[swiz]

Can anyone who has owned the Pentax 67 300mm f4 EDIF and the 400mm F4 EDIF compare the two for me in terms of IQ and vignetting? Is one noticeably better than the other? I can live with either focal length for astrophotography but they must perfrom optically perfect for me to make the purchase. I am already sold on the 300mm after seeing several images and inspecting it under strict scrutiny, but the 400mm not so much. I see on hear in the reviews that the 400mm version of this lens exhibits some green chromatic aberration which I find questionable. Are the element configurations between these two lenses that different? I figured that a discussion on here with some experienced users would help me make up my mind. I need to mention that I plan to use either of these lenses with a canon aps-c sized sensor. thanks.

[gofour3]

Can anyone who has owned the Pentax 67 300mm f4 EDIF and the 400mm F4 EDIF compare the two for me in terms of IQ and vignetting? Is one noticeably better than the other? I can live with either focal length for astrophotography but they must perfrom optically perfect for me to make the purchase. I am already sold on the 300mm after seeing several images and inspecting it under strict scrutiny, but the 400mm not so much. I see on hear in the reviews that the 400mm version of this lens exhibits some green chromatic aberration which I find questionable. Are the element configurations between these two lenses that different? I figured that a discussion on here with some experienced users would help me make up my mind. I need to mention that I plan to use either of these lenses with a canon aps-c sized sensor. thanks.

You might get more of a response if you posted this question in the Medium Format section.

Pentax Medium Format - PentaxForums.com

Check out the lens reviews here:

Pentax 67 Telephoto Primes - Lens Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database

Phil.