How to take photos of a knot! - ways to achieve a clear background

[xarax]

get the camera as close to the knot as possible and still get a focus.

   If you get the camera as close as possible, and you set the aperture wide open, as you say, you do not have a sufficient depth of field (you have a shallow focus), so, if the knot is bulky, parts of it stay out of focus...I prefer to use the tele range of a super zoom lens, that distort the object much less than a wide angle lens, but to get a focus I have to climb on a ladder, and go up and down many times, to be sure that the free ends of the knot are placed right ...and you can not place a tripod on a ladder, so it is difficult to place the center of the knot on the center of the picture s frame ! Pain in the back ! 

  Finally, suspend the knot a fair distance from the background

   Easier said than done...And how do you suspend the two or four free ends, so they go to the right direction into the picture frame as you want them to go ? (Stay aligned, for example, or parallel...) You should have many years of experience with marionettes, to be successful in this!   

[[Inkanyezi] gone]

I think the crucial part in any photo is lighting.

When we want a neutral background, any colour might do, even one that does not contrast from the main subject, provided there is contrast in just any way between the subject and the background.

The image I attached is a colour photo of two almost monochrome ropes against a likewise almost monochrome backdrop. The difference in structure between the ropes clearly outlines which parts belong to which rope. The background coincides in colour with the ropes. The f-stop is small, in order to have sufficient depth of field over the subject, but at such a small distance with a tele lens, the depth of field does not include the background.

The knot is suspended from one of my light stands. It hangs vertically, the braided rope topmost, and the camera is held in portrait position. Lighting is backlight from a large window above and to the right of the background, which is the inside of my balcony door. A white screen at the left side reflects some light, to alleviate contrast and to brighten the left side (bottom in the image as posted). A shaving mirror throws some light onto part of the knot structure to enhance detail.

I think it is possible to trace the entire knot in spite of lack of colour contrast and with little contrast against the background. It should be possible to do the same also with brightly coloured and patterned rope without much risk of confusion, just putting attention to clarity in the image. It is a matter of using the light to make the image, and trying to make any important part visible, although it needs not stand out brightly.

Good sharpness is a boon, but not entirely necessary, the crucial part is the way light falls upon the subject.

[alpineer]

I think the crucial part in any photo is lighting.

A most excellent demonstration Inkanyezi. Good to here from you.

alpineer

[xarax]

   Inkanyezi, you are a f...good photographer ! ( So, you are NOT permitted to do mistakes when you shoot knots.... )
   Now, you suspend the knot in mid air, so it is easier to use the shallow focus effect...But, doing this, you have no control on the orientation of the free (not tensioned) ends, which follow their own directions. I want the orientation of the free ends to be somehow controlled , so I have to lay the knots on a horizontal plane.   ( Or, I have to attach invisible lines to the free ends, and exercise in marionettes handling...)  Also, you can not suspend a loose knot ( that serves as a tying diagram) : many, even all, of the parts of the knot should be suspended in such a case, so you have to be an expert on marionettes as well !   If you let the knot on the ground, and use a tele, as I do, you have to climb on a f...ladder,, to get your subject into focus, and go up and down the ladder to make corrections. And you can not put a tripood up there, on the ladder ! Also, there, it is more difficult to focus on the knot, and have all its parts sharply focused, into the shallow depth of field. My pictures suffer from this problem...

[xarax]

If you shoot against a white background, it is easy on the toner/ink - in that, the printer will only print the knot structure and not the gray-scale background too.

Oouts ! THAT is a major blow to my black background attitude, indeed !

   An easy way to recover, somehow, from this blow, is to invert the colours of the pictures, so, a black or dark background turns into a white or a soft white background.
   Now, there is a trap here...Black shadows turn into iluminated areas, so the pictures get a Gothic style appearence... More shadows in the original picture means more Gothic-like illuminated areas in the final, transformed picture. So, If one uses this technique, it is better to have as few dark shadows as he can.
   With this simple one click trick, one can transform my old black-background pictures posted on this Forum to white background ones, so he can print them without paying a fortune in black ink...Of course, the result has no relation to agent smith s high quality photos, but the job can be done...and the orange rope turns into a blue one, without any additional expenses ! 

   See the attached picture for such inverted-colours pictures of knots. I used the free program GIMP 2.6, and the function "Inversion", from the menu "Colours".

[[Inkanyezi] gone]

If a semi-rigid material is introduced into the center of the cord, as a soft iron wire or a copper wire, it can be bent to just about any shape and stay that way while taking a photo. Depending on how much time you dedicate to it, you may make it very convincingly floating in mid-air, and the end can be pointed any direction you fancy. It may even be bent in such a way that the rope surfaces will not touch in the crossings.

[xarax]

Depending on how much time you dedicate to it, you may make it very convincingly floating in mid-air

   It is very difficult to make the soft wire penetrate a long segment of α rope lengthwise...I know it because I had tried it for another reason: It had occurred to me that, if I could do this, and take a CT of the knot, ( I have a friend working as α radiologist at a hospital ), I would have a very accurate description of the path of the rope in 3D. After this, it would not be difficult to convert the pixel image of the curve onto a vector image, and then proceed to re-draw the knot with a computer graphics software program. That way we can have a virtual reality image of the knot, and be able to rotate it, and view it from any angle...I was nor successful to make the wire pass through the axis of the rope, if the segment was not very short. Maybe you can try it and succeed.  

[alpineer]

An easy way to recover, somehow, from this blow, is to invert the colours of the pictures, so, a black or dark background turns into a white or a soft white background.

That's an interesting solution xarax. I guess we'll have to provide a new classification for these inverted knots.

alpineer

[[Inkanyezi] gone]

It's like everything in this world; maybe extremely difficult the first time you try it, but once you've got the hang of it, it is rather easy. For inserting a metal wire, it helps if the tip of it is round; the easiest way to accomplish it is to double it like a hairpin in the end. If you then wish to remove it, you continue in the same direction, taking it out at a convenient point. It is easiest with double braid rope. In laid rope, the wire can be laid into the centre.

To take this picture, I suspended the knot from the back of a chair and took it against a cupboard door in my kitchen, backlighted from the window and with the shaving mirror illuminating it from the front. Both these pictures are taken with a compact camera, Canon PowerShot G7. Any camera that can be set to compensate for a light background can do this. I used compensation +2 and white balanced for the cupboard door.

Then of course we have the Indian rope trick if all else fails... (The quena is my main instrument http://www.youtube.com/watch?v=R2qdbiierJI )

[xarax]

 
http://igkt.net/sm/index.php?topic=3258.msg19536#msg19536

[[Inkanyezi] gone]

I think that a major consideration when taking a picture of a knot is to make the knot itself as legible as possible. For simple knots like the bowline, it might suffice with one face of the knot to get the three-dimensional idea of its topology, provided the image shows the flow of the line into the knot, which is related to the flow of force in use. In a bowlinesque knot as the Eskimo Bowline, an image as the one in http://igkt.net/sm/index.php?topic=3233.45 is a bit confusing to interpret, as it hides the nature of the TurNip, even if the image is perfectly clear. The more common flattened form of the TurNip in my opinion is a better presentation, as it to me is a more true image of one of the states while tying the knot.

So the problem that has to be coped with when photographing a knot is twofold: How will the knot be best represented, in order to easily be correctly interpreted, and how should it be shot so that the image as clearly as possible shows its topology?

[xarax]

In a bowlinesque knot as the Eskimo Bowline, an image as the one in http://igkt.net/sm/index.php?topic=3233.45 is a bit confusing to interpret, as it hides the nature of the TurNip, even if the image is perfectly clear.

Yes, but how beautiful is this perfectly clear image ! See the almost sexy shape of the shadow of the nipping loop on the eye leg of the bight and the tail !

   I always show a "front" and a "beck" ( or a "top" and a "bottom") view of any knot, except when those views are identical. Sometimes, I show a side view as well, with the knot diagonally placed into the frame of the picture. It might well be a carefully chosen angle for a knot, from where everything is unambiguous, but it s a hard thing to search for it in each and every knot. I can not do this for all the knots I tie and post pictures of, pictures that I consider to be just a helpful, easy to make documentation of the knots I happen to meet. But I would love to see a good photographer, like you, to take some sophisticated pictures of some of those knots. When I will get rid of most of them, by the strength test during the "knot wars" I plan , then I will take out my film 6X6 heavy gun, the high resolution scanner, and all the sophisticated lighting appliances of a studio, to compete with you guys !   The pictures I have posted could well have been replaced by sketches, but I wanted to present the knots in an easy way that anyone in the Forum could also do, with a minimum of time spend !  With the technique of the digital camera without any other flash than its own, the large diameter / two colours ropes, the positioning of them on the floor, I wanted to establish a tradition that everybody could follow, ( so we reduce all this annoying endless blah blah and misunderstandings about things that could be clarified in a second ). So, I want a simple, easy to follow technique that does not make people reluctant to follow it, because they might fear they are not able to achieve good results with it.  A technique that is as a simple as writing, and run a lesser danger to drive us to misunderstanding and "knot-tiers wars"( as the silly one we fought a few months ago...  )  
   I am afraid that your proposed wire skeleton ropes, that allows us to suspend any rope tangle, tightened or not, in mid air and use light, mirrors and a shallow focus to have a clear background, however ingenious, is too complex and difficult for the average person in this Forum. Of course, I would love to see your pictures taken that way ( and presented one by one at different posts, so you can use the maximum allowed KB limit for each of them ) !

[xarax]

   Another easy way to have a white background, is to shoot the pictures on a blue or green one first, and then remove the colour, using one of the many commercially available software programs. This technique is nowadays cheap, quick and effective. It enables us to place the (tightened or even loose) knot on the floor (so we do not have to suspend the knot s nub and the free ends in mid-air), and use the camera s flash, because, with the dark background, we avoid any annoying reflections.
   I have used the free, demo version of FXhome PhotoKey 4, available at :
   http://fxhome.com/photokey-4
   For more information about this technique, see
   http://en.wikipedia.org/wiki/Chroma_key
  One has just to insert a picture by the command "import" on the foreground frame menu, and then choose the command "export", and save the transformed picture on his computer. As simple as that, a matter of a few seconds ! The blue or green dark background disappears, and in its place we have a very soft white/grey tone.   See the attached pictures, for the application of this simple, easy and quick technique on images of a knot that was placed on a blue towel on the floor.

[xarax]

Just use a white background, people.

I am afraid things are not so simple, Korgan...
We can not USE a white background when we shoot the pictures, because of the flash reflections on it. We want to HAVE a white background in the final product, for printer s sake..., but shoot the pictures on a dark background, that absorbs reflections.

use a solid colour, then replace that colour using almost any given graphics software.  I use Irfanview.

  No. Infanview changes the RGB combination configuration to any other R, G, B combination, it changes the order of the sequence of the three (R, G,  B) primary colours. It does not turn the RGB configuration into a RGW one ! ( W= white) Also, we do not want to turn the colour of the background into a white, everywhere in the picture ! We want to erase only the solid dark colour that is confined into the background area, not this colour everywhere of the frame. You need a  Chroma key program to do this, like the one I have mentioned. If you discover a free Chroma key program, please send it to me...  
   And what happens when we already have pictures with a black background ? If we turn black into white, we lose all the shadows, and replace them with Gothic-style strange illuminations...No, believe me, you can not do a summation of those two pages in a single line !  

[knot4u]

Agent_smith, I just realized you're the one posting the pics with the white backgrounds.
http://igkt.net/sm/index.php?topic=3233.0
Those pics are about the best I've seen.  If you include some of those pics in your original post, you'd be an instant authority.  A picture says a thousand words.  New people have to do a search.

Xarax's pics are good too, but he often shows the knots tightened up.  It's often like a mini puzzle to figure out the knot.