Project:
Sigma APO 150 mm f/2.8
vs
Pentax SMC 67 165 mm f/2.8

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

Content:

1. Camera lens vignetting
2. Histogram and vignetting
3. Analyze of Sigma APO 150 mm f/2.8 vignetting
4. Analyze of Pentax SMC 67 165 mm f/2.8 vignetting
5. Analyze of Pentax 67 at f/2.8 and at f/4.0
6. Pentax 67 165 mm lens mounted on a Canon full frame camera
7. Pentax 67 and Sigma APO star test at center
8. Pentax 67 and Sigma APO star test at corner

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

1. Camera lens vignetting

Note:
I have updated the text and photos, several times.

I have used my Sigma APO 150 mm lens a while now and I'm very satisfied with it. Both when travel and when doing astrophotographing. It's just one detail, I feel it vignett a bit to much in the corner (full frame), in some corner almost 50% at aperture f/4. Before I bought this lens I used a medium format lens, the Pentax SMC 67 165 mm f/2.8.

I bought this Pentax 67 (6x7) medium format lens because of its long back focus and big image circle, it shouldn't vignett very much on a full frame sensor. It handle a sensor (film) up to 60 x 70 mm, very far bigger then todays tiny sensors. But it's an old construction and no APO. The lack of APO was the main reason that I later bought the Sigma APO, and then I also got auto focus. For astrophotographing I can do the focus manually. But I must admit since I started to use the remote control app it's very convenient to focus the lens without touching it, no vibration. These both lenses are aimed to my portable mount Star Adventurer.

The Pentax lens has collected a lot of dust since the last time I used it. I have old data from flat calibration that I can use to compare the vignetting of these two lenses. What I remember it wasn't very much vignetting at Pentax. But the resolution was maybe at least one class down compare to the Sigma APO.