Diffraction affects your image sharpness by limiting Depth of Field and useful Resolution. See how our camera and lens choices influence these limits.

To increase Depth of Field we simply decrease aperture (larger f-stop). However, we cannot get infinite Depth of Field by decreasing our aperture infinitely. Diffraction establishes the upper limit to Depth of Field.

The subject may seem very technical, but the solution is far from being difficult. To understand this tutorial better, consider reading my Correct Exposure Series of Tutorials and my previous tutorial on Hyperfocal Distance, which explains the relationship of aperture and Depth of Field.

Diffraction is an optical effect limits the resolution / sharpness of our photograph. Since it is an optical effect, higher resolution sensors will not improve resolution further. Higher resolution cameras are thus more demanding on our optics and eventually will yield little to no improvement in total resolution. Diffraction plagues landscape photographers who are striving for a large depth of field and high-resolution images. Many of us are not even aware of this, blindly selecting a small aperture according to our calculators and charts.

Canon Rebel XSi - 450DMy brand spanking new Rebel XSi arrived from Amazon Today. I finally have a new Toy but I promised to wait for my Birthday that is right around the corner. I already drew up a series of tests I am going to subject the camera to to compare it to my previous models and to test the resolution limit. Until I am ready to unpack my new toy (and get a year older), I have a tutorial to upload.

It has been a short while since my last tutorial since I have been busy with my failing computer and data recovery.

Finally this was over when Tina scared us out of our minds. We had to take her to the emergency care and get her checked out. Tina is our beloved Tabby Feline. Her sibling brother Tigger died almost exactly 2 years at the tender age of 4 and 11 months (yes their birthday coincides with mine). It was heartbraking and it is hard to learn that Tina's days are precious as well, as she has been diagnosed with an illness that could cost her dearly one day. We took her home with us after 2 days of emergency care.

I am a soft hearted person and when it comes to my baby Tina I am just a big sucker.

Back to business: I am probably going to write a 450D diary, adding little pieces of information as I am using the new camera.

The Culprit: Broken 80GB Wester Digital DriveThree to four weeks ago, I got the shock of my life. I turned on my main Photoshop Computer that also holds all of my photographs in form of undeveloped RAW files. Suddenly my computer reported that it could not find any hard drive to boot from and it made loud clicking noises. One of my drives was trying to spin up but could not. It sounded very much like a head crash.

The next day was pure agony for me, when I had to wait to dissect my computer. Although used to back up everything to external drives, I had become lazy recently. My most recent backup was already several months old. I took my internal hard drive to usb adapter and hooked up my main picture drive to my computer. The adapter works with Laptop and Desktop drives as well as the new SATA drives.

The dictionary (Webster) defines photography as "the art or process of producing images by the action of radiant energy and especially light on a sensitive surface".

This means that we create our images by capturing light (photons), reflected from our subjects, with some sort of detection device. That means we will not be able to capture anything in absolute darkness.
Landscape photographers usually rely on the sun as their source of light, but creating our own source of light at night is not a new concept. Painting with light simply means that you brought your own light source and that you choose what to light and what not.

On my last trip to Mono Lake, I thought that the bizarre shapes of the lake would lend themselves to this technique. After the sun set, I set up my camera on a tripod and chose an exposure of around 30 seconds, so I would have enough time to sweep as much of the landscape with my spotlight as I needed. I used a mid range aperture setting of around f-8 to start and adjusted the aperture accordingly after the first shot. You have to use manual settings, as the camera cannot evaluate the scene correctly with the spotlight. You need about 20s-30s to evenly paint a scene with a strong spot light.

Driving through California is one of my greatest joys. On my way to the great photographic sights, I have plenty of time to think about how California really looks like apart from the glossy pages and polished frames people are used to seeing. One of the main sights on my travels are golden hills lined with trees. Depending on the time of the day, they may glow golden or look rather dull and brown.
For some reason, I always pass the most beautiful rolling hills in perfect light when there is no way to pull over. This is pretty much how most of central California between I-5 and 101 looks like. I am sure that I will finally succeed in capturing a better image.
 

Split Neutral Density Filter (c):kodak.comLandscape scenes often contain more dynamic range than our cameras can capture. Even though digital cameras have increased their resolution tremendously, the dynamic range they can capture has not changed much over the years. Fuji has introduced the Super CCD SR to extend the dynamic range, but the technology is expensive and has not been adapted throughout the industry.
Split Neutral Density filters are one solution to this problem. They regulate the amount of light hitting the image sensor. A Split Neutral Density filter works like graded sunglasses for your camera. The gradient will make sure that there is a smooth transition between the shaded and the clear area.
Usually one would use these filters with the darker area covering the sky, to reduce the brightness levels there and reduce the dynamic range of the scene to something the camera can manage.
I do not use these filters anymore for their many limitations. The transition is usually on a straight line, which works well for reasonably flat landscapes with a clear transition between sky and land. In other cases, this is not the case. I would not use a split neutral density filter to shoot an alley, a tunnel, or a city skyline (a fact that bit me in this shot).
Another big drawback is that you need too many of those filters, depending on your focal length. Wide-angle shots require a much smoother transition, since your lens covers a much wider area. Telephoto lenses require filters with a much harder edge.
These days I usually take multiple exposures or try to recover as much dynamic range by processing my RAW files through HDR software.
If a scene has no movement and there is plenty of time to set up a tripod, I always prefer to take multiple exposures. During post processing, I can create any kind of transition with any shape I want. Even easier is to run these images through the same HDR program. This is what I did for this image of False Kiva.

Monday is Saint Patricks day, where all Irish communities around the world celebrate one of the patron saints of Ireland. The San Francisco Bay area has a large Irish community and hence Saint Patricks Day has always been celebrated with fanfare.

Yesterday San Francisco kicked of the St. Patricks Day Celebration with a big parade. I took this chance and tried to capture the spirit of the day.

See some of yesterdays pictures in my St. Patricks Day in San Francisco Gallery.

Determining the "correct" exposure for an image can be a challenging task. We could choose to simply let our camera decide for us, and use the fully automatic settings that are quite sophisticated and often do a reasonably good job. However, this also means to give away part of the creative process to your camera. I am writing this tutorial with the beginning photographer in mind. The principles outlined in this article should become a second nature to you. I encourage you to practice and to ask questions. In many ways, this is like riding a bike. Once you learned how, you can focus your attention on your surroundings.

I am not advocating using the manual settings of your camera at all times. Instead, I am a big fan of the creative zone settings such as Aperture Priority Mode, Shutter Priority Mode and Program mode. I use these automatic modes 95% of the time and I rarely resort to Manual Mode.

Aperture settings determine the Depth of Field (how much of your scene is in focus). Landscape photographers often strive for a very large Depth of Field while Portraits often require a shallow Depth of Field. Being in control of the aperture, the photographer can direct attention and guide the viewer through the image.

Shutter speed controls how motion of the subject or your camera will look like in your pictures. A slow shutter will blur fast moving subjects and a fast shutter will freeze them.