Pentax 645Z Review
Dynamic Range
We are not in a position to measure the sensor's dynamic range, but we can illustrate the dynamic capabilities by recovering image detail from a series of under- and overexposed images. We shot the images in RAW+ and used Adobe Camera Raw to recover the detail from the (14-bit) DNG images. Below we compare these recovered images with out-of-camera JPGs.
The processed RAW images were sharpened with unsharp mask, 70%, radius 0.7. ISO was 100, the lens we used was the smc Pentax-DA 645 55mm F2.8m, and we shot at F5.6 in manual exposure mode.
Click any thumbnail to enlarge and browse.
| | Original JPG | Processed from RAW |
| -5 EV |  |  |
| -4 EV |  |  |
| -3 EV |  |  |
| -2 EV |  |  |
| -1 EV |  |  |
| 0 EV |  |  |
| +1 EV |  |  |
| +2 EV |  |  |
| +3 EV |  |  |
| +4 EV |  |  |
| +5 EV |  |  |
The amount of detail that can be recovered from the shadows even at a five stop underexposure is phenomenal and indicates a wide dynamic range similar to what was offered by the acclaimed 16-megapixel sensor in the Pentax K-5. At the other end of the scale we find what must be expected: when the highlights blow out, there often little to no data left to recover.
The 645Z has inherited the light meter from the K-3 and shows no tendency to overexpose on its own which is very good. The 645Z does underexpose at times (see the original JPEGs on our sample photos page), however.
Next up are 100% crops: The thumbnails below are 300 x 400 pixel crops from the processed RAW images, no scaling of resolution has been done.
Click any image to browse.
| | 100% crop from processed RAW |
| -5 EV |  |
| -4 EV |  |
| -3 EV |  |
| -2 EV |  |
| -1 EV |  |
| +/- 0 EV |  |
| +1 EV |  |
| +2 EV |  |
| +3 EV |  |
| +4 EV |  |
| +5 EV |  |
At ISO 100, images shot with 3 stops of underexposure can be recovered with no increased noise in the dark areas. Recovering from four or five stops underexposure does produce additional noise.
The sunlit highlights could not be fully recovered even with just one stop of overexposure, but the image as a whole was still usable at +1 and +2.
Verdict
The Pentax 645Z has a very wide dynamic range and recovery of shadow detail is possible with good results from severely-underexposed images. We have not attempted to quantify its dynamic range, however.
Regarding highlights, what we can say is when in doubt, it's generally safe to underexpose and simply recover shadows.
