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Thread: Technique for focusing "into your scene"

  1. #21

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    Re: Technique for focusing "into your scene"

    Quote Originally Posted by AdamD View Post
    I guess forget all that noise....why "median of (A,B)" and not 1/3 towards the minimum extension or 1/3 of (A,B)?
    You’re assuming the relationship between standard extension and focusing distance is linear, which it is not.
    Just do the test : pick points A and B, mark the position of the standard and then put the standard on the median point. Are you now focusing exactly in the middle between A and B?


    EDIT : actually you don’t even need a view camera to test this. If you have a lens with a focussing scale hanging around you can check the markings :

    Click image for larger version. 

Name:	74B2DC8C-58E4-46A6-95FE-9EF73038C441.jpg 
Views:	21 
Size:	48.1 KB 
ID:	214325

    Here you can see that extension wise, 2m is halfway between 1.5m and 3m, when in your scene 2m is roughly 1/3rd of the way between 1.5 and 3m.
    "I am a reflection photographing other reflections within a reflection. To photograph reality is to photograph nothing." Duane Michals

  2. #22
    Alan Klein's Avatar
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    Re: Technique for focusing "into your scene"

    Quote Originally Posted by lenicolas View Post
    You’re assuming the relationship between standard extension and focusing distance is linear, which it is not.
    Just do the test : pick points A and B, mark the position of the standard and then put the standard on the median point. Are you now focusing exactly in the middle between A and B?


    EDIT : actually you don’t even need a view camera to test this. If you have a lens with a focussing scale hanging around you can check the markings :

    Click image for larger version. 

Name:	74B2DC8C-58E4-46A6-95FE-9EF73038C441.jpg 
Views:	21 
Size:	48.1 KB 
ID:	214325

    Here you can see that extension wise, 2m is halfway between 1.5m and 3m, when in your scene 2m is roughly 1/3rd of the way between 1.5 and 3m.
    That's correct. The halfway is really the same relationship of 1/3 to 2/3 (approx I believe) on 4x5's and my bellows operated Mamiya RB67. Movement gets less the further the focal point is from the camera. If you were to mark the hash marks on the 4x5 camera bed with distance in feet or meters, you'd see the same nonlinear distances as in your picture of the lens marking of distances. Of course, you'd have to mark it separately for each of your lenses.

  3. #23

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    Re: Technique for focusing "into your scene"

    Quote Originally Posted by AdamD View Post
    Doremus, this is all very well said. But this is what I'm trying to understand better.

    How about this....here's a link to 4 shots I just took the other day. You can download them and zoon in further than SmugMug will allow. Anyway, you will see soft spots in these images even though all of these areas fell within my near and far focus points on the rail. It would have been my expectation that everything should have been pretty much the same sharpness, but not so....I'm trying to understand why.

    Of course one possibility is that I THOUGHT all the areas were within the near and far focus points of travel, and maybe I was wrong. But I'm thinking by moving the standard to the mid-point of the near and far points on the standard rail markings that I caused the problem and I should have set the standard closer to the max extension point.

    Anyway....take a look at let me know if anyone can detect any potential causes.

    https://fountainphoto.smugmug.com/Fi...umb-3-27-2021/

    Image 1: 150mm Rodenstock f/5.6. 1/15 sec @ f/25 orange filter
    Image 2: 150mm Rodenstock f/5.6. 1/15 sec @ f/20 orange filter
    Image 3: 90mm Rodenstock f/6.8. 1/15 sec @ f/20 orange filter
    Image 4: 90mm Rodenstock f/6.8. 1/8 sec @ f/22 orange filter

    Arca-Swiss F-Line Classic with the MicroOrbix. Focus in the highest farthest point, MicroOrbix tilt for the nearest lowest. Image 4 was the easiest to get this clean.

    Any thoughts??
    Adam,

    Some thoughts :

    First, just because you choose near and far focus points and then set the focus halfway between them doesn't mean that you have enough depth of field for the extremes; that depends upon the aperture. The farther apart the focus points are (call it the focus spread distance) the smaller aperture you'll need to get everything acceptably sharp. That's all in the article that I linked to in my first post.

    Second, as Corran mentioned above, there's really only one sharp plane of focus; everything else is out of focus proportionally to how far it is from the plane of sharp focus and the aperture you've chosen. The object is to have the out-of-focus blurs (blurry circles/circles of confusion) to be so small in the final print that our eyes can't tell the difference between them and the really sharp points. You can see, then, that whether something ends up appearing out of focus also depends on the degree on enlargement. Make a contact print and it looks really sharp; enlarge it 10x and everything starts to look soft...

    So, the idea is to find the optimum aperture for the focus spread you have and the degree of enlargement you are planning on making (or, conversely, knowing how large a print you can make from a particular negative before it appears soft in areas you want sharp). Again, the article I linked to goes into this. Really, it's worth doing your homework here to save yourself a lot of headaches later.

    Lets talk about movements a bit while I'm at it: Movements are used for two reasons: image control (e.g., correcting converging parallels) and optimally positioning the plane of sharp focus in the scene. The latter is the important one here and is achieved with tilts and swings (note that rise/fall doesn't reposition the plane of sharp focus; just takes a different slice of the image circle).

    When positioning the plane of sharp focus with a view to getting everything in the scene as sharp as possible (which I think is what you're trying to do), the object is to get it as close as possible to the near and far focus points. The problem is, when you move the plane of sharp focus around, the points that are nearest and farthest change around too. If you, say, tilt the front forward a bit, which results in tilting the plane of sharp focus down in the scene a bit more in that same direction, the points you choose to focus on are no longer the ones nearest to and farthest from your camera position. Let's say you tilt so that the top of a near rock and a far mountaintop are in the plane of sharp focus. Now, the farthest point from the plane of sharp focus might be a spot at the base of the mountain, and there may be no point nearer than the top of that near rock you focused on. Note also, that the mountaintop is just as close to the plane of sharp focus as the top of the near rock. (This scenario is a common mistake made by people just learning camera movements.)

    You can see, in the above example, that the plane of sharp focus isn't at an optimal position between near and far points; it's intersecting the nearest point and some distance from the farthest point (which is at a point that seems counter-intuitive at first...). The solution is to choose better reference points; focus halfway down into that near rock and halfway down the mountainside so the tops of the near rock and the mountain are "closer" and the bottom of the near rock and the base of the mountain are "farther" from the plane of sharp focus.

    Now, you've positioned your plane of sharp focus well, but you still need to focus the camera (many think they are done at this point, but no!). Find the closest point, i.e. which point in the scene needs the most bellows extension to be sharp on the ground glass. Note this position; it's your "near" focus point. Now do the same for the far; search around in the scene and find the point that requires the least bellows draw. This is your far focus point.

    Once you have those, note the distance between the two points, set your focus halfway between them on the rail/camera bed and, importantly, choose the optimum aperture for your focus spread so that everything stays acceptably sharp.

    If you've done your homework, you've got a sticker or a table that you can easily reference to tell you what aperture to use for what focus spread.

    Alternately, you can set your focus and stop down, observing your focus points through your loupe until they become acceptably sharp and use that aperture. Many do this. The problems with the visual method, however, are that the ground glass can get too dark to view in many situations (low light, etc.), the grain of the ground glass can keep you from being able to tell when things are right, and you're not really balancing diffraction degradation with depth of field (unless you're using a really powerful loupe and a really fine ground glass, anyway). Still, many say, "stop down till everything is sharp enough, then stop down one more stop," and do fine. I like my focus-spread tables.

    Finally, let's look at one of your photos as an example. I don't know what you find unsharp about it; I can't see things on the website very well, but I can till you how I'd go about setting up for it. The photo is the second one, the one with the hillside and rock outcropping that slope up to the left.

    I'd want to place my plane of sharp focus diagonally in this scene, laying it down a bit with tilt and then tipping it sideways a bit with swing so that the near right corner of the plane of sharp focus was the lowest and the far left was the highest (hope that makes sense). I'd pick two points on the vertical center axis for my tilt reference points, say halfway up that cholla in the foreground and halfway up the rock outcropping. I'd apply the tilt first. Then, I'd choose two reference points for the swing on the horizontal axis, say halfway up the slope on the left and the middle of the bright rock on the right. I'd then apply the tilt.

    After that, I'd search around the scene, focusing on different things to find which are actually the "near" and "far" focus points, all the time keeping in mind where my plane of sharp focus lies. So, I'd check the tops of the rock outcropping and the tops of the near bushes/cacti for near points. Ideally, they should all be in focus at roughly the same position (if there are large discrepancies, I might rethink my movements). I'd find the one with the greatest bellows draw and call that "near" and note the position on the camera (my cameras all have scales on them). Then, I'd look around for the "far" (this time, something below the position of the plane of sharp focus), likely the hollow at the base of the outcropping or the ground near the camera. After finding the one that needs the least bellows draw, I'd note that position and then proceed as described above; finding focus spread and choosing aperture.

    Sorry this got so long; I didn't have time to write a shorter response

    Doremus

  4. #24

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    Re: Technique for focusing "into your scene"

    Quote Originally Posted by reddesert View Post
    Other people have explained that the 1/3 rule of thumb isn't really accurate. It also predates digital BTW. But anyway, the simple explanation for the difference in these rules of thumb is that the 1/3 rule applies to the distance in the subject space, like your subject is from 10 to 40 feet away so you focus at 20 feet. The rule you quote for 4x5 of focusing at the mid-point is in the image space, where you're splitting the positions of the standard corresponding to near and far in half.

    Because the relation between image distance from the lens and subject distance from the lens is not linear, these rules of thumb are less different then you might imagine. The difference is not that 35mm/digital has a different DOF from 4x5. Rather, it's mechanical: in 35mm/digital you're usually looking at the focusing distance scale of a lens that gives subject distance, while with an LF camera you can more easily measure the position of the image (the standard).

    reddesert,

    This exactly explains my question and is a great answer. THANK YOU!! This makes total sense. Very helpful.
    Anything in life worth having is worth sharing.

  5. #25

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    Re: Technique for focusing "into your scene"

    Quote Originally Posted by Doremus Scudder View Post
    Adam,

    Some thoughts :

    First, just because you choose near and far focus points and then set the focus halfway between them doesn't mean that you have enough depth of field for the extremes; that depends upon the aperture. The farther apart the focus points are (call it the focus spread distance) the smaller aperture you'll need to get everything acceptably sharp. That's all in the article that I linked to in my first post.

    Second, as Corran mentioned above, there's really only one sharp plane of focus; everything else is out of focus proportionally to how far it is from the plane of sharp focus and the aperture you've chosen. The object is to have the out-of-focus blurs (blurry circles/circles of confusion) to be so small in the final print that our eyes can't tell the difference between them and the really sharp points. You can see, then, that whether something ends up appearing out of focus also depends on the degree on enlargement. Make a contact print and it looks really sharp; enlarge it 10x and everything starts to look soft...

    So, the idea is to find the optimum aperture for the focus spread you have and the degree of enlargement you are planning on making (or, conversely, knowing how large a print you can make from a particular negative before it appears soft in areas you want sharp). Again, the article I linked to goes into this. Really, it's worth doing your homework here to save yourself a lot of headaches later.

    Lets talk about movements a bit while I'm at it: Movements are used for two reasons: image control (e.g., correcting converging parallels) and optimally positioning the plane of sharp focus in the scene. The latter is the important one here and is achieved with tilts and swings (note that rise/fall doesn't reposition the plane of sharp focus; just takes a different slice of the image circle).

    When positioning the plane of sharp focus with a view to getting everything in the scene as sharp as possible (which I think is what you're trying to do), the object is to get it as close as possible to the near and far focus points. The problem is, when you move the plane of sharp focus around, the points that are nearest and farthest change around too. If you, say, tilt the front forward a bit, which results in tilting the plane of sharp focus down in the scene a bit more in that same direction, the points you choose to focus on are no longer the ones nearest to and farthest from your camera position. Let's say you tilt so that the top of a near rock and a far mountaintop are in the plane of sharp focus. Now, the farthest point from the plane of sharp focus might be a spot at the base of the mountain, and there may be no point nearer than the top of that near rock you focused on. Note also, that the mountaintop is just as close to the plane of sharp focus as the top of the near rock. (This scenario is a common mistake made by people just learning camera movements.)

    You can see, in the above example, that the plane of sharp focus isn't at an optimal position between near and far points; it's intersecting the nearest point and some distance from the farthest point (which is at a point that seems counter-intuitive at first...). The solution is to choose better reference points; focus halfway down into that near rock and halfway down the mountainside so the tops of the near rock and the mountain are "closer" and the bottom of the near rock and the base of the mountain are "farther" from the plane of sharp focus.

    Now, you've positioned your plane of sharp focus well, but you still need to focus the camera (many think they are done at this point, but no!). Find the closest point, i.e. which point in the scene needs the most bellows extension to be sharp on the ground glass. Note this position; it's your "near" focus point. Now do the same for the far; search around in the scene and find the point that requires the least bellows draw. This is your far focus point.

    Once you have those, note the distance between the two points, set your focus halfway between them on the rail/camera bed and, importantly, choose the optimum aperture for your focus spread so that everything stays acceptably sharp.

    If you've done your homework, you've got a sticker or a table that you can easily reference to tell you what aperture to use for what focus spread.

    Alternately, you can set your focus and stop down, observing your focus points through your loupe until they become acceptably sharp and use that aperture. Many do this. The problems with the visual method, however, are that the ground glass can get too dark to view in many situations (low light, etc.), the grain of the ground glass can keep you from being able to tell when things are right, and you're not really balancing diffraction degradation with depth of field (unless you're using a really powerful loupe and a really fine ground glass, anyway). Still, many say, "stop down till everything is sharp enough, then stop down one more stop," and do fine. I like my focus-spread tables.

    Finally, let's look at one of your photos as an example. I don't know what you find unsharp about it; I can't see things on the website very well, but I can till you how I'd go about setting up for it. The photo is the second one, the one with the hillside and rock outcropping that slope up to the left.

    I'd want to place my plane of sharp focus diagonally in this scene, laying it down a bit with tilt and then tipping it sideways a bit with swing so that the near right corner of the plane of sharp focus was the lowest and the far left was the highest (hope that makes sense). I'd pick two points on the vertical center axis for my tilt reference points, say halfway up that cholla in the foreground and halfway up the rock outcropping. I'd apply the tilt first. Then, I'd choose two reference points for the swing on the horizontal axis, say halfway up the slope on the left and the middle of the bright rock on the right. I'd then apply the tilt.

    After that, I'd search around the scene, focusing on different things to find which are actually the "near" and "far" focus points, all the time keeping in mind where my plane of sharp focus lies. So, I'd check the tops of the rock outcropping and the tops of the near bushes/cacti for near points. Ideally, they should all be in focus at roughly the same position (if there are large discrepancies, I might rethink my movements). I'd find the one with the greatest bellows draw and call that "near" and note the position on the camera (my cameras all have scales on them). Then, I'd look around for the "far" (this time, something below the position of the plane of sharp focus), likely the hollow at the base of the outcropping or the ground near the camera. After finding the one that needs the least bellows draw, I'd note that position and then proceed as described above; finding focus spread and choosing aperture.

    Sorry this got so long; I didn't have time to write a shorter response

    Doremus

    Doremus,

    You totally outdid yourself. I love this post. So thoughtful and I totally followed you. I can see why you are suggesting swing, but that didn’t even occur to me in the moment.

    Thank you so much. This is a post I will be saving to reread over a few more times.

    Adam
    Anything in life worth having is worth sharing.

  6. #26

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    Re: Technique for focusing "into your scene"

    You and me Adam. DS is always good reading.
    Principal Unix System Engineer, Yoyodyne Propulsion Systems

  7. #27
    Alan Klein's Avatar
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    Re: Technique for focusing "into your scene"

    And cameras with asymmetrical tilt on the rear standard, I focus far let's say half up the mountain lining up the far line on the ground glass and then tilting the rear back for the close element, stopping down to f22. How could I make that better?

  8. #28

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    Re: Technique for focusing "into your scene"

    Here is an example I've lifted directly from my recent post in the LF Images section. First, the image...followed by process notes:

    Click image for larger version. 

Name:	Lighthouse Quarters, Pemaquid.jpg 
Views:	30 
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    There are three major object plane angles in my image...the foreground fence which goes to the left, the building wall - congruent to the first mentioned plane but at a different distance, and the fence section starting at the right and ending at the building. The lawn is yet another plane, which I consider to be less important here. The roof is yet another...which does not worry me at all as it is dark, plus not so challenging as the lawn.

    I took this photo a number of years ago...but looking at it now, I can imagine that I'd first want to swing the front (or rear) to establish focus of both the extreme right fence post and the extreme left of the building in this image - then swing back from this, so that now the fourth post from the right (of the fence running to the building) would be in focus, and pull back a bit so the extreme right of the building is now just a bit fuzzy. Then, I'd want to tilt the lens down...just a bit, to attempt to accommodate the roof plane, which would bring this plane forward to bisect the front-left fence at about 1/4 up from the bottom of the frame.

    Then I'd stop down quite a bit. Likely to right between f/32 and f/45. A bit risky with such a short(ish) FL - I'm also almost certain that I went right to a red filter for this image...which would help restore some of the apparent sharpness which may have otherwise been lost to diffraction.

    Do keep in mind that the two aspects in my favor are...One - I'm using a 90mm lens, so visible DOF will tend to fall off a bit less than it would with a longer FL. And two - the right side of the building and the right side of the fence are in pretty deep shadow...which gives me an opportunity to be more "neglectful" of those areas, focus-wise - making my task a bit easier. If you look closely at these shadow areas, they are indeed just a bit fuzzier than the brighter parts.

    At any rate...lots of little compromises here and there - but I do think I pulled it off (just barely!).

  9. #29
    Drew Bedo's Avatar
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    Re: Technique for focusing "into your scene"

    Many years ago a workshop leader said something like . . ."The ground glass it truth." Meaning is i is not seen on th gg it will not be in the negative.

    Along with doing much of the five steps in the OP one of the things I also do is to actually put a focusing target or several of them into the composition. assy to do with a table top still life, it can also often be done out doors. With a easily seen high contrast set of bar codes (or a black and white checked shirt) in the field of view , all the tilting and focusing in and stopping down can be done wit a higher degree of confidence.

    Just be sure to tske these focvusing sids out of the composition before tripping the dhutter.
    Drew Bedo
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  10. #30
    Tin Can's Avatar
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    Re: Technique for focusing "into your scene"

    Good tips, I also use, including tiny flashlights for corners

    In our Post-Reality Photo Art era, I am going to include my markers occasionally

    as they are Truth

    Quote Originally Posted by Drew Bedo View Post
    Many years ago a workshop leader said something like . . ."The ground glass it truth." Meaning is i is not seen on th gg it will not be in the negative.

    Along with doing much of the five steps in the OP one of the things I also do is to actually put a focusing target or several of them into the composition. assy to do with a table top still life, it can also often be done out doors. With a easily seen high contrast set of bar codes (or a black and white checked shirt) in the field of view , all the tilting and focusing in and stopping down can be done wit a higher degree of confidence.

    Just be sure to tske these focvusing sids out of the composition before tripping the dhutter.
    2022

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