There is nothing more annoying to me than purchasing a cheap wide angle lens (prime or zoom) whereby infinity is 'not quite' there. It is almost as if the manufacturer is depending upon depth of field to make up for the lack. I go to work, immediately, and have never had regrets in doing so. Let's face it, we NEVER shoot at infinity, anyway, Not even the moon is infinity. - David LygaThat's fully justified especially with longer or zoom lenses where part of the design allow for expansion of the glass.
I think it's less important shith shorter lenses because of a less magnified image on the GG.
Excellent and needed point. With SLRs, if it is in focus at one distance, it is in focus at ALL distances. That is the beauty of "Single Lens" reflex technology. Not necessarily so with rangefinders, which give you theoretical information, not real time information. The RF mechanism is quite accurate, but short of the real time info given on an SLR. To compound matters, a range focus camera, where one sets the focus as per the focus scale, can be quite inaccurate, especially at the closest distances.I've done this with Zeiss folders I've repaired and it works. A word of warning, though, just because the indicator for infinity is set, doesn't mean that the closer markings are accurate. With the folders I've fixed, I also shoot a roll to test at ten feet focus; set a target accurately from the camera and shoot at several different markings near 10 feet on the focus ring, then examine the negs at 20X. There can be a significant difference. I make a mark on the ring if needed.
Mess Ikontas can be even worse, I always test for 10' focus, then set the uncoupled rangefinder to that setting, regardless of where the focus ring is.
Never had that problem with my coupled Super Ikontas.
No, you might have misinterpreted. If I recalibrate a lens so that it focuses a tiny bit past infinity, there will be no misfocus because the viewfinder of an SLR will indicate such misfocus just as readily as if I had not done that. Maybe you are thinking of an rangefinder camera, but even still, the RF mechanism would indicate that the rear element was a tiny bit too close to the film plane to be focused properly at infinity. The mechanism would indicate, by closeness to the film plane, whether the image is being recorded in focus or not. - David LygaFocus past infinity is the worst thing one could possible do. It will ensure absolutely NOTHING is in focus.
With an accurate SLR, its focusing scale is of little importance. With a dead accurate RF camera its focusing scale is of little importance (because the viewfinder will tell you what is in focus). With a scale-focus based camera, it pays to check that scale at both infinity and at closest distance. Why? Because if there is an error at either or both ends, one must superimpose an accurate scale onto the pre-existing one so that future errors will not manifest.Hmm. Cine lenses' focusing scales are precise. Exact. Not fudged in either direction. They're sometimes focused by tape measure instead of through the lens.
David, I think you equivocated. Setting the far focusing distance stop so that a lens can be focused through infinity is one thing. Adjusting the focusing scale so that it is inaccurate is another. My 700/8 Questar's far focusing stop is past marked infinity. When the lens hasn't sat baking in the sun, the infinity mark and all closer distance marks are right.
I collimate the other way. Just barely in front of infinity by a micron or so. If I collimated past infinity, I'd be afraid to accidentally bump the focus ring to the far stop or not see the focus correctly, in which case NOTHING will be in focus. There cannot be a focused image when the lens is closer to the film than it's focal length, and that is what one would be doing when focusing beyond infinity.No, you might have misinterpreted. If I recalibrate a lens so that it focuses a tiny bit past infinity, there will be no misfocus because the viewfinder of an SLR will indicate such misfocus just as readily as if I had not done that. Maybe you are thinking of an rangefinder camera, but even still, the RF mechanism would indicate that the rear element was a tiny bit too close to the film plane to be focused properly at infinity. The mechanism would indicate, by closeness to the film plane, whether the image is being recorded in focus or not. - David Lyga
Your explanation is for SCALE FOCUS cameras. In the case of the SLR, a tiny bit past infinity is actually a slight improvement, as oftentimes we focus most accurately by a 'back and forth' jockeying of the focus ring, zeroing onto the precise focus. And, if a RF camera's rangefinder is dead accurate, the same thing can be handily done. However, with SCALE ONLY cameras, we MUST depend upon a dead accurate scale focus, and it is immaterial whether that scale is the manufacturer's or one we have superimposed onto the manufacturer's scale (in order to increase focus accuracy). In THAT case, with scale focus only cameras, it does not pay to attempt a focus point that is slightly beyond infinity. There would be no purpose, only confusion. Indeed, a precise infinity should be the ultimate stop on that scale focus focus ring. - David LygaI collimate the other way. Just barely in front of infinity by a micron or so. If I collimated past infinity, I'd be afraid to accidentally bump the focus ring to the far stop or not see the focus correctly, in which case NOTHING will be in focus. There cannot be a focused image when the lens is closer to the film than it's focal length, and that is what one would be doing when focusing beyond infinity.
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