Classic & Vintage - Bicycle Picture/Image Error Question...

Bent forks! How many times have I seen those two word on the forum? However, I cannot help but wonder if the bent fork issue is, sometimes, a product of poor picture taking. I am speaking of the skewing of the image, that seems to be pretty common these days.

I might add that I suffer from the skewed image syndrome in my picture taking world also and I would like to correct that, if I could.

Here is a perfect example, of what I am talking about. Notice how the vertical lines(red) are, well, vertical, in the middle but then the fence slats begin to skew(yellow) out, at the top on both side of the picture. I think that, sometimes, this leads to skewing the angle of the fork, also.
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My questions are two. Why does this happen? And, how do we correct it?

Both wheels need to be equidistant from the fence.

Both wheels need to be equidistant from the fence.

Good point, but the issue is still the skewing. I should be able to take a picture of the fence, at any angle, without the skewing issue. Should I not? Also, why does it skew more at the top than it does at the bottom?

I have been experimenting and, I have noticed that using the zoom function, on my camera, will help to reduce the skewing. By standing far back, and zooming in, I can all but eliminate the skewing.

Randyjawa,
That is called barrel distortion. Very common, especially on most lenses commonly used on digital cameras, which tend to be on the wide angle side. It can be corrected two ways. Move farther away from your subject and crop the unwanted region out of the picture when you process, or, use a longer lens which will require a camera with inter-changable lenses. If your camera has a fixed zoom lens, try shooting pics in the longer zoom settings and stand farther away.
I've suspected too that many of the bent forks pointed out ...aren't.

Looks like you kind of answered your own question. High quality lenses are configured to correct for this common phenomena, among many others, but most digital cameras don't have high quality lenses. They're spendy!

I've suspected too that many of the bent forks pointed out ...aren't.

Yup, me too, however; vintage road bicycle frames are pretty fragile, when compared to most other bicycles genders.

Thanks for your input, rootboy. I suspected it had something to do with the lens but am anything but an expert on taking pictures. I would, however; like to improve my skill level so that I can better share my images with others and, perhaps, hear a bit less about bent forks.

Randyjawa,
That is called barrel distortion. Very common, especially on most lenses commonly used on digital cameras, which tend to be on the wide angle side. It can be corrected two ways. Move farther away from your subject and crop the unwanted region out of the picture when you process, or, use a longer lens which will require a camera with inter-changable lenses. If your camera has a fixed zoom lens, try shooting pics in the longer zoom settings and stand farther away.
I've suspected too that many of the bent forks pointed out ...aren't.

Let me just jump in here to concur with this assessment. The vast majority of "bent fork" and 'bent tube" photos I've seen illustrating the various threads on this forum are due, in large part, to barrel distortion. I suspect that many people are dealing with close quarters, which necessitates using the wide angle zoom range. As any portrait photographer will tell you, this will distort the image, which is particularly unflattering when applied to one's face! But the effect is amplified whenever you are photographing a subject with visibly apparent straight lines such as architecture ... or bicycle tubing. The lens effect doesn't go away - it is a net result of all lens design, in point of fact - however you can significantly downplay the distortion, as Rootboy points out above, by using a longer lens and by backing away from the subject being photographed. A particular flattering lens length is in the 85 to 105mm range. (This is what we refer to as "35mm equivalency" by the way; depending upon the size of your digital camera chip - and they do vary considerably, depending upon whether DSLR or point-and-shoot, etc. - your actual lens length will be much different. For instance, with one of my DSLR cameras, the effective focal length of the lens is multiplied by 1.5... i.e., a standard 50mm lens on a 35mm camera becomes and effective 75mm lens on a mid-range Nikon body. Sorry to open this can of worms, but the lens length isn't as clear as simply looking at the camera and reading the numbers.) Provided you have enough room to do so, a good rule of thumb is to try to place at least fifteen feet between camera and subject to minimize lens distortion, then zoom in tightly enough to fill the frame appropriately. If your camera has an option to display grid lines on the screen, try turning that feature on to compare the horizontal lines of the subject with the displayed horizontal lines and pay particular attention to what happens as those lines appear closer to the edge of the picture frame - this is where distortion will appear the most apparent, especially on the wide angle focal range. Sorry to be such a camera nerd - I teach this stuff for a living - but there does seem to be an appreciably comparable degree of attention to detail with my other nerdiness: bicycles.

If I have followed this discussion correctly, barrel distortion is a real distortion caused by the camera lens, in some cases more than others, which causes a photographic image to be distorted when the object photographed was not. Is that right?

But there is, of course, distortion that isn't in the image (or the object) but is inserted by the human brain. We call these things optical illusions, though they really result from unconscious mental processing-- one part of the brain interpreting the data before submitting it to the conscious part of the brain for further analysis.

For example, if confronted with two circles (or ellipses) that may or may not be the same size, and two lines that may or may not be parallel, the brain may chose the wrong one. Here are two circles of the same size:
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And here are two parallel lines:
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This particular example probably doesn't apply to bicycle photography very much, but it shows how the brain corrects for perceived problems that may or may not exist. I think this can cause us to see straight forks as bent, straight top tubes as bent, &c.

Simple:

- Plane formed by the wheels parallel to the film (or sensor) plane.
- Don't use a wide angle lens close up, use a longer lens farther away.

There's a reason portrait photographers use the 85-105mm lenses azorch mentions...they provide the truest representation of the subject with having to setup the camera 6 blocks away. Wide angle lenses will introduce perspective. In the pic randyjawa provided that is NOT barrel distortion, it is perspective distortion. This is the result of using a wide angle lens AND taking the pic from somewhat above the center of the subject. If this were barrel distortion the lines of the fence boards would be CURVED and equally at the top and bottom of the image. The lines clearly would converge at a point somewhere below the photographers feet.

This is barrel distrortion:

http://upload.wikimedia.org/wikipedia/commons/thumb/6/63/Barrel_distortion.svg/220px-Barrel_distortion.svg.png

This is pincushion distortion:

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Pincushion_distortion.svg/220px-Pincushion_distortion.svg.png

Perspective distortion with the photographer BELOW the center of the subject (lines converge at the top of the frame):

http://gimp.pixtuts.com/images/tutorials/perspective-destortion/perspective-distortion-grid.jpg

Perspective distortion with the photgrapher ABOVE the center of the subject (lines converge at the bottom of the frame):

http://www.pix-fix.com/fotofx/images/perspective3400.jpg

Barrel and pincushion distortion are caused by optics.

Perspective distortion is caused by too short a lens, too close to the subject. This is why many interior and architectural photographers use a tilt/shift lens:

http://www.usa.canon.com/CUSA/assets/app/images/Lenses_2009/TSE24/profile/tse_24mm_586x186.jpg

This lens actually "moves" so you can shift projection of the image circle to correct for perspective:

http://upload.wikimedia.org/wikipedia/en/f/fc/24mm-tilt-lens.jpg

Note how the lens is oriented to the film plane.

But, in short, with a normal lens use a longer focal length, keep the subject close to the center of the frame (meaning for a bicycle the camera is two feet off the ground), and BACK UP if you don't want perspective distortion introduced.

But, too far back with too long a lens then you start to introduce image compression, which is why portrait photogs don't use very long lenses...but that's a whole different can 'o worms.

Great thread for camera/bike nerds. I frequently use the aforementionned in-camera grid lines to check for distortion before shooting, and then back up to correct.

One other way to correct is to do it post-shooting in photoshop or other image processing software, most have a distoortionn correction feature. That's a whole 'nother subject though.

Rootboy and khatfull have it pegged. Follow their suggestions.

That said, I have sometimes (not always) added a bit of pinch in my photo editor - especially with side shots - until I can remove the bow put in the top tube by the lens' barrel distortion.

-Kurt

Just to beat this dead horse a little more, I'll add that my favored lens for flattering perspective is actually a 300mm (35mm equivalency)... in theory. In actual practice, one seldom has the necessary space to back up enough to use a 300, plus one needs a sturdy tripod to keep that huge chunk of glass steady enough to get a sharp, crisp, in-focus exposure. The only point in dredging up this extreme is to realize that the pendulum swings both ways: too wide/too close will generate unacceptable distortion for any type of structural/linear documentation, too long/too far will result in unacceptable hoops to jump through. Like the three bears, shooting to eliminate distortion means finding that "just right" place. Because most folks are using point-and-shoot cameras, the best advice is to zoom out enough to allow about fifteen feet or more distance between subject and camera. And Khatfull brings up an excellent point when it comes to rectilinear (perspective-based) distortion too - a level camera that is perpendicular to the subject will help to eliminate distortion of straight lines. To achieve this, take a ruler and measure the distance from ground to the top tube, locate the center point; then try to arrange your camera lens at that same approximate height: it's a whole lot lower than most photographs are taken (typically at eye-level, which is the most comfortable position for most "grab" shots.) It's easier with a tripod, but you can guesstimate the height hand-holding also. Be sure to be as close to a ninety degree angle as possible - i.e., equally far away from both the front and back tires, or your efforts will be for naught.

This is a terrific thread, by the way. There are some fantastic photos in this forum and I'm always very interested to hear what others have done to show off their rides in the most flattering way. I always cringe a little when photos pop up that are clearly shot from too close because the inevitable comment immediately follows.

Forks bent.

Bent forks! How many times have I seen those two word on the forum? However, I cannot help but wonder if the bent fork issue is, sometimes, a product of poor picture taking. I am speaking of the skewing of the image, that seems to be pretty common these days.

I might add that I suffer from the skewed image syndrome in my picture taking world also and I would like to correct that, if I could.

Here is a perfect example, of what I am talking about. Notice how the vertical lines(red) are, well, vertical, in the middle but then the fence slats begin to skew(yellow) out, at the top on both side of the picture. I think that, sometimes, this leads to skewing the angle of the fork, also.
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My questions are two. Why does this happen? And, how do we correct it?

There are two issues at work, the first has been eluded to, cheap cameras with cheap lenses, especially at short focal lengths will have barrel distortion, which requires extra lens elements to correct, it is not uncommon for a DSLR standard lens to have as many as 18 separate elements, and some of those are there to correct this. Cheap cameras with zoom lenses may have as few as 2 or 3 elements. With barrel distortion, straight lines will look like this () in the image posted, this is not the case.

If you take a photograph of a tall building, you will often, get an image where the sides of the building appear narrower at the top, this is because the camera plane is not parallel with the building plane, and because the bottom is closer to the camera then the top, it appears as if the top narrows. In a bicycle picture, many people stand in front of the bicycle, and then tilt the camera down, again the camera plane is not parallel with the bicycle plane, and the bottom will appear narrower then the top. It's only straight lines that will show this, downtubes, seat tubes and forks are straight lines, so it appears that the angle is wrong, and that the fork is bent. The way to avoid this distortion, is to lower the camera, if your photographing a bicycle that is 36" tall, the camera should be held 18" off the ground so that the planes are equal, if the bicycle is in front of a fence then you want the fence, the bicycle and the camera plane all parallel to get a good photograph. This may mean attaching the bike to the fence. Bike photos, they should be in front of a plain white surface, professional photographers will use special paper or cloth mounted on a frame for this. if the bicycle is leaning, then you want your camera even with the top tube so that the angle of bicycle and camera plane are equal. This applies to all directions, a bicycle where the rear wheel is further out then the front wheel, will have the same issue in the other direction.

And Khatfull brings up an excellent point when it comes to rectilinear (perspective-based) distortion too - a level camera that is perpendicular to the subject will help to eliminate distortion of straight lines.

Damnit, recilinear...that was the word I was looking for. Dang you people who really know photography :)

That said I think that probably is the source of many of the "bent fork" pics we see: short lens, camera above subject, perspective converges at the photogs feet, the front wheel looks closer to the downtube than it should, POOF!, bent fork.

The real way to try to judge a bent fork from a pic, and still not perfect, would be to take the pic into your favorite photo editor and draw a line through the center of the head tube down through the fork. See where the rake ends up. While there still could be perspective distortion there a truly bent fork should make itself clear if you do that.

There are two issues at work, the first has been eluded to, cheap cameras with cheap lenses, especially at short focal lengths will have barrel distortion, which requires extra lens elements to correct, it is not uncommon for a DSLR standard lens to have as many as 18 separate elements, and some of those are there to correct this. Cheap cameras with zoom lenses may have as few as 2 or 3 elements. With barrel distortion, straight lines will look like this () in the image posted, this is not the case.

If you take a photograph of a tall building, you will often, get an image where the sides of the building appear narrower at the top, this is because the camera plane is not parallel with the building plane, and because the bottom is closer to the camera then the top, it appears as if the top narrows. In a bicycle picture, many people stand in front of the bicycle, and then tilt the camera down, again the camera plane is not parallel with the bicycle plane, and the bottom will appear narrower then the top. It's only straight lines that will show this, downtubes, seat tubes and forks are straight lines, so it appears that the angle is wrong, and that the fork is bent. The way to avoid this distortion, is to lower the camera, if your photographing a bicycle that is 36" tall, the camera should be held 18" off the ground so that the planes are equal, if the bicycle is in front of a fence then you want the fence, the bicycle and the camera plane all parallel to get a good photograph. This may mean attaching the bike to the fence. Bike photos, they should be in front of a plain white surface, professional photographers will use special paper or cloth mounted on a frame for this. if the bicycle is leaning, then you want your camera even with the top tube so that the angle of bicycle and camera plane are equal. This applies to all directions, a bicycle where the rear wheel is further out then the front wheel, will have the same issue in the other direction.

See my discussion above about perspective...illustrations even. :)

Provided you have enough room to do so, a good rule of thumb is to try to place at least fifteen feet between camera and subject to minimize lens distortion, then zoom in tightly enough to fill the frame appropriately. If your camera has an option to display grid lines on the screen, try turning that feature on to compare the horizontal lines of the subject with the displayed horizontal lines and pay particular attention to what happens as those lines appear closer to the edge of the picture frame - this is where distortion will appear the most apparent, especially on the wide angle focal range.

This part I understand and thanks for bringing it down to a layman's level. I thought about the step back thing and have been having better results. However, I was not trying to fill the available space, opting to crop later. As soon as you mentioned that, I immediately saw the opportunity to improve.

And thanks for all of the other advice, even though my poorly trained self could grasp little of it. Gotta try some shots of the Cinelli frame set again, today...

This part I understand and thanks for bringing it down to a layman's level. I thought about the step back thing and have been having better results. However, I was not trying to fill the available space, opting to crop later. As soon as you mentioned that, I immediately saw the opportunity to improve.

And thanks for all of the other advice, even though my poorly trained self could grasp little of it. Gotta try some shots of the Cinelli frame set again, today...

Randy, easy enough...if your camera has a zoom lens set it around the middle of it's zoom range and then "frame with your feet". Duck down a little to get the top tube closer to the center of the frame. There ya go.

If your camera doesn't have a zoom lens then it likely has a 35mm focal length equivalent lens, which means it's pretty short, and it will be difficult for you NOT to introduce some kind of perspective and yet frame the bike fully in the viewfinder. In that case you should move back, then expect to crop later. That will have the same effect as the above.

Great posts on optics and tips for photos.

Hopefully the fence was installed plumb and level. You could also put a torpedo level on the top tube to check for level on the bike.

You could also use a bubble level accessory for the hot shoe on the camera if you're using a typical DSLR:
http://www.bhphotovideo.com/c/product/263729-REG/Manfrotto_337_337_2_Axis_Flash_Hot.html

Or put your point-and-shoot digital on a tripod and then check it's level with the torpedo level on top. Some DSLRs, like the Nikon D700 pictured, have a virtual horizon feature that displays on the rear TFT screen to help with leveling.

My preference would be to use a short telephoto lens designed for macro/micro photography; most of these are designed to have low distortion levels:
http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/224-micro-nikkor-af-s-105mm-f28g-if-ed-vr-review--test-report?start=1

As an aside, that cheesy Promaster filter on a $1700 Nikkor TS lens is funny.

As an aside, that cheesy Promaster filter on a $1700 Nikkor TS lens is funny.

Hahaha, I hadn't noticed that...all my Canon L glass has Hoya SuperHMC. I can't see spending for B+W. :)

I had a Tamron 90mm macro....and SO regret selling it. It was good for danged near everything. Slow focus though (typical of macro lenses).

"My preference would be to use a short telephoto lens designed for macro/micro photography; most of these are designed to have low distortion levels"

...Yes, Leftthread. That's one reason I now use a vintage Nikon 55 mm macro lens on my Canon crop body DSLR. SHARP too.

And Randyjawa. If the shots of the Cinelli don't work out ...try a couple of shots of tequila. I find it helps me forget about my bent fork.

Well, I took some shots of the Cinelli, just to test what I have learned. Though not quite perfect, the results are greatly improved.
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Well, I took some shots of the Cinelli, just to test what I have learned. Though not quite perfect, the results are greatly improved.
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Your choice of vertically striped background also helped out, I think! Glad all of this esoteric camera stuff helped out. It's a lot like "velo-speak," in the way that photography tends to get a little bit arcane at times.

looking better. However, unless I'm wrong, looks like the camera focused on the fence and not on the frame. Is it just me? But ...that's a whole other can of worms.

However, unless I'm wrong, looks like the camera focused on the fence and not on the frame.

Focus on the Cinelli? Good idea. I did not know that I could focus the camera. I press the little button half way down. The image comes into focus. And I go click. Or, perhaps, snap would be a more appropriate choice of words.

At any rate, I am happy that I asked the simple question.

So far, my picture taking improvement program includes: stand back, zoom in, fill the screen, focus and snap. How'm I doin?

Randy, if your camera does not have manual focus, you may be able to press halfway down, to lock exposure and focus, then step back the 8 inches or so from the background to the frame to have it in focus.

Also, is that a repaint & replacement fork on the Cinelli? I thought all of them has chrome lugs on the frame, and no lugs on the fork.

Also, is that a repaint & replacement fork on the Cinelli? I thought all of them has chrome lugs on the frame, and no lugs on the fork.

Yes, the frame has been painted, professionally, and bears the painter's sticker.
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The forks are not Cinelli. I did not get the original forks with the bicycle. I did, however, miss out on an Ebay set last week because I am am stupid, from time to time.

When I first got the bike, it was with the intention of just selling it and I still lean in that direction (too many bikes in my stable and I am serious about culling the herd - sold two nice ones last week). But now, as I look at the bike, I think, not bad. Got it mostly fitted with Nouvo Record stuff, at the moment, but only loosely bolted into place. I am playing with my resolve.

A 4x5 view camera will correct perspective/distortion, to the point that it will make a bent fork look straight.
http://www.vancouverphotoworkshops.com/workshops/images/largeformat2.jpg

A 4x5 view camera will correct perspective/distortion, to the point that it will make a bent fork look straight.
http://www.vancouverphotoworkshops.com/workshops/images/largeformat2.jpg

Oh, no question about it, provided you have a 4x5 with tilts and shifts (as opposed to an old Graflex, for instance). But taking advantage of perspective correction using a 4x5 is well beyond the skills (and convenience!) of nearly everyone except the pros and seriously accomplished amateurs who use them regularly. Except in some specialized areas, most pros have even abandoned their view cameras in favor of digital capture. I sold my last view camera and lenses perhaps three years ago and my 8x10 enlarger left the studio at least six or seven years ago. Which brings us back to the intention of the original posting: how does the average C&V enthusiast manage to create good quality images of their bicycles with acceptable/minimal degree of distortion and probably using a consumer-available digital camera. The suggestions in the thread thus far have been excellent. There's a good thread (http://www.bikeforums.net/showthread.php/702525-taking-bike-pictures) in the C&V forum where a member has posted details of how he/she goes about setting up shots in the garage. The thread illustrates the lighting setup (standard two-point soft lights, set up on 45 degree angles with the subject positioned on a "seamless" backdrop.) For those interested in a good "starting point" for photographing their bikes, here are a couple of links I've bookmarked on my computer that I think are worth looking over:

http://raydobbins.com/photosetup.htm
http://bhovey.com/Masi/MasiPhoto/Photo.htm