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LFLarry
24-Aug-2020, 11:31
I want to make sure I fully understand how to determine infinity for all of my various large format lenses.

I assume that I will need to know the flange focal distance for the lens and then from there, I really don't know how to use that information to determine infinity for each lens. I have both standard and telephoto lenses, so I am hopeful that someone here will teach me how to do this properly.

Thanks in advance for teaching an old guy something new today.

Larry

Merg Ross
24-Aug-2020, 12:07
https://www.largeformatphotography.info/forum/archive/index.php/t-39732.html

Bob Salomon
24-Aug-2020, 12:15
You have properly cut cams, the infinity stops and focusing scales for your Technika?

Oren Grad
24-Aug-2020, 12:16
Not clear what you're asking. Are you trying to determine how far a target has to be for it to be a reasonable proxy for infinity when you are calibrating a rangefinder? If not, what exactly are you trying to understand?

LFLarry
24-Aug-2020, 12:25
Hi Bob. Yes, I have a properly cut cam for my lens.

I know the default answer is to send the camera to an authorized service center for setup and calibration, but I simply don't have months to wait, so I want to at least try and understand what is involved so I can make an educated attempt at trying to setup my lens on my Master Technika.

I believe the first step is to set the lens at infinity and that is what I am asking the original question, but I want to make sure I know what that means so I start off with the lens in the right place on the rails.

Any pointers are much appreciated.



You have properly cut cams, the infinity stops and focusing scales for your Technika?

Tin Can
24-Aug-2020, 12:28
If focusing on a billboard a mile distant and setting infinity there is not good enough, you are taking pictures of satellites, or moons

It is not significant, meaning you will not see a difference

Set infinity STOPS for something you shoot, like trees, mountains, moons

LFLarry
24-Aug-2020, 12:58
Thank you.


If focusing on a billboard a mile distant and setting infinity there is not good enough, you are taking pictures of satellites, or moons

It is not significant, meaning you will not see a difference

Set infinity STOPS for something you shoot, like trees, mountains, moons

Bob Salomon
24-Aug-2020, 13:29
Hi Bob. Yes, I have a properly cut cam for my lens.

I know the default answer is to send the camera to an authorized service center for setup and calibration, but I simply don't have months to wait, so I want to at least try and understand what is involved so I can make an educated attempt at trying to setup my lens on my Master Technika.

I believe the first step is to set the lens at infinity and that is what I am asking the original question, but I want to make sure I know what that means so I start off with the lens in the right place on the rails.

Any pointers are much appreciated.

Presuming your cam has the same serial number as your lens you install the cam. Focus on something several hundred yards from you. Marflex used a telephone pole and wires across the street from our offices. Focus through the gg till the wires and pole are as sharp as possible. Then look through the rangefinder to see if it agrees with the gg.
If yes, carefully install the infinity stops against the front standard, carefully because the screws that fasten the stops have sharp pointed screws that will dig into the chrome plated focus tracks. If the stops are moved those screws will leave small pit marks in the tracks that can not be removed.
If no your cam is not cut for your lens.
When one buys a new cammed lens from the factory or the distributor the lens box comes with the stops and the focusing scale for the bed. Along with these you also get a cardboard tube that contains a focusing target and instructions. These items let you properly install the infinity stops at the proper position on the tracks when viewed from about 5 meters on the gg.

It isn’t quite as simple as it would appear at first glance.

Why would it take months to properly adjust your camera?

Corran
24-Aug-2020, 13:34
If you have the Technika, cams, and lens, first get the lens on the camera and pull the front standard out to middle of the rail (if you have a wide-angle that needs to have the rail pushed back or a telephoto with it moved forward on the extension, set it as such).

Next, focus in the rangefinder on a very clear target at close to infinity. For the purpose of infinity, anything farther than a couple hundred feet is fine, you aren't going to be able to discern anything past that in the RF. After that is set, lock the focus.

Then, put the infinity stops on the camera and let them move freely on the rail with the tabs flipped up. Move the lens on the rail till it is in focus on the ground glass. Snug up the infinity stops and tighten them down slightly.

Now focus on something about 25 feet away. Check and see if the RF and GG match up. If not, you may want to move the stops till it is, and focus on infinity second - choose whatever works best for your shooting style, but most likely they will both be in focus at all ranges unless you have something seriously wrong with the camera, lens, or cam. Once you are satisfied, you can tighten down the stops more tightly. They can move from the impact of the front standard if not tightened enough.

You shouldn't need the factory to do this. I've done it, even with mismatched cams/lenses which often are "close enough" for most situations.

LFLarry
24-Aug-2020, 17:03
Hi Bob, I was able to get the cam and lens all setup and everything works perfectly. I even exposed a couple sheets of film to confirm. I am super happy about this!

In regard to the couple of months comment, that is the time it would take to ship the camera, wait for it to be serviced and then return shipped. Now I don't have to wait for any of this!!

Thanks again.





Presuming your cam has the same serial number as your lens you install the cam. Focus on something several hundred yards from you. Marflex used a telephone pole and wires across the street from our offices. Focus through the gg till the wires and pole are as sharp as possible. Then look through the rangefinder to see if it agrees with the gg.
If yes, carefully install the infinity stops against the front standard, carefully because the screws that fasten the stops have sharp pointed screws that will dig into the chrome plated focus tracks. If the stops are moved those screws will leave small pit marks in the tracks that can not be removed.
If no your cam is not cut for your lens.
When one buys a new cammed lens from the factory or the distributor the lens box comes with the stops and the focusing scale for the bed. Along with these you also get a cardboard tube that contains a focusing target and instructions. These items let you properly install the infinity stops at the proper position on the tracks when viewed from about 5 meters on the gg.

It isn’t quite as simple as it would appear at first glance.

Why would it take months to properly adjust your camera?

LFLarry
24-Aug-2020, 17:06
Thanks Corran. I was able to get this all setup today! I do have a mismatched cam and it works great. I even exposed and developed a couple sheets of film to confirm what I was seeing in the rangefinder and on the ground glass. Thanks for your detailed reply and help!



If you have the Technika, cams, and lens, first get the lens on the camera and pull the front standard out to middle of the rail (if you have a wide-angle that needs to have the rail pushed back or a telephoto with it moved forward on the extension, set it as such).

Next, focus in the rangefinder on a very clear target at close to infinity. For the purpose of infinity, anything farther than a couple hundred feet is fine, you aren't going to be able to discern anything past that in the RF. After that is set, lock the focus.

Then, put the infinity stops on the camera and let them move freely on the rail with the tabs flipped up. Move the lens on the rail till it is in focus on the ground glass. Snug up the infinity stops and tighten them down slightly.

Now focus on something about 25 feet away. Check and see if the RF and GG match up. If not, you may want to move the stops till it is, and focus on infinity second - choose whatever works best for your shooting style, but most likely they will both be in focus at all ranges unless you have something seriously wrong with the camera, lens, or cam. Once you are satisfied, you can tighten down the stops more tightly. They can move from the impact of the front standard if not tightened enough.

You shouldn't need the factory to do this. I've done it, even with mismatched cams/lenses which often are "close enough" for most situations.

Bob Salomon
24-Aug-2020, 17:45
Thanks Corran. I was able to get this all setup today! I do have a mismatched cam and it works great. I even exposed and developed a couple sheets of film to confirm what I was seeing in the rangefinder and on the ground glass. Thanks for your detailed reply and help!

What happens when you focus at other then infinity?

Daniel Casper Lohenstein
24-Aug-2020, 21:15
Hi Bob. Yes, I have a properly cut cam for my lens.

I know the default answer is to send the camera to an authorized service center for setup and calibration, but I simply don't have months to wait, so I want to at least try and understand what is involved so I can make an educated attempt at trying to setup my lens on my Master Technika.

I believe the first step is to set the lens at infinity and that is what I am asking the original question, but I want to make sure I know what that means so I start off with the lens in the right place on the rails.

Any pointers are much appreciated.


You can buy new cams and sharpen them yourself. I would prefer this solution. You don't have to "adjust" anything. You build yourself the cams you need, depending on the things you focus. You only need a file and a vice.

Tschau zäme

LFLarry
25-Aug-2020, 04:21
Hi Bob, it works perfectly at all distances. I shot 3 sheets of film to confirm. 1 at infinity, 1 at about 100 ft. and 1 at about 25 ft. All three were tack sharp on the film as they were on the ground glass and in the rangefinder.



What happens when you focus at other then infinity?

LFLarry
25-Aug-2020, 04:22
Any tips or insights into how to go about doing this?


You can buy new cams and sharpen them yourself. I would prefer this solution. You don't have to "adjust" anything. You build yourself the cams you need, depending on the things you focus. You only need a file and a vice.

Tschau zäme

Daniel Casper Lohenstein
25-Aug-2020, 04:32
Hi Bob, it works perfectly at all distances. I shot 3 sheets of film to confirm. 1 at infinity, 1 at about 100 ft. and 1 at about 25 ft. All three were tack sharp on the film as they were on the ground glass and in the rangefinder.


Any tips or insights into how to go about doing this?

Well, if your cams are tack sharp, everything is fine.

Otherwise, I imagine that you mount a new cam, focus on the ground glass at a certain distance, 1m, with an aperture of 5.6, and then check whether the range finder is also sharp. If not, move the cam to see if something is missing (bad luck) or if there is too much on it. If there is too much, file it off carefully, but only at the region where the focusing slider bottom bolt touches the cam.

This again is done successively for all distances, I think. I suggest not to finish the near point right away, but to file the near and far point and the middle evenly. This way you should slowly approach a sharpness in all areas. It surely takes time and requires intuition. Maybe that's why this is something that is done in the factory, by trained specialists. You don't tune pianos yourself, do you?

Infinity at 5.6 and 150mm is assumed at about 24m, because of the hyperfocal distance at about 47m, given 0.086mm as circle of confusion at 30cm print width and 35cm viewing distance. 100cm print width at 35cm viewing distance gives 0.026mm as circle of confusion. Then everything will be sharp at 5,6 at 78m, with a hyperfocal distance of 156m. Cf.http://www.erik-krause.de/schaerfe.htm#top Correct me if I get it wrong

reddesert
25-Aug-2020, 11:47
Infinity at 5.6 and 150mm is assumed at about 24m, because of the hyperfocal distance at about 47m, given 0.086mm as circle of confusion at 30cm print width and 35cm viewing distance. 100cm print width at 35cm viewing distance gives 0.026mm as circle of confusion. Then everything will be sharp at 5,6 at 78m, with a hyperfocal distance of 156m. Cf.http://www.erik-krause.de/schaerfe.htm#top Correct me if I get it wrong

This is the second time you've said something like "Infinity at 5.6 and 150mm is assumed at about 24m, because of the hyperfocal distance at about 47m," and I think that's misleading. 24m would be the near limit of acceptable focus when focused at the hyperfocal distance, not when focused at true infinity.

Infinity is still at true infinity. Infinity (or really, something far away, like 100+ meters) is used to calibrate focusing systems because there's no question about where it is, and because it's one limit of the travel of the focusing system. Also, it often appears in photographs as the background. If you only use a rangefinder at 2-10 meters then you should certainly calibrate the rangefinder there, but I think it will generally be easier to calibrate a rangefinder by getting it correct at infinity first.

Corran
25-Aug-2020, 12:05
Yes!

A good RF like the Linhof should be perfectly in focus at the point where you focused at the widest aperture of the lens. Not fudged for "hyperfocal" and/or "good enough" focus for f/22.

Daniel Casper Lohenstein
25-Aug-2020, 23:26
This is the second time you've said something like "Infinity at 5.6 and 150mm is assumed at about 24m, because of the hyperfocal distance at about 47m," and I think that's misleading. 24m would be the near limit of acceptable focus when focused at the hyperfocal distance, not when focused at true infinity.

Infinity is still at true infinity. Infinity (or really, something far away, like 100+ meters) is used to calibrate focusing systems because there's no question about where it is, and because it's one limit of the travel of the focusing system. Also, it often appears in photographs as the background. If you only use a rangefinder at 2-10 meters then you should certainly calibrate the rangefinder there, but I think it will generally be easier to calibrate a rangefinder by getting it correct at infinity first.


Yes!

A good RF like the Linhof should be perfectly in focus at the point where you focused at the widest aperture of the lens. Not fudged for "hyperfocal" and/or "good enough" focus for f/22.

That's a good point (whereas the circle of confusion and the print size / viewing distance play an important role).

But what do you "see" on your tiny ground glass? Every far away positioned object behind the near border will appear sharp, so "true" infinity (what's that?) is no longer recognizable.

Why do I mention this again and again? I don't know what kind of Linhof Technika the OP has. Eg. the Linhof Technika IV is not "zeroed".

BTW the problem is not solved by turning the focusing rail back to zero. You also have to find the zero position of the front standard, which you then fix with the infinity stops. And here the near limit problem plays again an important role.

Do you really know for sure which specification Linhof has for "infinity"? Do you think they focus on the spires of the Frauenkirche in Munich? They've got specs and devices. As long as you don't know the specs you can't "adjust" anything. Inevitability and uniqueness or unique features are part of successful commercial thinking.

As you say we want to take pictures in the range of 1-5m with the range finder. For infinity (landscape, architecture) we don't need a range finder. - Personally, I think a range finder has to work in a close range. There will be near range deviation if you make wrong far distance adjustments, because the depth of field becomes shallower, especially with larger apertures. Therefore a good calibration in the close range seems to be reasonable.

You're right, Corran: after all, it's about focusing with 5.6/135mm in the group range and 5.6 / 210mm in the portrait range - otherwise what's the point of having a 10k$ high-performance precision device like a range finder Technika?

Tschau zäme

reddesert
26-Aug-2020, 10:54
I don't really understand what the argument is here.

To set the infinity stops, Linhof doesn't focus on the Frauenkirche. They presumably use an autocollimator to produce a virtual target at infinity. Most of us don't have an autocollimator (although there is a Rick Oleson article about using an SLR to imitate one, if you have an SLR whose focus is known good). Without one, you can start by focusing a faraway target on the ground glass, like a utility pole, a streetlight, or the Frauenkirche. You focus back and forth to find the best focus, as with any target. It doesn't matter that the focus is "acceptable" at the near distance - you're finding the best focus. Now you know the location of infinity for that lens, so you know where to put the infinity stop.

After that, you can proceed to focus at some other distance, say 2 meters, and check between the ground glass and the rangefinder.

The problem with trying to start at 2 meters is measuring 2 meters from what? From the lens, the film plane, or some property of the lens like the front principal plane? I don't know exactly what the camera maker measured when they engraved the focus scale. However, the camera maker and I can agree on infinity.

Havoc
26-Aug-2020, 10:59
The problem with trying to start at 2 meters is measuring 2 meters from what? From the lens, the film plane, or some property of the lens like the front principal plane? I don't know exactly what the camera maker measured when they engraved the focus scale. However, the camera maker and I can agree on infinity.

Well, normally you measure from the film plane. 35mm SLR's (digital and film) all (AFAIK) have a mark on their body indicating the film plane. Looks like a sort of plimsoll mark on top of the body.

Bob Salomon
26-Aug-2020, 11:03
I don't really understand what the argument is here.

To set the infinity stops, Linhof doesn't focus on the Frauenkirche. They presumably use an autocollimator to produce a virtual target at infinity. Most of us don't have an autocollimator (although there is a Rick Oleson article about using an SLR to imitate one, if you have an SLR whose focus is known good). Without one, you can start by focusing a faraway target on the ground glass, like a utility pole, a streetlight, or the Frauenkirche. You focus back and forth to find the best focus, as with any target. It doesn't matter that the focus is "acceptable" at the near distance - you're finding the best focus. Now you know the location of infinity for that lens, so you know where to put the infinity stop.

After that, you can proceed to focus at some other distance, say 2 meters, and check between the ground glass and the rangefinder.

The problem with trying to start at 2 meters is measuring 2 meters from what? From the lens, the film plane, or some property of the lens like the front principal plane? I don't know exactly what the camera maker measured when they engraved the focus scale. However, the camera maker and I can agree on infinity.

LInhof has an indicator on its back frame that indicates the film plane position.

Daniel Casper Lohenstein
26-Aug-2020, 11:18
The problem with trying to start at 2 meters is measuring 2 meters from what? From the lens, the film plane, or some property of the lens like the front principal plane? I don't know exactly what the camera maker measured when they engraved the focus scale. However, the camera maker and I can agree on infinity.

f5.6, 150mm, circle of confusion some mediocre 0.089mm, distance aperture to object 2,00m, bellows extension 12.162mm, distance film plane to object 2,16m. http://www.erik-krause.de/schaerfe.htm#top The distance film plane to object seems to be reliable, since the often belittled, because expensive Technika has a dedicated film plane indicator on the top of the technical back, as others mentioned quicker than me. At 1,18m your calibration will be even more exact with only 3cm dof and fit the 1m indication on your distance scale. If the closer range is right, and if the cam matches both the lens and the camera, we don't even have to think about infinity anymore, in my opinion, but i am not a camera builder. But this is how I "adjusted" the Horseman 985 6x9 with 4 cams and their matching Topcor lenses. Btw. every bigger stroke brings the Horseman range finder out of alignment - so it is useful to know how to adjust it yourself. - On the other hand your Linhof works with reliable precision even under the toughest conditions.

Good luck!

Tin Can
26-Aug-2020, 15:25
Since the thread title does not specify Brand, I post this link, I have fooled with this manytimes

Adjusting the Kalart Rangefinder (https://www.graflex.org/speed-graphic/kalart-adjustment.html)

My best usable RF finder is the one one I put a laser inside, but that's an old thread

johnj88
15-Dec-2020, 20:09
Related but can someone help me understand where to pull the front standard out to?
Sorry basic question I know.

I don’t really understand.
The very earliest is for wide angle, as it denotes 90mm
The middle says 180mm
Then the very front says 135mm

If I have a 210mm lens where do I put it?
I tried to read the manual but it didn’t really do a good job of explaining.

210631210631

Corran
15-Dec-2020, 20:55
The distance markings are designed to work with that little arrow indicator / black triangle when the lens is set to infinity at "stops" that you must be missing. Ignore them, especially since you aren't using those lenses. Set your camera up on a tripod with the focus racked all the way back and locked, with the sliding extension at the normal, not extended or retracted (like in your picture) position. Simply move the front standard till "infinity" is in focus, and there is your infinity position, roughly. If you want you can use a marker to add a mark to the bed of the camera. I would fudge it a little in towards the body so that you are past infinity, so you have some room to focus to infinity.

Also don't forget that unless you are using the RF this really doesn't matter much as long as you aren't wildly out of position. When I shoot my Linhof MT for landscape I just pull the lens out till it's kinda almost in focus and then use the focus knob to get it in focus.

PS: you should probably find an old Technika users manual online and read it, and then simply practice with your camera. It's not a complex camera, but if you don't understand all of the extensions and accessories and etc., especially if you are a new LF user, it might be daunting. The manual should from the Technika IV, V, or Master models will work fine - you have one of those models it looks like to me.