7
\$\begingroup\$

When shooting 2D objects (e.g., artwork), what is the easiest way to make sure that the optical axis of the camera is aligned perpendicular to the object? That is, how do I avoid any perspective distortion?

Of course I could just try to stare at the tiny viewfinder or the LCD screen and try to guess when it is aligned properly, but all too often you notice the tiny distortions only afterwards when you look at the photos on a large screen (for example, if the object is a perfect square and you crop it tightly, tiny distortions result in uneven margins around the object). Tethered shooting is one option, but what other tools or tricks one could use?

The best solution so far is the following: Replace the object with a mirror. Then (using liveview & zoom), align the camera so that I can see the reflection of the very centre of my lens precisely in the middle of the picture. Then put back the object and take the picture.

It works but it is not perfect; for one, it is not that easy to both align the camera perpendicular to the object and simultaneously keep the horizon level. The horizon is of course easy to fix in post, but it would not hurt to get it right directly.

Improve this question
\$\endgroup\$
3
  • \$\begingroup\$ You could try a tilt shift lens. \$\endgroup\$
    – dpollitt
    Commented Aug 11, 2011 at 18:01
  • \$\begingroup\$ Jukka - there is one keypoint missing in your question - what size of artwork are you talking about. Shooting a postcard size art can be easily done with a tripod facing down and the piece on the floor. However, a wall sized painting is much harder to shoot this way (this is what I have in my mind in my answer). \$\endgroup\$
    – ysap
    Commented Aug 12, 2011 at 17:14
  • \$\begingroup\$ @ysap: I would not like to restrict the question too much; I will be happy to hear any tricks and tips, even if some of them are only applicable in specific situations (such as small artwork). \$\endgroup\$
    – Jukka Suomela
    Commented Aug 12, 2011 at 22:13

7 Answers 7

Reset to default
3
\$\begingroup\$

Create a level surface to lay the artwork flat on - you can use a spirit level to make sure it is level.

If the artwork itself isn't very flat, either get a clean piece of glass larger than the artwork to lay on it or mount it to something flat. If using the glass approach you need to light the artwork with lamps to the left and right of the subject facing it at 45 degrees.

Then use a tripod with a built in spirit level (or get one of the hotshoe mounted levels) and level that looking directly down at the artwork.

This would more or less reproduce the environment I used to shoot artworks for greetings cards on back in my lab days except we had an industrial vertical camera mount with flat surface for the artwork attached below it, and I was using a bellows 5x4 plate camera :)

Improve this answer
\$\endgroup\$
2
\$\begingroup\$

A tripod with level is a possible solution, but if one is not available, then using a camera mounted level is a better solution.

In some cameras (Canon 7D for example) there is a built in electronic level that can be used as well.

UPDATE: following a couple of comments by @Itai and @MikeW in @Maynard Case's answer, lets put some things straight (pun intended):

  • You will never get perfect alignment consistently. "Perfect" here is relative, and I assume some error is allowed. This is not a NASA lab we are dealing with here. Also assuming the work itself is hanged pretty perfectly vertical.

  • You will always have geometry distortions. No matter what. The center of the artwork is closer to the camera than the midpoints of the edges, which themselves are closer than the corners, so even if everything is perfectly symmetrical, you will have some distortion. Heck, your lens will induce some barrel/pincushion distortion as well. The best thing that you can do is to minimize this effect by using as long a focal length as possible.

  • The mirror trick is completely unnecessary and redundant. If you are able to replace it with a mirror, then you certainly are able to just measure the center of the artwork (say, crosspoint of the two diagonals). Then, with a leveled camera (with whatever means already mentioned), use 100% live view to align the centerpoint to the center of the zoomed-in frame. The error margins will be at least as good as with the mirror trick.

UPDATE 2 (for OP's request): If one wants to align the camera in the left-right plane as well as up-down plane, then it is possible to use two strings of identical length attached to the artwork's corners. form a triangle where the it head is tied to the tripod's mount screw. Then, together with the center point that was found earlier and the camera being level, you have a left-right alignment as well.

You can also attach four strings and form a pyramid. Then, position the camera such that the center of your lens' front element is at the head of the pyramid. While the camera is pointing at the center of the artwork, you can't have better alignment than this!

Improve this answer
\$\endgroup\$
7
  • \$\begingroup\$ Ditto as with Maynard's answer. \$\endgroup\$
    – Itai
    Commented Aug 12, 2011 at 0:47
  • \$\begingroup\$ @ysap: I think you have misunderstood the mirror trick: It is not related to centering the artwork; centering is easy with live view, and fine-tuning is easy with cropping. However, even with the artwork centered and the camera perfectly level, the angle between the optical axis of the camera and the artwork might be, for example, 85° instead of 90°, and this is where the mirror trick certainly helps. (By the way, having the optical axis properly aligned not only prevents perspective distortions, but also makes sure that the focal plane is aligned with the artwork – no blurry corners.) \$\endgroup\$
    – Jukka Suomela
    Commented Aug 12, 2011 at 9:12
  • \$\begingroup\$ @Jukka - Sorry, but I think you have misunderstood my answer. If the artwork is hanged on a standard wall, then gravity makes sure that it is vertical (surely better than 5 degrees). Leveling the camera makes sure it is perpendicular to the artwork then. The mirror trick won't get you better than this. And surely hanging a mirror on or instead the artwork won't give you an exactly parallel surface too the artwork - not more than under the above assumptions. \$\endgroup\$
    – ysap
    Commented Aug 12, 2011 at 12:59
  • 1
    \$\begingroup\$ @Jukka - you are right, but this is easily solvable as well within the acceptable tolerances. Attach two same length strings to the corners of the artwork and form a triangle where its head is at the camera's position (the tripod's mounting screw for that matter). This will locate the camera exactly in front of the midpoint of the artwork that you found previously. \$\endgroup\$
    – ysap
    Commented Aug 12, 2011 at 14:20
  • 1
    \$\begingroup\$ @ysap: Now that is a good example of the kind of tricks that I am looking for! Perhaps you could post this as (another) answer? \$\endgroup\$
    – Jukka Suomela
    Commented Aug 12, 2011 at 14:36
0
\$\begingroup\$

Assuming the artwork is hanging on a vertical wall, you can use a tripod head which incorporate spirit levels on all three axes, and check the two axes are centered.

Improve this answer
\$\endgroup\$
5
  • 1
    \$\begingroup\$ This makes no sense at all. None of the level matter until the object is perpendicularly on the ground! \$\endgroup\$
    – Itai
    Commented Aug 12, 2011 at 0:46
  • \$\begingroup\$ @Itai - as is usually the case with artwork! Gravity makes sure it is as perfectly aligned as you can get, or at least as aligned as the wall's compliance with the construction code. Note the keypoint in Maynard's answer - "assuming the artwork is hanging on a vertical wall". I think the -1 is not justified here. \$\endgroup\$
    – ysap
    Commented Aug 12, 2011 at 0:58
  • 1
    \$\begingroup\$ Levels would make sure the camera is level, but doesn't assure it's at the right height, or the right position left and right. You still need some way (see the OP mirror trick) to make sure the camera is centered on the centre of the artwork. \$\endgroup\$
    – MikeW
    Commented Aug 12, 2011 at 4:48
  • 1
    \$\begingroup\$ Of course one possibility would be to place the artwork flat on the floor and then use 2 levels to make sure that the camera is pointing straight downwards. This has the same restriction as the mirror trick, though: the artwork might be rotated in the picture. That is, you get 2 axes of rotation right but 1 axis might be still wrong. \$\endgroup\$
    – Jukka Suomela
    Commented Aug 12, 2011 at 5:33
  • \$\begingroup\$ Another possibility would be to shoot artwork that is hanging on a wall, and combine the mirror trick (to make sure that the optical axis of the camera is perpendicular to the wall) and a spirit level (to make sure that the horizon is level). But this gets a bit fiddly and I was hoping that there might be a more straightforward approach. \$\endgroup\$
    – Jukka Suomela
    Commented Aug 12, 2011 at 5:37
0
\$\begingroup\$

I haven't tried it, but couldn't you use a laser measuring tool to measure the distance from each side of the lens to the artwork? They should be the same distance away. The tools are accurate up to +-2mm.

Improve this answer
\$\endgroup\$
0
\$\begingroup\$

  1. Place a mirror on the surface of the artwork.

  2. Point the camera at the mirror.

  3. Adjust the angle of the camera (and/or the artwork) until the the center of the reflected image of the camera lens is centered in the viewfinder.

  4. When the center of the lens image of the lens produced by the mirror appears in the center of the camera viewfinder, the mirror plane is perpendicular to the optical axis of the lens.

Or use a copy stand.

Improve this answer
\$\endgroup\$
0
\$\begingroup\$

Many cameras, especially mirrorless and good compact cameras, have a way to display an electronic level in the live view or electronic viewfinder. This question was asked when DSLRs were still the norm, but by now, this is likely the easiest way to achieve this.

A video of someone demonstrating this on a Sony a6300 can be found on YouTube.

If you use an Android phone, then you can use the "Open Camera" app, it has such a feature too.

Improve this answer
\$\endgroup\$
0
\$\begingroup\$

A refinement of the mirror system: Scribe or draw a fine line "X" on the surface of an ordinary mirror. Place mirror flat on artwork. Examine the image of the "X" mark in the viewfinder. If the camera is perfectly centered, you will see a clean "X". If not, you will see the "X" mark on the surface of the mirror does not perfectly align with its reflection in the mirror. An improvement of this technique is to mark the "X" on a small piece of flat glass and lay this on the mirror. This provides extra spacing between the "X" mark and the mirror silvering. This accentuates the double image should the camera be misaligned.

Improve this answer
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.