Image circle too large?

[Theodoros]

I thought you would never ask. I do happen to have a 3" Biogon that FAPP does defeat the very most of optical vignetting, but to accomplish such it cheats by having a rear element larger than 4x5". Oh, on 8x10"? Don't ruin my day.

Call upon our theo/argen pair to put it through the mixmaster.
.

He isn't asking Jac... he is entering a further level in the conversation... I think I'll rest with my last post: "I think that if two lenses are mounted in different distance from the image area, then the proportion of image area to lens and lens to subject change (and thus DOF does) is far easier for one to understand... "

[Dan Fromm]

I thought you would never ask. I do happen to have a 3" Biogon that FAPP does defeat the very most of optical vignetting over 4x5", but to accomplish such it cheats by having a rear element larger than 4x5". Oh, on 8x10"? Don't ruin my day.

Call upon our theo/argen pair to put it through the mixmaster.
.

Interesting. My little 38/4.5 Biogons (remember, I've sold 18, still have 2) have rear elements that fit through a Century Graphic's lens throat. Yours must be a Pacific Optical version that wasn't made to the original prescription.

[Dan Fromm]

In the words of the Lord Protector, "I beseech you, in the bowels of Christ, think it possible that you may be mistaken."

[Argentum]

correct me if I'm wrong. Field of view (what is in front of the lens) is largely dictated by focal length. Angle of coverage(what is behind the lens) is largely dictated by lens design. The two are not necessarily similar angles.

[mingliaozi]

What if I use like a huge extension board? Like 50mm for example, or even 70?

[B.S.Kumar]

I'm sorry your relatively simple question got too technical, even for the most experienced amongst us

To get back on track, when you focus most lenses at infinity, the distance from the lensboard to the film plane will be approximately the focal length. A 90mm lens will be ~90mm away from the film plane, a 180mm lens ~180mm away, and so on. Some lenses are designed to focus at closer or longer distances than their focal lengths. This is common with lenses for rigid body cameras like 35mm or medium format, where the distance between the lens mount and the film or digital sensor is fixed.

You say your camera has a maximum extension of ~180mm. So it should focus at least to infinity. If your camera will not let you do this, or let you focus closer, use an extension board. We do this all the time when we want to use for example, a 360mm lens on a camera which has only a 350mm bellows, or when we want to focus closer than the bellows will allow.

Kumar

[Jac@stafford.net]

Interesting. My little 38/4.5 Biogons (remember, I've sold 18, still have 2) have rear elements that fit through a Century Graphic's lens throat. Yours must be a Pacific Optical version that wasn't made to the original prescription.

Twenty 38/4.5 Biogons!

Indeed, I was referring to the Pacific Optical 3". I don't need more than a couple. I just don't have that many doors in my little house. I would use bricks as door stops but the POs were easier to find here.

Picture of one mounted onto a 4x5 Sinar Alpa. And a picture of it with the camera bellows removed. Close up of rear element when focused to infinity.

Which brings us back to the subject. This is a 3" lens. Now, how does its physical dimensions fit the description of focal length given by B.S. Kumar? Remember, Kumar, this is a 4x5 camera.

[Dan Fromm]

I seen my opportunity and I took it.

[B.S.Kumar]

I would think that a 38mm Biogon, or a 3" Pacific Optical are some of the lenses not included in most people's definition of "most lenses" I must confess to never having seen either!

Kumar

[Argentum]

Well, it doesn't make any sense for them to design a lightweight compact camera that can't use a 90mm lens. I looked on B&H and they say the lens can be 50-125mm, so it appears around 90mm lens would be good. So, I guess more research is in order. Perhaps there are different versions.

I've seen somewhere else where it says 50-200mm so in answer to OP, yes a 90mm should be good for that camera.