View Full Version : 75mm Biogon Coverage
Jason Greenberg Motamedi
I am considering purchasing a 75mm Biogon: I need a fast wide angle lens which is sharp when used at its largest aperture. However coverage is a concern. I have seen an IC of 165mm, but was wondering if this improves at all when the lens is stopped down. Any help is appreciated.
Sorry, coverage doesn't change much with aperture. Per the Vade Mecum, coverage falls with stopping down "An 'AGI originated' lens when remounted, covered at f32 an image diameter of 84.7mm extremely well and evenly, and this is equivalent to 66x56mm on a '6x9' rollfilm holder, and this increased to 87mm dia at larger aperture, but the outer part was less evenly illuminated ... "
I have an ex-AGI F135 38/4.5 Biogon remounted in Copal 1. It covers about 87 mm, with 84 mm of good illumination, from f/4.5 through f/11. I've never shot it at a smaller aperture. The outer 1.5 mm or so are progressively darker but still sharp, and then there's a sharp cutoff.
I mention this because my lens covers a slightly larger circle than the SWC 38/4.5 Biogon, for which I've seen assertions that 80 mm is it. Mine differs from the SWC lens in having shorter outer barrels; the SWC lens' front and rear elements are inside their barrels, mine protrude about 4 mm. This makes me think that the SWC lens suffers a little from mount vignetting.
What this has to do with you is that the 75/4.5 Biogons I've seen have all had deep barrels like the SWC's 38/4.5. If you get one and its like that, you might risk having a machinist trim the barrels. They serve no structural purpose, seem to be as long as they are only to protect the front and rear elements.
I have a 75mm 4.5 and it is my favorite lens. However, every now and again, I will have to use my 90mm Super Angulon instead to get enough coverage. I usually try to use back movements when ever possible in focusing to stay within the image circle.
It is my understanding that stopping down doesn’t increase the size of the image circle but makes otherwise un-usable areas sharp enough to use.
That is not the problem with the Biogon. It goes from sharp to black almost instantly. I have mistakes with black corners to prove it. Further, in my opinion, it doesn’t need a center filter as I don’t notice significant fall off in illumination.
I don’t think it is “apples to apples” to compare it to other lenses with larger images circles that require center filters and where sharpness falls off near the edges, or that have to be stopped down significantly to get acceptable sharpness.
However, if you need a lens to do a lot of perspective correction (and you are not scanning your negatives, as I think one of the things Photoshop excels in, is perspective correction) run from this lens. I can usually get a little tilt and no rise. Or a little rise and no tilt, but a lot of one or two of anything will usually send me scampering for my 90mm.
<html>I used one of the surplus Biogons that was fitted to a Copal #1 shutter by Steve Grimes on a Graphic View camera and wasn't impressed. They were originally made for aerial photography on 5x5 film (I think). I had to remove the ground glass from the back of the camera to insert the rear element to the shutter as it wouldn't fit through the front of the camera. There didn't seem to be much movement available without vignetting and objects at the outside of the frame were distorted. I thought that using a lens with the history that these had was attractive but the weight, limits and the $1500. price that he was asking were too much for me. He thought the lens would cover 8x10 at minimum aperture but I can't see how.
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