A deep dive into the Sigma FP2’s image quality finds a camera that’s unconventional to its core

Sigma states that the base ISO of the FP2 is 320, rather than the ISO 100 that Nikon and Panasonic use for the same sensor. And in that one decision is a key clue about what’s going on.

The ISO settings on cameras refers to a JPEG-based standard; one that gives camera makers a lot of leeway in terms of how they choose to use their sensors, at the Raw level. For instance, the standard allows manufacturers to decide to give their sensors less exposure, by default, in order to capture more highlight information. When the ISO standard was changed in 2009, we saw many manufacturers make small adjustments to capture a little more highlight information, so that their JPEGs could give a more progressive highlight rolloff, in exchange for a slight noise cost that comes from using less exposure.

Sigma is going much further than this. Rather than adjusting exposure by a one- or two-thirds of a stop, it’s rating its base ISO one and two thirds lower than Nikon or Panasonic are choosing to. And, as with the Sigma BF, the reason is much more than just giving a more progressive JPEG highlight rolloff: it’s making sure the camera captures enough highlight information to let it deliver true HDR images, with more lifelike representation of bright highlights (when viewed on a device with a high-brightness screen).

Studio scene

In terms of detail, the Sigma FP2 is a close match for both the Panasonic S9 and the Nikon Z6III. The Nikon appears a little more detailed, but that may be more down to fractionally different focus or the different lenses we have to use. Though, because it has no anti-aliasing filter, the Sigma exhibits a little more moiré in the smallest detail it can capture.

Both the Nikon and Panasonic are more successful at presenting fine detail in their JPEGs, with the Panasonic doing a better job of doing so without tipping into looking over-sharpened. This 1:1 view isn’t necessarily how many people will view 24MP images, though.

In terms of noise, the Sigma appears to be a close match for the Nikon, despite their differences in terms of exposure strategy (the Sigma is applying less gain at each ISO setting, but this is a dual conversion gain sensor that’s essentially ISO invariant in its higher conversion gain mode, so this approach makes no meaningful difference). Where there is a difference is at base ISO: because the FP2 has a base ISO of 320 and an Auto ISO system that defaults to ISO 400, it means the camera will try to use two stops less exposure than the Nikon when shooting in bright light. That’s a decision that will limit peak image quality. Unless you choose to work around it.

HDR images

The FP2’s images look pleasant enough when viewed as SDR but can be really impressive when viewed on an HDR-capable device. We found images with bright features such as neon lights, reflections in chrome and light glowing through petals or leaves are where its HDR output really shines. However, we also found that some subjects, such as light-skinned portraits, really didn’t work well. It’s one thing to describe someone as looking ‘radiant’ or ‘luminous’, but the reality of photos in which the skintones glow, but freckles and other facial features don’t, can be deeply unflattering.

Richard Butler

There’s no way to disengage the camera’s HDR function, so you may find yourself choosing to flatten the images down to SDR on a case-by-case basis.

Exposure strategy

Looking at the Raw levels (and the 1.67EV higher-than-usual base ISO rating), we see that, from ISO 320 upwards, the Sigma’s exposure/gain configuration is set to capture around five stops of highlight information above middle grey, rather than the 3.3EV that Nikon has opted for, in the Z6III. This is entirely consistent with a camera whose images are trying to show up to 1.67EV of additional highlights beyond what a conventional SDR JPEG would include. As with the extended ISO settings on any camera, drop below base ISO and you clip highlights increasingly early. In this instance, ultimately dropping you back to the same 3.3EV of highlights as its peers, by the time you reach ISO 100.

There is, inevitably, a noise cost to be paid for these lower exposures, so if you aren’t after HDR output, it’s worth considering manually adopting ISO 100 in bright conditions.

Ultimately, the FP2’s full-time HDR approach is why the camera’s Auto ISO system always chooses a higher ISO. The only remaining puzzle is: if base ISO is 320, which does Auto ISO favor ISO 400, instead?

Follow DPReview to ensure our independent journalism reaches your feeds.