Alpa 6x9 film focal length questions

[Mike M]

Hi, I'm thinking about switching to an Alpa 6x9 film setup but am having troubles making out exactly what the 35mm focal length equivalents are of many of the large format analog lenses.

These are the analog lenses that I've been researching on the Alpa website:
Schneider super angulon 38mm 5.6
Schneider super angulon 47mm 5.6
Schneider super angulon 58mm 5.6
Schneider super symmar 80mm 4.5
Schneider apo symmar 120mm5.6


Some places say that the 120mm is the standard lens for 6x9. Other places say the 80mm is the standard. I've also read that 100-105 is a standard lens. None of it makes any sense to me.

Are there any people around here that can tell me their experience of how the lenses in the list would relate to 35mm focal lengths if used to shoot 6x9 on Alpa? Thanks for any info

 

[VICTOR BT]

mike... it is always confusing... there are different ways to calculate, mainly because of the aspect ratio.
a basic calculation is one proposed by Linhof.
diagonal of the format = normal lens.
short side of it = wide lens.
2x the long side of the format = long lens

so in the case of the 6x9 on alpa (56x84), it is about 55/100/180
u want two lenses, both around normal - 80 and 120, those are equivalent to 35 and 50 if used on small camera.

now, to convert the format factor is also easy in this case, because both the 35mm camera and the 6x9 have the same aspect ratio - 2/3 (x1.5). there is no need for complex calculations. in other words, 6x9 of alpa/linhof is basicaly the exact same as leica only x 2.3 bigger in size
so, 100 (diagonal of 6x9 format) : 43mm (the diagonal of small format 24x36) = 2.3
from here, u can calculate anything...
for example, 58 schneider is equivalent to 25mm lens on leica. (58 : 2.3 = 25.2)

 

[Mike M]

Victor....Thank you! You just cleared up all of my confusion with that wonderful post

This is OT, but maybe some Alpa people will be surfing this thread and so it might be worth asking. Alpa's website cautions against using any lenses longer than 135mm for 6x9 because of the possibility of body vignetting. Does this mean that telephoto photography is basically not going to happen with Alpa 6x9?

 

[VICTOR BT]

dont know about telephoto vignetting of the body, but there is another issue that makes using telephoto lenses difficult on alpa. there is no correct focus indication (unless u use ground glass accessory in a very similar way to 4x5 camera). mount the GG for composition and focus, then remove it, mount the back+film... so actually, it is even more combersome than using 4x5 film holder, or the special sliding 6x7 holders (like linhof).
actually, alpa is primerally good for wide angle lenses, up to normals. for objects and scenes at long and down to medium distances. u simply guess what is the distance and set it on the lens focusing mount. it is easy with wide lens and up to moderate distance especially if u close the aperture to optimum.
otherwise, the longer the lens, the less Depth of Focus it has and it makes it more difficult to guess the distance correctly. the closer the object u photograph the more difficult it is to guess the correct distance, simply because there is no room for error since the Depth of Focus gets smaller and smaller at close distances.
guessing focus with telephoto should be ok for about the infinity setting and closed aperture to optimum.

 

[PeterL]

This spreadsheet may come in handy. Check out: ALPA_CFL_Calc_V217B.xls

http://www.alpa.ch/en/press/downloads.html

Cheers, -Peter

 

[Mike M]

^thanks for the link Peter

dont know about telephoto vignetting of the body, but there is another issue that makes using telephoto lenses difficult on alpa. there is no correct focus indication (unless u use ground glass accessory in a very similar way to 4x5 camera). mount the GG for composition and focus, then remove it, mount the back+film... so actually, it is even more combersome than using 4x5 film holder, or the special sliding 6x7 holders (like linhof).
actually, alpa is primerally good for wide angle lenses, up to normals. for objects and scenes at long and down to medium distances. u simply guess what is the distance and set it on the lens focusing mount. it is easy with wide lens and up to moderate distance especially if u close the aperture to optimum.
otherwise, the longer the lens, the less Depth of Focus it has and it makes it more difficult to guess the distance correctly. the closer the object u photograph the more difficult it is to guess the correct distance, simply because there is no room for error since the Depth of Focus gets smaller and smaller at close distances.
guessing focus with telephoto should be ok for about the infinity setting and closed aperture to optimum.

That pretty much confirms my thoughts too. Alpa really is made for normal to wide angle photography. Focusing is definitely going to take more care but I'm cool with all of the quirks. Actually, I'm starting to get kind of spiritual about photography and want the whole pace of the process to just sloooooow doooown ...if ya know what I mean

 

[Mike M]

This is an old thread, but I wanted to add a link for any surfers that might be stumbling upon it in a search.

Optechs Digital added an Alpa Lens Focal Length Comparison Chart to their site here: http://www.optechsdigital.com/Alpa_Focal_Equivalents.html