Where on the infinity sign does infinity start on the distance mark?

Im using a rollei 35 so the distance between the corresponding aperture marks on the lens are quite close. Say I'm at f11 and want to use infinity on the far end. Do i place the middle of the infinity sign over the f11 mark or the beginning of the infinity sign over the f11 line? It looks like this would make a fair bit of difference to the closer edge of the DoF. What do you guys think?

dofmaster.com has some charts.

dofmaster.com has some charts.

 

 

Thanks Sanford.

 

What i really want to know is does infinity along the distance scale start at point A, B or C? I know im using the image of a leica lens but im asking generally [ or specifically to a rollei 35SE ;) ]

I have always assumed it is point B, which on a manual lens I align with the aperture indicator. Admittedly I tend to use a reasonably small aperture (F8 or smaller) to accommodate possible inaccuracies. Another approach is to set the lens to the hyperfocal distance for the aperture in use.

 

HTH

 

Tony

I'm leaning toward "C".

For a manual focus lens I simply put it all the way toward the infinity sign.

I have always assumed it is point B, which on a manual lens I align with the aperture indicator. Admittedly I tend to use a reasonably small aperture (F8 or smaller) to accommodate possible inaccuracies. Another approach is to set the lens to the hyperfocal distance for the aperture in use.

 

HTH

 

Tony

 

 

Ok, so im a little confused by Hyperfocal distance because frim my reading, this is just the distance of critical focus where infinity is set at one of the aperture markers for the used aperture. So in the case of this example image below, When using f22, the hyperfocal distance is something like 9m/28 feet. Right?

 

http://www.fineart-photography.com/dof_focus.jpg

For a manual focus lens I simply put it all the way toward the infinity sign.

 

I don't understand what you mean Bebu

Try this website :

 

How to Find and Use Hyperfocal Distance for Sharp Backgrounds

 

Tony

I don't understand what you mean Bebu

 

Turn the focusing ring toward the infinity sign until you can't turn it any more. I do this for manual focus lens as AF lenses you can turn the ring either pass infinity a little bit or you can turn the ring forever as it doesn't have a hard stop.

In optics like camera lenses, optical infinity is usually defined as 1000x the focal length of the lens. So if you think about it, real infinity (or what you might focus on in the distant horizon) is often quite a bit away from optical infinity, the slack being taken up by DOF, and the fact that you can't focus a normal lens in fine enough increments at very long distances to really make a difference between optical infinity and that long distance. So, back to your original question...it probably doesn't make a difference when focusing beyond a couple of feet whether you use point B or C as your reference for infinity. The way you can check, of course, is with an object at optical infinity and a ground glass with a loupe at the focal plane, and three observations at points A,B and C on your infinity scale. Different manufacturers probably use different tolerance levels. As I frequently use rangefinder cameras, I calibrate my infinity focus at about 1/2 mile.

RTFM.

RTFM.

 

Return To Foreign Manufacturer ?

This is complicated. Not all lenses have a hard infinity stop. - Soviet 1000mm cassegrains don't (to allow for focal length change due to camera temperature shift).

Question #2: For what use case was your DOF ring painted / chart printed and WTF are you trying to achieve? - DOF is defined as a still bearable size of the circle of confusion. I assume it makes a difference if you take postcard sized newspaper printed shots or blow the highest resolution sensors' or films up to billboard size...

If I had a tripod and wanted a sharp background in a poster, I would not neccessarily trust a DOF engraving to work for me; i.e. I'd maybe use your point "C" or set f11 and the hyperfocal distance for f8, or worrying about diffraction use f8 and the f5.6 markings.

Loading TriX, risking camera shake and shooting for post cards I'd stick with point B maybe even A if the background isn't that important.

On a well made lens with hard stop I'd look which bit of infinity the absolute focus marker is pointing at and use that. - Between A & B on the shwn picture (assuming the lens hits it's hard stop).

As Jochen said it will vary with temperature (not so much with a 50mm as with a 1000mm but still vary)

It's probably intended to be the centre of the symbol (point B) but if using the lens makings to give DOF I'd work to C, unless conditions won't allow that. You may waste a little of the potential DOF but you'll get a better focused infinity.

 

If focusing on stars I'd ignore the scale altogether & work with the magnified image (Ideally with a focusing mask). Getting stars pin sharp is a lot harder than theory would suggest!

 

Of course there's every bit as much imprecision on where the other numbers are taken as.

My Hyperfocal Pro app suggests a hyperfocal focus distance for the Rollei's 40mm lens at f/11 on 35mm film as 16.25 feet. (Hence the choice of various versions with 15 foot and 20 foot focus scales.) This puts the near limit of "focus" at 8.3 feet, and the far limit at infinity. Depending on your subject and composition, you can fudge this a bit. Let's be absolutely clear, the accuracy of the Rollei's focus scale is not very good, and, depending on the version, may only give two or three marked positions plus infinity. This implies the camera is expected to be used with three basic focus zones. The first is quite close, in the 2'-8' zone. The second is mid-distance, from about 8'-15' or so. The third is in the hyperfocal zone, at 15' to infinity. The camera is not designed or intended for a more detailed evaluation of focus distance. By way of contrast, my Micro-Nikkor 55mm/2.8 Ai has a vast and widely spaced distance scale, because it is intended to be used in a very finite and focus-sensitive application.

 

What you can learn from a program like Hyperfocal Pro or similar is where the best focus range is to obtain your desired results. In regards your specific question: On your camera, at f/11 I would start somewhere between the largest marked focus distance and position "A" (the value of the largest number will vary with version) and then try minor shifts to A, then B, then C, and evaluate the results. Keep in mind you're asking for an answer at a level of detail your camera likely does not support. If the lens has a hard stop at infinity then that's a good place to start for subjects over about 30-35 feet away. Otherwise, a focus distance of about 17 feet will give in-focus results from about 8 feet to infinity. A focus distance (at f/11) of less than 16 feet will start to blur the background, while pushing the focus distance out to 20+ feet will push the zone of acceptable focus further from the camera. Again, what is acceptable will depend on many factors. For people, err on the close focus side. For landscapes, go to hyperfocal distance or further towards infinity. (It will be hard to go wrong at position "A", unless you need sharp foreground.) And, don't expect more from your camera than it has to give.

Edited February 19, 2019 by DavidTriplett

The index of infinity is at the center of the symbol, where the lines cross (position B). That said, there are other considerations.

 

Most lenses will focus a little beyond infinity, in order to allow for the change in focal length with temperature, and manufacturing variations. Manual lenses for film cameras generally stop right on the mark. The small shift in focus seldom mattered until high-resolution digital cameras were invented. My Zeiss Loxia lenses must be backed off a little from the mark (and stop) when focusing on distant objects (including stars). AF lenses focus considerably beyond infinity, for all of the above reasons, and to accommodate feedback control.

 

Depth of field is a convenient fiction. There is only one plane of focus. DOF limits are based on "acceptable" amounts of focus blur, which may vary according to the degree of enlargement, your taste, and the subject matter. I tend to focus on the key object in the composition, whether in the foreground, mid ground, or the horizon. In extreme cases, I take multiple exposures at varying focus, and stack the results. That's possible with film, but rather costly.

 

Markings on TLR cameras are very close together, and there is generally a lot of slop in the settings (I have a Rollei E2). Try to err in the direction which would render your principal subject layer in the best focus.

Manual lenses for film cameras generally stop right on the mark. The small shift in focus seldom mattered until high-resolution digital cameras were invented.

 

Even at that, a significant portion of fast(er) long manual focus lenses will focus past infinity as things like thermal expansion CAN add up to appreciably throw off the focus of these lenses. My old FD mount 400mm f/4.5(that I no longer have) had a line about 1/4" wide to represent infinity, and I WOULD see infinity drift if I was using it in the sun and the lens heated up.

 

Canon started using fluorite for super-teles in the 1970s, and found that they were especially susceptible. The first fluorite lenses were painted black, just like all other lenses, but the white paint that's now a Canon "signature" was supposedly to minimize how much the lens would heat up in the sun(the 400mm I mentioned above was not an L lens, which in those days meant it used only conventional spherical glass elements, and was also painted gloss black). I don't know whether or not this was all marketing hype or not-I've never used a Canon pre-L Fluorite lens. Also, it's worth mentioning that Nikon is now using fluorite in some of their fast tele-zooms and super teles, and the Nikon "FL" lenses are black just like pretty much every other Nikkor made in the past 60 years.

Depth of field is a convenient fiction. There is only one plane of focus. DOF limits are based on "acceptable" amounts of focus blur, which may vary according to the degree of enlargement, your taste, and the subject matter.

+1 to this. However, I expect the "acceptable" amount of focus blur for the Rollei will cover a much larger apparent DoF than one would accept or expect in a higher end camera/lens combination. Let's keep in mind the OP's stated paradigm.

Markings on TLR cameras are very close together, and there is generally a lot of slop in the settings (I have a Rollei E2). Try to err in the direction which would render your principal subject layer in the best focus.

This restates the gist of my recommendations.

Never thought about it before but I figure turning the lens all the way until it stops is the correct spot. On my Leica it stops at the "B" location and when looking into the viewfinder the focusing spot lines up perfectly with a distant subject.

Sorry for the repeats. I think I phrased things differently, and meant no criticism. I'm just gabby during breaks editing 8 hours of video.

 

Zeiss Batis lenses have an OLED display in lieu of distance and DOF markings. The focus ring turns freely without stops. You can set infinity (e.g., for astronomy) if your turn the ring until infinity just appears, back and forth a couple of times to confirm the position, and you're good to go. It does not seem to be temperature dependent. Stars I like to shoot are mostly too dim to see in the viewfinder.

"Depth of field is a convenient fiction. There is only one plane of focus."

 

Correct. But as I recall, DOF doesn't mean that a whole range is in focus. But it describes basically a range that is seen more or less in focus. Circles of Confusion Think of it as a working approximation that works better on some lenses than others.

Edited February 20, 2019 by Uhooru

The generally accepted definition of depth of field is fairly precise - a circle of confusion of 0.25 mm in an 8"x10" print, viewed at a distance of 10". That is approximately the limit of resolution for an average human eye.

Per Wiki, " In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. ... In photography, the circle of confusion (CoC) is used to determine the depth of field, the part of an image that is acceptably sharp." You are talking at the sharpest accuracy, but misses the point because DOF is concerned with the range of acceptable sharpness.