A Viewfinder Darkly

Photography tips and tutorials

Pentax K1 exposure metering

January 13 2017

by Philip Northeast

The Pentax K1 offers a choice of three standard exposure modes for measuring the light coming through the lens for determining the exposure settings.  Also, there is some internal processing that influences the exposure independently of the normal camera exposure controls.

The Pentax K1 is a high-resolution full-frame DSLR  for advanced photographers, this gives the point of view for this evaluation.

Shady rivulet

Hobart Rivulet: bright sun means dark shadows providing a challenge for metering systems

The metering system uses an 86K pixel RGB sensor with the metering modes using all or some of these pixels.

Multi-segment

This metering mode analyses a number of segments in the view to get an exposure that is a suitable compromise for all the elements in the photograph.  Pentax say in this mode there is exposure compensation  for backlight conditions

Centre weighted

This mode gives more importance to the exposure for the centre of the image and less to the off centre elements.  This may be more suitable for difficult exposure situations or portraits.

Spot metering

This mode even more restrictive in the area evaluated, and measures the light only in the centre of the image, ignoring the remainder of the view.   Spot metering is intended for precise metering in difficult lighting situations.

To enable metering for older Pentax manual lenses photographers need to go to the CustomMenu, screen 4 and right at the bottom item 26 in the custom menu and select enable aperture ring.

The exposure information from the metering system determines the settings of Aperture, Shutter Speed, and ISO. However, that is not the end of the story in modern digital cameras. There are a number of systems that influence the exposure of the photograph.

D-Range Settings

The D-Range settings are supposed to expand the dynamic range of K1 in difficult lighting conditions. Such as where there is a large difference between the darkest and brightest elements in the scene.

Normally I never use these features, but for this test, I took some shots with them turned on. A dimly lit room with a bright television in the shot provided a tough test for the Pentax K1. The only difference between the two shots was turning the D-Range processing on and off. The D-Range processing did reduce the amount of clipping in the highlights on the television screen. There is still some highlight clipping. The wall in the darker area looked brighter in the D-Range version.

compare D-range

Left: no D-Range Middle: D-Range Right: left pic edited in Lightroom

To make it work properly the ISO setting has to be a minimum of 200.  This is where I have my doubts about these systems. The intention is to improve the dynamic range of the system, but raising the ISO to 200 reduces the dynamic range of the K1, according to the tests by DxOMark. I always use ISO 100, the lowest setting because it gives the K1  a distinct Dynamic Range advantage.  I always save the raw image data and process later in Adobe Lightroom. The complete information in a raw image gives plenty of scope to compensate for many extreme light ranges in post processing.

Processing the normal image in Lightroom made more difference in bringing out shadow colour and removing

Image finishing Tone 

The Pentax K1 applies a number of tone settings to the image in the capture process. These are applied to any jpeg files produced in the camera and are the default view for raw data images. The advantage of raw files is that in post-processing users can apply their own tone settings without losing detail as is the case for jpeg processing

Photographers can adjust these default tone settings. On the 4 way controller select the right side control. This brings up a menu to specify the finishing tone (Page 66 in the manual).

menu display

The finishing tone menu on the Pentax K1

These adjustments are stored in the raw file for each image and used when displaying the initial raw file in post processing.

The problem I have with using these settings is that they applied equally to every photograph without regard to the characteristics of the scene. I  set them to the neutral position and make any adjustments in later to suit the individual photograph.

The default setting is the bright option that has the contrast and brightness at the +1 setting. This explains my initial feeling that all my photographs with the K1 were too bright and needed correction in post processing.

Summary

Even with all the technology my personal view is that the photographs I take on bright summer days are still slightly overexposed. The most important thing is that the metering seems consistent, so it is easy to correct any slight overexposure. The key point is that I would expect photographers using this class of camera to use the raw image data. They should carefully make their own final adjustments in post processing for each scene rather than settle for a one size fits all exposure setting.

 

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