Saturday, 3 August 2013

Distorted images

With the development of photographic equipment over the last decades, we have been able to capture more accurate representations of the reality than ever before, and at a higher resolution and lower cost. Some are obsessed with the sharpness of lenses, and closely read MTF tests to find the best. And there is a trend now that sensors have a weaker anti-aliasing (AA) filter, or even gets rid of it completely, to reveal even more details.

Still, there are some who go in the opposite direction, and use the camera not to accurately depict the reality, but to deliberately distort the reality in various ways. One example is the "Instagram" trend, in which filters are often applied to images to distort the colours, add dark corners, add film grain noise, and so on.

In this article, I look at some methods for creating images that are not natural looking.



Pinhole photography


Using a pinhole is like turning the clock back some 150 years. Pinhole photography has been around for hundreds of years, although initially used for projecting images in a camera obscura for watching or drawing copies of.

The easiest way to try out pinhole photography with a Micro Four Thirds camera is to buy a pinhole lens. The term "lens" here is of course wrong, since there are no glass elements, just a very small hole let the light through. I have tested the Wanderlust Pinwide (my review here), which is a sensible pinhole. Unlike most others, the hole itself is recessed into the lens mount, to give a wide angle effect.

The pinhole corresponds to an aperture opening of approximately f/96. So to be able to take this photo at 1/40s, I set the ISO to 6400 on the Panasonic GH3:



There are several things to note about the picture. First of all, the sharpness is quite poor. This is related to the size of the pinhole. The pinhole cannot capture any details smaller than the hole itself, compared with the sensor size. Hence, on the Panasonic GH3, you will not get details smaller than around 30 pixels in diameter.

Still, the pinhole could not have been made much smaller. A smaller hole means less light gets in, and pushing the ISO even higher makes it hard to use. So I think Wanderlust have struck a sensible balance here between sharpness and light gathering capability.

Another thing to note is the vignetting. The picture is significantly darker outside the centre area. There are two reasons for this. One is the lack of lenses, which means that the light cannot be distributed evenly to the corners. Rather, the relatively longer distance from the pinhole to the sensor corner, compared with the sensor centre, contributes to the vignetting.

The other factor is the angle of the light hitting the sensor. Outside of the centre, the angle becomes steeper, and the sensor does not handle this well. Especially the green channel appears to be sensitive to the angle, which explains the purple tint.

Another interesting aspect of pinholes is that there is no focus mechanism. Everything is equally much (or less) in focus. This can be used to combine near and far objects in the same picture, like in this example (ISO 3200, 1/20s):



Using ISO 3200 or 6400, is is even possible to record videos using the Wanderlust Pinwide. Here are some examples:



Rather than buying a complete pinhole, you can also make your own. A common way to do so is to get a spare camera body cap, drill a hole in the centre of it. Next, cover the hole with tin foil, and punch a very small hole in the foil with a needle. It is important that the hole is as round as possible. A DIY pinhole made this way would have a focal length of around 20mm, the register distance of the Micro Four Thirds format. With the longer focal length, you will probably get less vignetting than in the example above.

IR images


Using an IR filter blocks the visible light, and hence, allows you to photograph light outside of the visible spectrum.

A number of different types of IR filters are available. Usually, they are categorized by the cut-off frequency. Visible light roughly goes from 340nm to 740nm, with ultra violet (UV) to the left of the visible spectrum, and infrared (IR) to the right, see the illustration below.


The idea of the IR filter is to remove light which is to the left of the cut-off frequency, only leaving the infrared parts of the spectrum. This can work more or less well, depending on the camera sensor, and the filters in front of the sensor. Usually, the camera already has filters built in to block off the infrared light, since it can potentially degrade the image quality of the visible spectrum.

So when using an IR filter, you usually get many stops less light, and must use a tripod or increase the ISO a lot to be able to photograph. You may also have problems focusing using the autofocus.

To see the effect of an IR filter, here are some images taken with and without it. Without filter, GH2 with Lumix 20mm f/1.7, ISO 160, f/5, 1/160s:


With IR680 filter, GH2 with Lumix 20mm f/1.7, ISO 160, f/2, 1/2.5s:


Based on the exposure settings, we see that the IR680 filter steals about eight stops of exposure, which is a lot. Normally, you need to use a tripod and a slow shutter speed when using an IR filter.

So how is this interesting? It is just a very red tinted photography. However, when opening the RAW image, one can adjust the white balance, which gives a result like this, leaving some false colours:


The cut-off frequency was probably a bit too low here. At 680nm and above, there is still some visible red light coming through. So I think that a filter with a cut-off frequency of 720nm is better.

The camera's sensitivity to IR light varies, as I said. My experience is that the Panasonic GH3 blocks out most infrared light, and is not well suited for this. Based on what I have read, though, the Olympus OM-D E-M5 is quite sensitive to IR light, and would be a better choice for this use.

If you are serious about IR photography, though, you would not use a stock camera. Rather, you would get a camera IR converted, meaning that the filter in front of the sensor which blocks out IR is replaced with a filter that does not block IR, or is removed altogether. This conversion service can be found online by searching for "camera IR conversion". Typically, it involves sending your camera to a technician, who will do the conversion for you at some cost.

You could also try to do the conversion yourself, however, you risk permanently damaging the camera. Search for "DIY IR conversion" for some conversion guides.

Tilt lens/tilt adapter


Tilt/Shift lenses usually very expensive, specialized lenses used for perspective control, or changing the focus plane. A typical application is architecture photography, to achieve square corners despite having the camera tilted upwards.

Another use of tilting the lens, is to achieve a cute miniature effect. Essentially, you can tilt the lens upwards or downwards, to change the focus plane so that only a horizontal line across the centre of the frame is in focus. This makes it look like the depth of focus (DoF) is small, and hence, the viewer's brain is fooled into believing that the photographed subject is very small. Here is an example video using this effect:



To achieve this, I used a Lensbaby Tilt Transformer with an old Nikon 50mm f/1.8 AIS lens attached. I tilted the lens downwards, and set the aperture f/5.6. Then, I turned the focus ring until the centre of the frame was in focus:



To control the amount of blur outside the centre, you can use both the tilt and the aperture. A large aperture (small f-number) exaggerates the effect, as does a large tilt angle.

You can use any lens for this application, as long as it can be mounted to the adapter (Nikon mount). Preferably, the lens should have a manual focus ring and aperture ring, for easy setting of the image parameters.

If you don't have a Nikon mount lens, you can still use the Lensbaby Composer in a kit with the Tilt Transformer. Using a similar kit, I took the following picture: (My review here.)



There is also a specialized tilt/shift lens for Micro Four Thirds, the Photex 50mm f/2 Tilt Shift lens. I have not tested it, but it appears to be useful, with a maximum tilt of +/- 8°, and a maximum shift of 11mm. The lens can be rotated 360°, so that the shift can be applied in any direction.

On the negative side, though, the focal length of 50mm is quite long, and the lens would be difficult to use for architecture. You would need to get very far away from a building to be able to photograph it with a focal length of 50mm, often impossible due to narrow streets.

Fisheye lens


There are two native fisheye lenses for Micro Four Thirds, Samyang/Rokinon 7.5mm f/3.5 and Lumix G 8mm f/3.5. Out of the two, the Samyang/Rokinon is my favourite, due to the low price, great optical performance, and less geometric distortion, compared with the Lumix G 8mm lens.

Fisheye lenses distort the projection of the image. So the colours, sharpness, and so on, are just as usual. Only the projection is distorted, compared with how we perceive the reality. This can be used for many interesting and fun effects. In the image below, I have pointed the camera upwards inside a circular back yard:



The fisheye lenses also have an impressively short minimum focus distance. Also, setting a small aperture gives you a very deep depth of focus. Combining this enables you to capture images where both small and large items are visible at the same time. Here is an example (f/16, 1/100s, ISO 1600):



Sadly, there are no circular fisheye lenses available for the Micro Four Thirds format. Yasuhara are making the Madoka 180 7.3mm f/4 circular fisheye for Sony NEX (my review). They claim to have a Micro Four Thirds version coming, but I doubt it: The lens has a too large image circle for the Four Thirds sensor.

Using the Yasuhara Madoka 180, I took this picture in Times Square, by directing the camera upwards:



Using the lens to make videos can be fun:



Rolling shutter


The Panasonic GH3 has an electronic shutter option, with which you can take pictures silently. This feature is also found on the G5 and G6. However, there is a significant side effect: The image is exposed sequentially over a period of 1/10s, which can product severe rolling shutter effects, if you move the camera, or if the subject moves, during this time.

On the other hand, what is normally a negative side effect, can be used creatively. Here, I have photographed a bass player with the Panasonic GH3 in electronic shutter mode. The image parameters were 175mm, f/5.6, 1/800s, ISO 200 (Lumix X 45-175mm lens):



Taking a picture like this would have been impossible without the rolling shutter artefacts of the electronic shutter mode. So this is an example where you can use the side effects creatively.

Mirror reflex tele


The Tokina 300mm f/6.3 (my review) is an example of a mirror reflex tele lens, a popular lens type some decades back. For a tele lens, it is very compact, due to the mirror construction. On the other hand, it suffers from poor contrast with back-lit subjects, and has donut shaped out of focus highlights (bokeh).

The donut shaped bokeh is of course a distortion of the reality, and can be very distracting. Here is an example image showing the effect:



However, you could choose to view the donut bokeh as a charming effect, rather than a nuisance. Here are some example images where I have used the donut shaped bokeh as an effect. Both images were taken at night time, with some street lights in the background producing the donut highlights:

Focus distance around 2 meters, ISO 800, 1/3s, f/6.3:



Focus distance around 7 meters, ISO 1600, 1/2s, f/6.3:



This effect can also be used to create an abstract video:



Compressed perspective with a tele lens


A tele lens can be used to compress the perspective, compared with how we normally perceive the reality. This effect can be used in urban environments to create images where a deep distance into the picture looks more shallow.

Here is an example image, taken at the constitution day parade in Oslo, using the Lumix G 100-300mm f/4-5.6 at 300mm, 1/200s, f/6.3, ISO 160:



Sadly, a side effect of using a tele lens at a long distance is that you commonly get atmospheric distortions, which ruin the sharpness. Here is a crop from the picture to illustrate this problem:



The issue with atmospheric distortions cannot be fixed by setting a faster shutter speed.

Another example of a compressed perspective from a busy market street, using the Lumix X 45-175mm f/4-5.6 at 175mm, 1/400s, f/6.3, ISO 1600:



The street is 200m long, but looks shorter, due to the compressed perspective.

Panning


Using a slow shutter speed while following the subject with the camera as you press the shutter is a common way to make the images more lively.

Here is an example where I used a Yashica T5 compact point and shoot camera loaded with Fujifilm Velvia slide film. The film is rated at ISO 50, which is quite low. The low ISO, in combination with the late evening light, made the camera employ a slow shutter speed. As the car drove by, I followed its motions with the camera as I took the picture:



With a digital camera, it is much easier to take these kinds of pictures, since you can see the results straight away, and find the shutter speed you think works the best. A good starting point is to set a shutter speed of 1/10s.

Macro photography


Photographing very small objects is called macro photography. This is not a distortion of the reality as such, but you could create images which you would not normally be able to see with your own eyes. By using a very cheap reverser ring, I was able to mount the Lumix G 14-42mm lens reversed, for a very large magnification effect.

An example image taken this way, at 14mm f/14:



Note the dots throughout the image. They are probably dust particles on the sensor, and come into focus when using extremely small apertures, like in this case. Otherwise, they don't cause any negative effects. This is an example where macro can be used to make ordinary items look extraordinary.

My favourite way to achieve macro with a normal lens now, is to use macro extension rings.

Other examples


A friend of mine uses a Panasonic GF1 camera at ISO 1600 when photographing in daylight, simply because he deliberately wants the noisy images. I'm sure some of you are laughing at this, but it is an example of the same thing: Using the photographic equipment to distort the image, to achieve some specific effect.

And I think this is one of the reasons why photography is such a great hobby: It enables you to manipulate the images in an infinite number of ways, giving a huge creative potential.

Can you think of other examples of using photography to distort the reality?

5 comments:

  1. Hi!

    Nice post, similar to the kind of things I've been playing with, often inspired by some of your posts. M4/3 is nice in that sense: you can easily mount legacy lenses, and there are many cheap adapters and lenses. I'm tempted by the mirror lens now ,-)

    Maybe one thing that is missing in your list is long exposures with ND filters (ND400 or something), fun to "remove" people from pictures (if they move enough), or smooth down water (sea or river).

    And rolling shutter artifacts (but you blogged about it before ,-)).

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    1. Yes, you are right! Long exposures is a way to distort the image, and create a different view.

      Also, rolling shutter is a good comment. I like that.

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  2. Some more things to distort/detail out reality as captured by photography:
    * Spherical Panoramic Images and presenting the world around ther shot as small planet; requires some technical steps, though:
    https://www.mopswerk.de/panorama-tutorial/
    * the new cams capturing the light field cams that allow you to choose point of focus in post processing
    * focus stacking methods
    * Bokehrama shots (Panoramas taken with photos at shallow depth of field to get pictures with an ultra shallow depth of field)
    Cheers, Henrik

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    Replies
    1. Thanks for your comments. Regarding bokeh, I really agree with that. This may be a bit controversial, but I think that pictures with a very selective focus have been a big trend in popular photography the last 10 years or so. And this is clearly an effect which "distorts" the pictures, compared with how the reality looks.

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  3. Here's just another way of showing "what was not there but got captured":
    http://fqwimages.com/time-dimension/

    ReplyDelete