HELP how to focus

[beemermark]

OK this isn't a newbie question but I just had Lasik surgery in one eye and now don't know which eye to use to focus on the ground glass.

I've had 20/200 vision all my life (I'm 57). Of course once I got past 40 I developed presbyopia. Being near sighted I could remove my glasses and see fine for a distance of about 3~5 feet. Of course I had to wear progressive bifocals to correct my near sight with close to plain glass in the bottom to see up close.

So now I just had one eye corrected for far vision. So one eye can see 20/20 for anything over 5 feet and nothing under 5 feet. The other eye can only see things 5 feet or closer. They call it mono-vision and amazingly it works well. With both eyes I have 20/40 vision which is a huge improvement.

Anyway I went out with my 5x7 and when I went to focus I found I can focus with either eye. Of course I'm not ending up with the lens at the same focus point.

SO WHICH EYE DO I USE??

TIA

[Ron Marshall]

Use the eye that is good at near distances, since you must clearly resolve the image on the ground glass, regardless of which distance you want to be in focus.

[Joanna Carter]

Anyway I went out with my 5x7 and when I went to focus I found I can focus with either eye. Of course I'm not ending up with the lens at the same focus point.
Think about it... Most lupes have focus adjustment, therefore, it is usually possible to focus with most visions, adjusting the lupe to suit. Don't forget, you are not focusing your eye on the subject of the image, you are simply focusing on the image on the GG screen.

[aduncanson]

If stereo vision proves to be important you could have an optometrist make you a special pair of glasses that would correct both eyes to focus at some comfortable near distance for focusing and composing. (I like a focus distance a little more than the diagonal of my camera's format, but I can buy mine at the drugstore.) The two lenses would be very different and the glasses would be for special purposes only.

[beemermark]

The answer is I need to focus on the GG. I kind of thought so but I wasn't sure. Since only one eye uses the loupe I'll use the eye that's good for near vision.

THANKS

[GPS]

You can use whatever eye you want to- but with a different adjustment of your loupe.

[Leonard Evens]

OK this isn't a newbie question but I just had Lasik surgery in one eye and now don't know which eye to use to focus on the ground glass.

I've had 20/200 vision all my life (I'm 57). Of course once I got past 40 I developed presbyopia. Being near sighted I could remove my glasses and see fine for a distance of about 3~5 feet. Of course I had to wear progressive bifocals to correct my near sight with close to plain glass in the bottom to see up close.

So now I just had one eye corrected for far vision. So one eye can see 20/20 for anything over 5 feet and nothing under 5 feet. The other eye can only see things 5 feet or closer. They call it mono-vision and amazingly it works well. With both eyes I have 20/40 vision which is a huge improvement.

Anyway I went out with my 5x7 and when I went to focus I found I can focus with either eye. Of course I'm not ending up with the lens at the same focus point.

SO WHICH EYE DO I USE??

TIA

You should probably use the uncorrected eye, but it is a bit more complicated than that. You should probably also get a 4 X loupe to help you focus, and you might want to get a magnifier which will allow you to scan the entire scene from about 8 inches.

There are two issues here.

For evaluating the scene, you should put your eye at about the diagonal of the format from the ground glass. I don't have a 5 x 7 to measure, but I would guess that would be about 8 inches. If you can get that close with your uncorrected eye, then use it for framing and generally evaluating the scene. If not, you would need some sort of magnifier or special glasses. (A loupe usually won't work for this because it has too narrow a view.) Viewing the scene with the proper perspective is often ignored, and I find it helps me enormously to do it.

For focusing, on the other hand, you should put your eye closer to the ground glass, and I would doubt that you can get it close enough on the basis of what you say. A loupe lets you in effect put your eye closer, so in principle you should use as powerful a loupe as you can find. But if the loupe is too powerful, you won't be able to distinguish surface features of the focusing screen from the image. The usual advice is not to go much higher than 4 X, and for many purposes 2 X will suffice.

Young people with normal vision usually are comfortable looking at something from 10 to 12 inches away and need help to get closer. A 2 X loupe would put such a person at about 5-6 inches and a 4 X loupe at half of that. At your age, with presbyopia, you can't even get that close with your 20/20 eye. If your other eye is near-sighted enough, you may be able to get that close without a loupe, but as I said above, I doubt it. So you may want to get a loupe to help you focus.

Before I had my cataracts removed, I was extremely nearsighted and could get to within an inch or so of the gg, which was a big help in focusing. Now I have close to 20-20 vision in both eyes, but I can't see anything clearly closer than four feet or more. So I've had special glasses made which allow me to put my eyes at about 6 inches from the ground glass, which is just about right for general viewing for my 4 x 5. It is also equivalent roughly to a 2 X loupe.

You might benefit by studying the lfphoto web page which has an extensive discussion of focusing. I use the near point, far point method of focusing which works a follows. I focus first on the furthest point I want sharp in my image and then on the closest, and I note the positions of the rail where those points come to focus. I then focus halfway in between them on the rail. this way I get close enough that I can just use my (2 X equivalent) glasses. With this method getting the focus exactly right is not as crucial. But were i to use my regular bifocals, I would still be 12-14 inches away, and I wouldn't be able to see detail well enough to focus critically.

If you used this method, you might find you did well enough with your eye at about 8 inches, so you could do both things at once, evaluate the scene and focus, but I suspect you would also need a loupe for focusing.

I choose my f-stop on the basis of the distance along the rail between those points, which is called the focus spread. But one fairly simple rule of thumb for 5 x 7 might be to take the focus spread in mm, multiply it by 10 and then take 3/8 ths of that to get the f-number you should use.

For example, suppose your focus spread is 8 mm, Multiply by 10 to get 80, and then take 3/8 of that to get 30. You should stop down to f/32, or perhaps 1/2 to 1 full stop further to compensate for unavoidable focusing and other errors.

This doesn't take diffraction into account, but diffraction is unlikely to be a serious problem for 5 x 7 photography.

[Once]

---
For evaluating the scene, you should put your eye at about the diagonal of the format from the ground glass. I don't have a 5 x 7 to measure, but I would guess that would be about 8 inches. ---
.

Sometimes I wonder if you're serious... An adult cannot see anything clearly at a distance of 8 inches! Even less at a distance of 6 in (in case of a 4x5 format). You would need to go back to your baby age of several months to see at this distance.
Your advice is complete and uttermost nonsense.

[Alan Curtis]

Last year I had cataract surgery on both eyes and gg focusing was a real problem. I went back to my ophthalmologist and told him I needed glass for a view camera he made me glasses that focused and magnified at 10-12". They work great and I now have both hands free to adjust and focus and no loupe required. Now I can see the entire gg magnified rather than the restricted area of a loupe.

[Vaughn]

Sometimes I wonder if you're serious... An adult cannot see anything clearly at a distance of 8 inches! Even less at a distance of 6 in (in case of a 4x5 format). You would need to go back to your baby age of several months to see at this distance.
Your advice is complete and uttermost nonsense.

You calling me a baby, mister?!

Just joking...FWIW, being very near-sighted, without my glasses I can focus at 3.75" (which is why I don't bother with a loupe.)

Vaughn

[Nathan Potter]

Once, not so for near sighted people. My wife can see my GG very clearly at 6 inches away without glasses. Several other LFers I know same deal and it has its convenience. Of course my wife is half blind at infinity without her glasses. Leonards case of an unaided one inch viewing distance from eye to GG is unusual - he must have been spectacularly nearsighted.

Nate Potter, Austin TX.

[Leonard Evens]

Sometimes I wonder if you're serious... An adult cannot see anything clearly at a distance of 8 inches! Even less at a distance of 6 in (in case of a 4x5 format). You would need to go back to your baby age of several months to see at this distance.
Your advice is complete and uttermost nonsense.

If you had read everything I said, you would have seen that I discussed that too. As it is, you completely misunderstood what I said.

Neither of us has any idea whether beemermark can see clearly at 8 inches. He certainly can't in his corrected eye. Whether or not he can in his `bad' nearsighted eye would depend on his degree of myopia. Before I had my cataracts removed, I was so myopic that without my glasses I could see clearly at about 1 inch. Having started getting nearsighted at age 10, I've been able to see things clearly very close up until at age 70. The plastic lenses inserted during the surgery corrected my distance vision to 20-20, so now I need glasses to see anything at all close-up.

My guess from what he said is that he can't see things clearly at 8 inches, but I have no way to be sure. He would probably need some aid such as a magnifier or reading glasses to do that.

The point of his so doing would be two-fold. First, and less important, 8 inches, being close to the diagonal of the format, is the proper distance from the point of view of perspective. Second, by getting somewhat closer, he would be able to focus better. Whether he would be able to focus well enough at 8 inches would depend on how he went about it. I think he probably wouldn't, so I suggested he get a loupe for focusing purposes.

[Leonard Evens]

Once, not so for near sighted people. My wife can see my GG very clearly at 6 inches away without glasses. Several other LFers I know same deal and it has its convenience. Of course my wife is half blind at infinity without her glasses. Leonards case of an unaided one inch viewing distance from eye to GG is unusual - he must have been spectacularly nearsighted.

Nate Potter, Austin TX.

About 8 diopters correction plus astigmatism. My daughter is even more nearsighted. But cataract surgery and the resulting implanted lenses can work miracles. Of course, I still have the underlying eye structure that led to the myopia, so I'm at risk for retinal detachments and other problems. I've also, of necessity, learned quite a lot about vision over the years.

[Once]

If you had read everything I said, you would have seen that I discussed that too. As it is, you completely misunderstood what I said.
---
First, and less important, 8 inches, being close to the diagonal of the format, is the proper distance from the point of view of perspective. ---.

Sorry Leonard, it's just one big nonsense. How could "the proper distance from the point of view of perspective" to evaluate the scene be a distance at which one cannot focus with normal good vision - that is beyond me. As I said - this advice is just plain nonsense because it cannot be practiced. Your illness aside (goodness, it's not a normal vision!) - the normal vision cannot follow your "rule" at all. And a 6x6 format - you would like to "correctly" see it licking the film, perhaps?

[Once]

Once, not so for near sighted people. My wife can see my GG very clearly at 6 inches away without glasses. Several other LFers I know same deal and it has its convenience. Of course my wife is half blind at infinity without her glasses. Leonards case of an unaided one inch viewing distance from eye to GG is unusual - he must have been spectacularly nearsighted.

Nate Potter, Austin TX.

Because your wife doesn't have the normal vision she cannot be a proof that a rule impossible to follow for people with a normal vision is a correct rule. The rule Leonard gives as advice is nonsense for people with a normal vision - therefore it cannot be a general rule.

[Nathan Potter]

Whew! Once! Many of my LF compatriots with normal 20/20 vision use plus diopter drugstore glasses to view the GG image at distances similar to what Leonard suggests. I use a plus 3 diopter at about 8 inches. This gives me a global view of the screen for the initial composition and initial standard adjustments. I then will remove the glasses and use a 5X loupe to ascertain critical focus in places where I need a critically sharp image.

I hadn't thought about the perspective deal mentioned by Leonard but it seems to make sense. If I'm using a 150 mm FL lens on 4X5 then I'll get a good sense of the scene by viewing the GG at 6 inches. Hmmm. maybe there's something to that. Although when using my 500 or 75 mm.I still view at 8 inches.

Nate Potter, Austin TX.

[aduncanson]

I hadn't thought about the perspective deal mentioned by Leonard but it seems to make sense. If I'm using a 150 mm FL lens on 4X5 then I'll get a good sense of the scene by viewing the GG at 6 inches. Hmmm. maybe there's something to that. Although when using my 500 or 75 mm.I still view at 8 inches.

I agree with what Leonard has been saying. However, in two respects it was not as clear as it might have been. The first is that we have to recognize that most adults do require magnifier glasses (drugstore readers) to achieve the close focus he recommends. The second clarification necessary has to do with the word "perspective". I would argue that when the subject is flat as in an image on a ground glass, perspective is entirely defined by the angle that one views from. That is, if I am directly behind the center of the image, the relationships between the objects making up the image do not change if I am 6 inches away or if I am 10 feet away.

To me, the "correct" viewing distance for the ground glass is approximately the negative diagonal because that is analogous to how I like to view prints. That is, I view prints from a distance about equal to the print diagonal. This allows me to evaluate the total composition while still seeing as much print detail as possible. Closer than that distance and I can no longer view the composition as a whole.

I do recall some author suggesting that all prints should be viewed from the taking focal length multiplied by the print magnification, but I was not convinced. That viewing distance may render the print's perspective as natural, but in doing so it robs the print of the power of the exaggerated perspective which is often the reason for choosing a near or a distant perspective on the subject. (No to mention the awkward interchange required to compel each gallery visitor to move to the single designated viewing position for each print.;) )

[Once]

---

I hadn't thought about the perspective deal mentioned by Leonard but it seems to make sense. If I'm using a 150 mm FL lens on 4X5 then I'll get a good sense of the scene by viewing the GG at 6 inches. Hmmm. maybe there's something to that. Although when using my 500 or 75 mm.I still view at 8 inches.

Nate Potter, Austin TX.

You see, even you contradict yourself.
Have you ever seen people reading a magazine? Do they lick the paper when looking at a small, 6x6 picture to have "the correct perspective" or to follow Leonard's rule of normality that, for people with normal vision, cannot be followed without special optical means? And when they look at a paper spread they ask the neighbor to hold the picture so that they can back away? That's the normality that Leonard sells to photographers. No wonder, he doesn't believe that a photographer can easily focus at something 600 y far away or more...

[Dave Jeffery]

Once,

I believe that all the near sighted / far sighted, proper perspective etc. etc. might have thrown you off a little. I read what Leonard wrote and interpreted it differently and hopefully I can rephrase things correctly as my method of focusing is the same as Leonard described, as quoted farther below. Leonard also wrote specifically for beermarks needs which I think is what may be confusing.

My vision is good at near 20/20. To initially evaluate a scene I keep my head back from the ground glass and try to place all the elements in the whole scene in a nice composition on the ground glass. I can do this without any magnification as I know by looking at the scene what the elements are when looking at the ground glass. All the parts of the scene are sharp on the ground glass but they still look far off. If I use reading glasses (3 X is what I use) the overall scene on the ground glass is brought in to closer focus which is very helpful. The desired scene can now be easily be composed looking at the whole ground glass.

Now that I have the scene composed and want to more closely focus on the far elements, and then the near elements, to set the best depth of field and focus spread, I use the loupe which is even more powerful.
This is probably a typical means of focusing for most people with normal vision.

I hope this rewording is helpful.

Leonard wrote
“For evaluating the scene, you should put your eye at about the diagonal of the format from the ground glass. I don't have a 5 x 7 to measure, but I would guess that would be about 8 inches. If you can get that close with your uncorrected eye, then use it for framing and generally evaluating the scene. If not, you would need some sort of magnifier or special glasses. (A loupe usually won't work for this because it has too narrow a view.) Viewing the scene with the proper perspective is often ignored, and I find it helps me enormously to do it.

For focusing, on the other hand, you should put your eye closer to the ground glass, and I would doubt that you can get it close enough on the basis of what you say. A loupe lets you in effect put your eye closer, so in principle you should use as powerful a loupe as you can find. But if the loupe is too powerful, you won't be able to distinguish surface features of the focusing screen from the image. The usual advice is not to go much higher than 4 X, and for many purposes 2 X will suffice.

[Once]

Dave,
your rephrasing is not what Leonard gives as advice and your method of focusing isn't either.
Leonard's "rule" to see the gg at a distance impossible for people with a normal vision to use without a special optical device is nonsensical. You too you don't look at the gg from that distance. What kind of glasses you use is completely irrelevant to the "rule" Leonard proclaims as -a "correct" one.

[Nathan Potter]

Dave, good synopsis of how many of us proceed thru image focusing.

Once, I'm not trying to argue about you're comments but I'd like, out of curiosity, to know what your focusing procedure is. Can you describe how you go about it.

Nate Potter, Austin TX.

[Leonard Evens]

Dave,

Thanks for restating what I said. You did a much better job of it than I did.

Let me add a couple of other comments.

If your eye is roughly at 6 inches when looking at a 4 x 5 ground glass image or at 8 inches when viewing a 5 x 7 image, what is recorded on your retina will be the essentially same as when you view an 8 x 10 print from 12 inches. That is just simple optics. But, I don't mean to claim that someone can't do good photography if his eye is not at the `correct' point.. The human visual system is good at correcting for such things. It is called size constancy; Smaller objects interpreted as being in the distance look larger .It works very well when looking at the actual scene, and it still works somewhat when looking at a print of the scene, even if there is a shift in point of view, provided it isn't too great.. After all, we can still make sense of a 4 x 5 contact print viewed from 12 inches, although we might have trouble with a 6 x 6 mm contact print and we certainly would have trouble with a 24 x 36 mm contact print if both were viewed from 12 inches.

So whether or not it is worth worrying about this is a personal matter. Many people are so used to evaluating the scene from 12 inches that they automatically make the necessary compensations. I find I do better by looking at 6 inches. As it happens, using the near point far point method to focus, that also provides enough magnification for me to focus accurately, so I seldom need to use a loupe.

Another related, but different, point came up. For what you see on the ground glass, or in a print, to correspond to what you see looking directly at the scene, again by simple optics, the focal length of the lens should also be the diagonal of the format. This fact explains the common `distortions' which result from using short focal length and long focal length lenses. For example, if a 4 x 5 picture is taken with a 75 mm lens and one views a resulting 8 x 10 print from about 12 inches, objects in the distance will look further away and smaller. In addition, a spherical object at the edge will appear to be stretched out into an ellipsoid. If you want to restore proper perspective you should view the 8 x 10 print from 6 inches. ( Of course an adult with normal vision won't be able to do that without a magnifier, but a myope without his glasses may be able to do it.) Then everything will look much more `normal'. Similarly, if the picture was taken with a 300 mm lens, distances will appear compressed. If you get back to 24 inches, things will look more normal.

It should be noted on the other hand that often this is a feature rather than a problem. When using a wide angle lens or long lens, we expect these things to happen and we use them aesthetically by causing the viewer to see the scene differently. So I am certainly NOT arguing that one should adjust the viewing distance to the print to match the focal length of the lens. Just that knowing about this will help you understand what happens.

[Once]

Dave, good synopsis of how many of us proceed thru image focusing.

Once, I'm not trying to argue about you're comments but I'd like, out of curiosity, to know what your focusing procedure is. Can you describe how you go about it.

Nate Potter, Austin TX.

Nate, the original discussion I was involved in was about the "evaluating the scene" as Leonard called it, on a gg, not image focusing.
The advice Leonard gives, to evaluate the scene, is to look at the gg in a way people with a normal vision cannot use. Just say to somebody with a normal vision to look at the gg of his roll film back 6x9 format from 4in of the distance and insist that it is the normal correct way of doing so, to "evaluate the scene"... If they look at you with a question mark in their eyes start to tell them that your sister/daughter/friend with a severe eye handicap can do so from just 3 inches... You got the point.

A totally different point, I did not discuss, is the focusing procedure. I use 8x Schneider Lupe - the same I inspect my slides with. Works well for me. My vision is normal, good, no eye glasses. Totally irrelevant to the discussed point of "evaluating the scene" on a gg. :)

[Once]

Dave,

---

Let me add a couple of other comments.

If your eye is roughly at 6 inches when looking at a 4 x 5 ground glass image or at 8 inches when viewing a 5 x 7 image, what is recorded on your retina will be the essentially same as when you view an 8 x 10 print from 12 inches.
---.

No, it's not, Leonard. A normal seeing adult person cannot focus at the gg from a 6in distance. What would be recorded on your retina would be a fuzzy, non sharp, painful image. Is it really so difficult for you to understand the basics of human vision? Or do you want to continue to force people's eyes to work in a way they cannot without special optical device?

[Leonard Evens]

No, it's not, Leonard. A normal seeing adult person cannot focus at the gg from a 6in distance. What would be recorded on your retina would be a fuzzy, non sharp, painful image. Is it really so difficult for you to understand the basics of human vision? Or do you want to continue to force people's eyes to work in a way they cannot without special optical device?

Look, this is getting annoying. You pull out of context quotes from what I said. I don't know if you do that because you can't read or because you intend to mislead. Please stop claiming I've said things that I didn't say.

Let me say it once again. Most adults with normal vision can't view the ground glass from closer than about 10-12 inches without aids. Due to personal experience, I've learned quite a lot about human vision, normal and abnormal. I believe I understand how it works pretty well. I've repeatedly said in what I posted that such people would need magnification provided by a simple magnifier or perhaps reading glasses of the right strength to view the ground glass closer than the normal near distance.. I also explained the reasons for choosing to view from such close distances, but I certainly don't believe everyone must do it, just because I said it. People can decide for themselves whether or not to try it.

Finally let me also say once again that the reason I brought this up in the first place is that the original post described someone who, from what he said, is clearly nearsighted in one eye, and I was trying to respond to him. He may very well be able to view a 5 x 7 screen from 8 inches without an aid. There is no way to tell how close he can get without knowing how much myopia and presbyopia he has.. But he will certainly be able to tell, and he can decide what to do.

I won't say any more on the subject, but I'm sure you will arrange to have the last word, whatever it may be.

[Once]

Look, this is getting annoying. You pull out of context quotes from what I said. I don't know if you do that because you can't read or because you intend to mislead. Please stop claiming I've said things that I didn't say.

Let me say it once again. Most adults with normal vision can't view the ground glass from closer than about 10-12 inches without aids. ----
----
I won't say any more on the subject, but I'm sure you will arrange to have the last word, whatever it may be.

Yes Leonard, believe me, it is equally annoying for me too (at least something we can agree about :) ). Nothing is put out of context.
Take it for a normal fact, that you cannot advice something as a normal procedure that should be done (evaluating the scene) when you need a magnifying hood (that's what you speak about, in fact) for that. That is a special procedure, not a requirement for a normal setup.
The fact that after being pushed like a mull you agree that people would need a magnifying device to follow your "normal" scene evaluation says that you finally got it. After all the stories of people with eye handicaps that don't need the device 'cause....
And yet we didn't speak about other nonsense that you spread with your posts - like not being possible to focus at something far away more that 1500 focal lengths etc. I just don't take whatever you come with.
The last word? I'm sure we will get yet another of your inventions soon...:rolleyes:

[Dave Jeffery]

Did I mention that using a 4X loupe on the ground glass that I can see a fly relieving itself out to 500 yards?