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Wednesday, February 10, 2010

Digital Troubleshooting Sensors & CCDs

If you're having an issue with your (straight out of the camera) digital images, it may be one of the following things:
Dust on your sensor... If you see little specks on your images, probably in the same areas, it's most likely dust. This is very common, and pretty easy to fix. There's a few options to clean your sensor including: by the cameras "sensor clean" in the menu, by store bought kits, or by a professional repair shop. This will only occur on a digital SLR, happens often, and is mostly preventable. For tips to keep this mess out of your life, refer HERE and HERE.
This is an example image from a bad CCD. This can happen in both point & shoot digital cameras and digital SLRs. This is especially a common issue in many of the older p&s. This is an extreme case of bad CCD, but they sometimes go out gradually and you may have your actual taken image with some minor lines or discoloration through it. This is not an easy problem to fix, and is not an issue for home repair. If you have this problem, you will need to send that camera out to a repair shop, or in some cases may be under warranty through the distributor.
Thursday, February 18, 2010

G9 Franiec Lens Ring

If you happen to purchase one of the Franiec lens rings for the Canon G9, (shown here- it's all back vs. the Canon's stock ring which has a silver stripe around it), be aware that there's a slight trick to getting them on properly.
The ring must be mounted with the small bayonet flange facing up. Be gentle, and let it click into place. If it's forced on, the only way to remove it is to cut it off. This seems to be a common problem, as we've seen many of these that have been forced on.
Thursday, March 04, 2010

Digital Pinhole Follow Up

After reading the post on digital pinhole posted a few weeks back, one of our technicians here at KEH Camera thought that in addition to diffraction itself being the factor in the softness of the digital pinhole images, that there was much more to it. He decided to delve into deeper research to support his theories. For the technical people out there, this post is for you. Kris has shared his findings and sources as to why this happens.

In addition to light diffraction, a couple of other factors contribute to digital pinhole images being fuzzy and out of focus ( for essentially, they are out of focus.) These factors are focal plane & depth of focus.

Pinhole photography differs from traditional photography in that it is lensless. The photography concepts that we are taught, and so familiar with in traditional photography are completely absent and do not apply to pinhole photography. Namely, focusing mechanism and focal plane.
As you may know, we need a focusing mechanism and a flat plane (along with a proper shutter speed and a stable platform for supporting the camera) to obtain a sharp image. A pinhole camera has no focusing mechanism and, since it is lens-less, depth of field does not exist.

The focal plane in a film camera is different from that of a digital SLR sensor. Film is one flat plane once it is properly loaded inside a camera. A digital SLR's sensor, although it appears flat, is made up of several different layers of light gathering and protective materials. The nature of a pinhole's poor image resolution is also amplified by the sensor's micro-mirrors and photo-sites.

A simulation of a Circle of Confusion resting on/at a film plane, by Kris Phimsoutham
A simulation of a Circle of Confusion resting on/at a sensor, by Kris Phimsoutham
 The CCD and/or CMOS sensors have several layers of protective and light-gathering materials built on top of the actual material that does the capturing of an image. When a circle of confusion reaches the camera's sensor, the focal plane is resting several layers above the image capturing layer. Since it is a pinhole-fitted camera, the circle of confusion cannot be focused to fall on the plane of the image capturing layer. The sensor is simply capturing what it sees resting on the top layers, which captures and appears as fuzzy and unsharp.

To further explain these concepts, the following section is being used with permission by the author of www.cambridgeincolour.com.

Circle of Confusion

"Another implication of the circle of confusion is the concept of depth of focus (also called the "focus spread"). It differs from depth of field in that it describes the distance over which light is focused at the camera's sensor, as opposed to how much of the subject is in focus. This is important because it sets tolerances on how flat/level the camera's film or digital sensor have to be in order to capture proper focus in all regions of the image."

Depth of Focus & Aperture Visualization

"The above diagram depicts depth of focus versus camera aperture. The purple lines represent the extreme angles at which light could potentially enter the aperture. The purple shaded in portion represents all other possible angles. The diagram can also be used to illustrate depth of field, but in that case it's the lens elements that move instead of the sensor.

The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus -- and increasingly so depending on how far apart the light rays are."

Digital SLR sensors were invented to capture images through optical lenses. Until sensors can be made to act like film, conventional pinhole photography, as it is, isn't viable without post-capture processing. This doesn't mean it is impossible to create beautiful, artistic and expressive images from your digital pinhole camera. Artists such as Sam Wang, Nancy Spencer, Eric Renner and numerous others have been exploring and defining digital pinhole imagery with great success and profound impact.

~Kris Phimsoutham + Noted Sources
Tuesday, March 16, 2010

Troubleshooting Light Leaks

There are a few different issues that can cause light leaks. If you're unfamiliar with what a light leak is, it is basically a space on the camera that allows light to "leak" into the inside and therefor over exposing the film. It will sometimes cause a white or red area on the film/print that shouldn't be there. If the leak is bad enough, it can fog your entire image.

One of the main causes of light leaks is bad light seals. In most 35mm and medium format camera, the seals are made up of a foam padding. The foam deteriorates over time. Foam is typically found around the entire back door of the camera, above the mirror, and around the focusing screen and prism (in cameras with detachable prism housings). In some cases, the foam may have been replaced by a rope type seal, which holds up better over time.

To check and make sure your foam is still good, it's simply a matter of stickiness and/or brittleness. First, check to see if the foam padding is still there. Then answer these questions: Is there little black specks falling out from the inside of the camera? Does the foam look moldy? Is there a sticky black substance around the edge of the door? If you answered yes to any of those, then your foam is bad. Having the foam replaced is a fairly inexpensive job, and can be done at most camera repair shops.
The red lines indicate where light can seep in through. Around the perimeter of the camera back, there should be a solid strip of foam. The shutter blades in the middle may also cause exposure issues if they are broken.
Foam padding at the hinge of the back door to a 35mm. This foam is bad, as it has some mold on the surface, is flaking away, one strip is missing, and is starting to stick.
Foam pad in lens mount above mirror

In medium format backs, there is also a type of light seal that may cause fogging of your film. These seals are not easily seen and not as easily fixed. Other things that can cause light leaks include casting cracks in the camera body, and holes in large format bellows. Casting cracks are thin cracks in the body of a camera. These happen most often around screws that have been tightened too much, if there is impact damage, and near delicate, small parts. Bellow holes can be seen if taken into a completely dark room with a flash light. Insert a flash light gently into the bellows and go slowly along all edges. If you see even the tiniest spot of light, it will effect your image. Neither casting cracks or bellow holes are easy to fix and usually must be fully replaced. In some cases, the bellows may be patched.

The only case in which a light leak is usually wanted, is when shooting with a Holga.

It's a good idea to check these things on a fairly regular basis, and super important to check if you've had the equipment sitting around for while, especially if it's been stored in a garage or attic. The temperatures and weather conditions cause the equipment components to break down must faster than if it were properly stored.
Thursday, March 25, 2010

Sensor Check

Sometimes you may see obvious spots on your images that are a dead giveaway that you have a dirty sensor. But, if you tend to shoot with a wider aperture, you may not have noticed it so much. Here's a quick and easy way to check and see if your digital camera sensor is dirty and needs a cleaning.
Above, some light spots of dust on a sensor. This was shot at using an aperture of F1.8.
Above, lots of dark spots of dust on a sensor, shot at an aperture of F22.

To check you sensor like image 2, put your camera on AV/aperture priority mode and stop down your aperture as small as it will go. Then, point your camera at a clean, blank, white wall (or sheet of paper) and take an image. If you have any visible spots on your image, that are in the same spots on both test shots, then you probably have a dirty sensor. If your camera has a sensor cleaning function, then run the in-camera cleaning. If not, or if the cleaning does not remove the spots, you may need an at-home cleaning kit, or to have a professional clean it.

Some other instances when you might see spots, but it might not be actual dust: damage to your lens itself, or a damaged sensor itself. The best thing to do would be to check with a repair shop if you're having issues. The KEH Repair Center offers professional sensor cleanings, lens cleanings, preventive maintenance care and much more!

Another thing to keep in mind is that sometimes it is impossible to remove every single speck of dust. So, if it's full of spots like the circled image above, have it cleaned. If there's one tiny, faint spot, it probably isn't worth the cleaning and may not even be able to be removed. This is why preventing the dust in the first place is extra important.
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