Hello everyone,
I did two aerial photography sorties on an Asian city last year using the Pentax K1 with 77mm f1.8 Limited and Pentax 645Z with 55mm f2.8 and 90mm f2.8 SR lens. The Asian city is, unfortunately, not as awash with light as most big European or American cities are in the night.
The Pentax K1 with the 77mm Limited f/1.8 gave me decent images at 6400 ISO at about 1/45 sec with K1 IBIS on, but only in situations where the experienced pilot managed to inch forward slowly while keeping the helicopter vibrations low to the extent he could. These images are sharp enough, so the IBIS of K1 seems to work. The Pentax 645Z images, shot at ISO 12800 were pretty dark as they were all shot at 1/250 to 1/500 due to the lack of IBIS in the Pentax 645Z.
I got a few images from the K1 printed recently. The PP was done by someone good at it. Some images are reasonably good upto 8x10 size. I can't share the images as yet due to the confidentiality clause.
I believe the Fujifilm GFX 100 or the new 100S with IBIS upto 5.5 stops and coupled to Pentax 645 55mm f/2.8 or 90mm f/2.8 might produce better images than the K1 with IBIS or the 645Z without IBIS. However, will the Pentax 645 55mm f2.8 or 90mm f/2.8 resolve adequately on the 100MP sensor of the Fujifilm GFX 100S?
How would be the high ISO performance of the Fujifilm GFX say at ISO 6400? If I can shoot at that ISO with shutter speed upto 1/100 with IBIS on and lens wide open, I think I can get pretty decent images even in the low light levels of the city in the night, going by my experience with the K1, which isn't really meant to be a high ISO performer.
The thought of using the new Fujifilm GF 80mm f1.7 on GFX 100S for night-time aerial photography (because of the 1.5 stop advantage compared to the Fastest Pentax 645 lenses) is very tempting, but for the cost. To reduce the cost, but to get another extra stop of light, the Mamiya 80mm f1.9 seems another choice, but again will it stand up to the 100MP sensor of the Fujifilm GFX 100s? And is the f1.9 of the Mamiya more like f2 or like f1.8? I would like to know how many additional stops of light I will get compared to the fsstest Pentax lenses at f2.8.
Finally, what about the Sony A7S iii? Meant to be an excellent performer for low light photography, would it be better than the Fujifilm GFX 100S at ISO 6400? What about its only 12MP resolution? Ideally, I would like to print the images to 20x30 size; in the worst case, at least 16x20 size.
Also, Just to add, I managed to get a good copy of the Pentax 50mm f1.2 on ebay. It is reaching me in end of March. So I will get an additional stop of light compared to the 77mm Limited f1.8. Every bit of extra light gathering capacity of the lens would help to bring down the ISO or increase the shutter speed. I hope that the Pentax 50mm is as good as the Pentax 77mm wide open.
I would be thankful for the kind advice of the forum members.