Fuji XT-1 ISO Performance

I recently began using Fuji XT-1 cameras for most of my commercial projects. Especially weddings and events. One benefit is smaller size. Another is a nice collection of prime and zoom lenses. Since low light is a reality at wedding receptions and other indoor locations, one important consideration is ISO performance.

The X Trans sensor used in the Fuji XT-1 has a non-standard bayer array of green, red, and blue sensitive photo sites. The this pattern is used by the raw processing software to create a viewable file from the raw photo site data collected by the sensor when the shutter is tripped. Every sensor has a native ISO. That is the ISO that does not require any electrical or firmware manipulation when the sensor is exposed to light. Although the manufacturers tend not to make that information readily available, most web sites I’ve visited that focus on the Fuji X system state the native ISO for the X Trans sensor is 200.

The ISO dial on the camera has these setting options; L, 200, 400, 800, 1600, 3200, 6400, H1, H2. The numbered ISO settings correspond to firmware gain controlled sensor sensitivity to light. The L, H1 and H2 setting are essentially over and under exposures that are adjusted in the camera raw converter or assigned to the ISO block in the raw file for software processing on a computer.

I NEVER use the L and H ISO settings. Its easier to manipulate the exposure in post processing the raw file.

Here are a series of test shots to illustrate the image quality degradation that results from increased ISO settings when shutter speed is used to compensate for exposure. The ISO 200 exposure was F 1.4 at 1/15th second. The XT-1 was mounted on a tripod the shutter was released by pressing the shutter release. The lens used was a Funinon XF 56mm F1.2.

All the images were cropped to 1807 pixels square and then exported from Lightroom at 1804 pixels on a side. I used that cropping and export size to ensure that the images are 100% crops to make seeing the differences easier on the internet.

Here is the ISO 200 image:

ISO 200

ISO 200

Here is the ISO 800 image:

ISO 800

ISO 800

Here is the ISO 1600 image:

ISO 1600

ISO 1600

Here is the ISO 3200 image:

ISO 3200

ISO 3200

and here is the ISO 6400 image:

ISO-6400

ISO-6400

Its evident that noise becomes a factor as the ISO goes up. Fortunately the noise has a grainy appearance which one expects with higher ISO images.

Incidentally, all  these images are color, without B&W conversion. It just happens that the cropped area of the image includes only gray scales elements. The color square of the color checker have no noticeable color noise. Just the same grainy appearance as ISO increase.

The pixel size of the image also illustrates that quite a large print can be made from these files without objectionable noise. 1800 x 1800 prints as a 6×6 inch print on most light jet printers.

I trust this is useful for you, I know it was an interesting test to perform. Not difficult and confirms the ISO performance of the Fuji X Trans sensor.

One Man’s View,

David