Diving into the past

In the past, PhaseOne has had a pretty strict policy for supporting third-party medium format cameras. However, this policy was watered down once PhaseOne made a deal with Fuji. As a result, the Fuji GFX series has been supported since version 11.3.
Until recently, with the update to Capture One 21 (14.4.0), the Pentax 645Z was officially unsupported.
I used my Pentax 645Z with Capture One since I own it. During this time I had to either patch the Capture One software with a tool made by Alex Munoz or tinkering the EXIF data.
Luckily, this has changed and I can just import the images into Capture One without any hassle.
But, let’s have a look back and talk about the previous options.

CaptureFix Pro and CaptureFix Fast

Alex Munoz created CaptureFix Pro and CaptureFix Fast as a solution to use Capture One for raw image processing of DNG files created by the Pentax 645Z.
CaptureFix Pro lets you choose input and output folders, with images arriving in the input folder remaining untouched while the images in the output folder are tweaked so that Capture One accepts them.
This has advantages and disadvantages. You will still have the untweaked images for backup or use in other raw converters. Clearly an advantage, however, you will use at least twice as much space on your disks. Despite using more disk space, you will have to make sure that both copies are available when working with different raw converters. However, I never used this tool as I preferred CaptureFix Fast.

CaptureFix Fast is using a different approach. You drag your Capture One application into CaptureFix Fast and it tinkers with the application. Afterwards, you can open Pentax 645Z files in Capture One and develop them. All files will get the generic DNG ICC profile assigned, the quality of this profile evolved over time but can still be a bit off.
However, this was a method I used for quite some time and in general, the results are okay unless you work with high ISO files and need to recover shadows. I encountered that the shadows tend to get a quite strong green cast, not corrected by an ICC profile I created for the camera. I always had to use a layer with a pinkish colour correction in the shadows to counterbalance the green tint and play around with the opacity. Furthermore, the high ISO images lack sharpness.

 

 

Faking the EXIF data

Another option was faking the EXIF data and pretending that the image is created by a PhaseOne IQ250, which uses the same sensor as the Pentax 645Z. All you need is “exiftools” and the shell to do it. However, as this is quite cumbersome, always remembering the correct parameters or creating an alias command for the shell.
A little search on forums helped me to find a script that can be added as a service to the Apple Finder. This made life a lot easier, as the script allows to convert lots of files in one go.
Nonetheless, the tinkering leads to the situation that you can no longer use the Pentax 645Z images in other raw converters like DxO Photolab.
Furthermore, the colours are a bit off mainly to the reds. But, the images are way sharper than before.

 

To deal with the colour shift, I created an ICC profile using the Lumariver Profile Designer. As you can see the result is really good.

   

Could I have lived with this solution? The answer is yes, Capture One is the raw converter I use for nearly all my images. Quite rarely do I use DxO Photolab, just when I need the “Deep Prime” noise reduction.

Native support in Capture One

Since the release of Capture One 21 (14.4.0) the Pentax 645Z is natively supported by Capture One. To be honest, it was quite a big surprise for me. However, this means no more patching or tinkering with the EXIF data. Just import the images into Capture One and they can be opened with DxO Photolab or Lightroom as well if you prefer a different raw converter for a specific image.
How is the colour rendering now? Have a look yourself.

 

Can it be further improved with a custom ICC profile? Maybe, slightly if you create a good profile. It also depends on your personal taste. These samples show the image with a custom ICC profile created with Lumariver Profile Designer.

 

If you look closely, you will notice that the images faking a PhaseOne IQ250 are slightly sharper. This is mainly because default sharpening for the IQ250 is a bit more aggressive than for the Pentax 645Z.

IQ250 fake  Native

An in-depth comparison of the colour renderings

Let’s have a closer look into how the colours are rendered using the different methods.
Capture One provides an excellent tool to do it, the “Color Readout”.

Using a patched Capture One version would give you these readouts.
On the left, you can see the image with the default white balance. On the right, the white balance has been adjusted and some of the green tints has vanished. Unfortunately, the shadows are still quite greenish.

Even with the adjusted white balance, the colour rendering for high iso files is mediocre.

So, let’s move on and compare the colour rendering for the IQ250 EXIF fake with the new native support. I created two variants for both scenarios, one with a built-in ICC profile and the other one with a custom ICC profile. The IQ250 fake uses the Portrait ICC profile, while the native 645Z uses the Generic ICC profile. Both custom ICC profiles are created from the same shot of an x-rite ColorChecker Passport using the Lumariver Profile Designer.
In the following images, you can see the colour readouts in the following order:
1st row: 645Z native with generic profile – 645Z native with a custom profile
2nd row: 645Z as IQ250 with Portrait profile – 645Z as IQ250 with a custom profile

As you can see, there is barely a difference between the custom profiles.

Finally, a quick comparison between all three ways to handle the Pentax 645Z files.
1st row: 645Z native with generic profile – 645Z native with a custom profile
2nd row: 645Z patched – 645Z as IQ250 with a custom profile

You will notice the difference between the variant using patched software and the others. Besides the colour cast, the image lacks sharpness.