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I found an illustration, which I modified a little bit in order to show the significance of when you use a Fujifilm GFX 50 camera, together with the Vertex Rotating adapter, and Pentax 6x7 lenses. How it corresponds in comparison to the classic film 6x7 negative, the native Fuji sensor 44x33mm and the normal fullframe sensor (24x36) and classic 35mm negatives.
You could say, the surface area - is even larger than the traditional Hasselblad 6x6 format (whose area measures around 56x56 mm).
That is why I feel this is so stunning
that with the Vertex adapter - you literally cover the Pentax 6x7 lenses entirely, like they were originally designed to do on film. As if there was no crop factor, as the method utilizes the entire image circle of 6x7 lenses !
Also: Without that the perspective gets distorted (which happens when you just stitch together a bunch of images. Instead: the 6x7 lens on the Vertex adapter never changes position. It is the camera which rotates around the optical axis of the Pentax 6x7 lens.
Full vs "cropped" Medium format
So, if we wish to emulate the real view from Pentax 6x7 lenses - the Vertex adapter allows this, when you use a digital medium format camera, such as Fuji GFX 50 or 100, and the Hasselblad X1D and X2D. And no, it does not work with the Pentax 645z, because of its mirror (distance between camera mount and lens does not allow any adapters, other than for 6x7 lenses - but not a Vertex stitching adapter or other kinds). This was only possible since the digital cameras became mirrorless cameras - allowing a lot more room for all kinds adapters, and special adapters like the Vertex.
Vertex + fullframe (24x36 mm sensor) cameras
When you use a full frame camera, like I do now, the total surface area results into "only" equivalent like using a 46x46 mm digital sensor. That is already a lot, and larger than a native Fujifilm GFX sensor. Also, you only use the optically better inner part of a Pentax 6x7 lenses - not the borders.
Kind of like when you use fullframe lenses on a crop APS-C or APS-H factor camera - with similar results. But to me, i find it super interesting, to use the Pentax 6x7 lenses, and get the "optical rendering", of the original lens all the way to the borders - like when you use film for 6x6 or 6x7.
Night Photography with a "7x7" Medium format camera
Now today's film emulsions are tricky when it comes to longtime exposures - because of the "Schwarzschild effect" - which is an effect, that in low light, films loose sensitivity. Some emulsions do it rapidly, such as Hungarian FOMA films. But also Ilford films loose a lot once you go down below 1s second, 10 seconds or even 100 seconds exposure times.
For a 2 minute exposure according to your light meter - you may end up having to expose a whole HOUR in order to get the shot correctly exposed (I believe that is the case with FOMA and ROLLEI films). I once did that with a 4x5" large format camera, for 1.5 hours. And the shadows were still vastly underexposed (at night). On top - the contrast in the film increases, due to this Reciprocity failure, as the shadows where least photons arrive, loose even more speed along time.
Digital sensor don't have Reciprocity failure
So, you can utilize your "Digital Pentax 7x7 camera", go and make pleasantly night exposures, without that the exposure drifts out of proportions with 1 hours exposure times. Because it isn't necessary to compensate with digital sensors.
Fuji Acros 100 film - least reciprocity failure of all
The best film who exhibits least amount of "Schwarzschild effect" (also known as Reciprocity Failure / Effect), is the Fuji Neopan ACROS 100 II film. It really strand out to be the very best of all film emulsions that exist today.
All other films have more or less that Reciprocity Failure, with vastly reduced sensitivity in low light. For example, the Kodak T-MAX 100 becomes more sensitive than the T-MAX 400, when your light meter shows let's say 1 minute exposure time. Then the T-AMX 100 needs a relatively shorter compensation, than the T-MAX 400. Tri-X 400 is even worse...
The world at night is different
(film reciprocity failure examples)
Let's have a look in the table. You can see, that if you light meter says 10 minutes exposure time is needed - then together with the Reciprocity failure, you need 27 minutes exposure time when using Kodak TMAX 100 film - but a whopping 46 minutes with the T-MAX 400 !!
The sensitivity of the normally 2 stop more sensitive T-MAX 400 film, is suddenly less sensitive than the T-MAX 100 film.
The world at night is different...
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