasons I'm unfamiliar with.

Ilkka, thanks for sharing your insight from the practical point of view.  Indeed the catalog data don't specify the character of the target, but, in general and according to my experiences, the catalog data coincide pretty well with the real-world performance.

[Akira]

Thank you for explaining.
If you happen to have the opportunity to handle a new X-T2 I'd be interested in your opinion.

I will post my impressions here.

That said, the biggest complaint personally would be their retro design craze.  The same goes for Olympus (and also Panasonic recently).

[bjornthun]

According to the catalog, the lowest limit of AF sensitivity of the newest A6300 is -1EV, which is not impressive.  Apparently the relative pixel size (A7S2>A7R2>A6300) is related to the lowest limit of the AF sensitivity (-4, -2 and -1EV respectively).

The A7S and A7S2 only feature CDAF, A7R2 and A6300 offer PDAF as well, so this is apples and oranges, if you go by pixel size only.

There are two figures to be quoted for mirrorless cameras that feature PDAF, the low light sensitivity for CDAF (contrast) and then the low light sensitivity for PDAF (phase). There is no reason to assume that these coincide a priori.

Both the Sony A6300 and the Fujifilm X-T2 use the new copper wired sensor from Sony. How do you reconcile Fuji stating -3 EV and Sony stating -1 EV? I reconcile those figures this way; Fujifilm states the CDAF figure and Sony the PDAF figure. Indeed Fuji says -3 EV for CDAF on their official web site, stating that CDAF "excels" in low light. Does Sony in their catalogue say if their figure for the A6300 is for CDAF or PDAF?

[Akira]

I didn't say that the low-light limit of PDAF and CDAF sensors coincide.  Rather contrary.  When Nikon released threir first Nikon 1 series, the designers said in one of the interviews that the PDAF will stop functioning earlier than CDAF when the lighting becomes dimmer (although the sensor was not made by Sony at that time).  The engineers refrained from mentioning at which EV the PDAF stop functioning.

Considering that the manufactures tend to impress better performances of their products, it should be safe to assume that the low-light limit of AF performance of mirrorless cameras published on the catalogs is based on the performance of CDAF.  Then the pixel sizes should matter.

[tommiejeep]

Guys , a very interesting discussion.   There are a few people that try and work out how different manufacturers "cheat" on their marketing.  Since I shoot with Sony, Olympus and Nikon I just work out what cameras work for different things as I shoot my normal images and not worry too much about the technical details.   I keep trying to find a good deal on a Fuji X-trans just to give one a try but little success so far. Fuji's seem to hold their value well.  I really wish Sony would simplify their UI (and drop the prices) .   Funny, but for what and how I shoot, the Sony a7II is not miles ahead of my D700 IQ-wise  .  I just could not justify the expense of a7RII or a7sII.   In hindsight, should have bought fewer Native lenses and gone for the better body 
The X-T2 looks a very nice upgrade.
Tom

[Frank Fremerey]

Funny, but for what and how I shoot, the Sony a7II is not miles ahead of my D700 IQ-wise  .  I just could not justify the expense of a7RII or a7sII.   In hindsight, should have bought fewer Native lenses and gone for the better body 

That is interesting. The D600/610/750-Chip inside the A72 is well above the D700 offering. It counts roughly three times the photons at the same ISO. Now that is should be somewhat degraded by Sony peripherels? Very interesting.

[Jan Anne]

I wish more cameras followed Fuji's classic button design with all the dedicated dials clearly marked on top.

One look is enough to see which lens is being used, at which aperture, shutter speed, ISO, etc.

Image hosted on DPR

I like the button programmability of my Sony's but basic functions should just have dedicated buttons or dials like on the Fuji or Df cameras IMHO.

[Bjørn Rørslett]

"... basic functions should just have dedicated buttons or dials like on the Fuji of or Df cameras IMHO"

Hear hear.

(a Df user since 2013)