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.

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.

Canon Rebel XSi - 450DEvery year the photo industry whose aim is to make money just as the rest of us, is trying to seduce us into buying new gear and discarding the same equipment that was so hot just a year or two ago. Pumping out Megapixel monsters with features that rival those of pro cameras, they tell us that we have to have these wonderful new items. I admit, I am a sucker myself. Every time I open up a magazine and see the latest Megapixel monster staring back at me from glossy pages my heart beats faster. Of course, I read the testimonials from the "pros" (probably endorsed by the industry) who rave about the new technology. Looking at their fantastic images, we might think that we can only succeed with these tools. I am even thinking about upgrading my truly wonderful Canon. I am waiting for the 50D to hit the shelves and I might just buy the Rebel XSi in the meantime to have something new to play with, because I need toys to be happy.
On a more rational note, it is unnecessary to buy new equipment. Already the sensors of the last generation of digital cameras are pushing the limits of diffraction. The Rebel XSi will have a greater pixel density than any other camera with APS-C sensor size. This means that the maximum tolerable circle of confusion for this camera becomes smaller.

This means that we become more and more restricted to the minimum size of our aperture (largest f-stop). In order to boost Depth of Field, a small aperture is necessary.

What is the significance of this?

For once, the higher resolution is not going to make things worse. At the best case, we will get a picture that is 2 times better when the resolution of the sensor is 2 times higher, but in most practical situations, the lens or the optical resolution will limit us somewhat. I think at some point we will get to a point of diminishing returns in terms of resolution, but the camera industry will still taunt us with megapixel numbers for quite some time.

Another way to grow resolution is by growing sensor size (full frame). However, those are extremely expensive to manufacture are much more demanding on the lenses, since they require a larger image circle with the same perfection.

In the future, the industry should probably focus on more pressing issues like increasing the dynamic range of their sensors. If resolution is really all that counts, we can always resort to stitching.
 

P.S.: Don't worry if this discussion was a bit too technical to understand. I will soon elaborate these things in greater depth.

Just a few years ago, I was following the online debate between advocates of the Digital SLR revolution and followers of film. At this time, I had already made up my mind with the purchase of my first Digital SLR, the newly released Canon 300D. A true marvel and ahead of its time, it was said to rival the quality of 35mm film cameras. Back then, the Canon 1Ds used to be the nonplus ultra of Digital Imaging technology. At 11 Megapixels and equipped with the world’s first full frame CMOS sensor it was the dream of many wannabe photographers (including yours truly) and a must for pros. Many agencies just started to accept digital pictures and required “at least” 11 Megapixels. At the time of its introduction, the 1Ds did cost around $8,000.

Canon Rebel XSi - 450D Soon, Canons new entry level SLR, the Rebel XSi will debut at around $800. It will offer 12 Megapixels. Granted the Camera does not offer the weather seals and Full Frame Sensor of the “old” 1Ds, but crop sensors have many advantages. The new features like liveview really make the XSi stand out. With the smaller image circle of a crop sensor, lens design becomes easier making lenses cheaper and lighter. Regardless of feature counting, pixel peeping and rich playboy coolness factor, the XSi is the best camera available to amateur photographers with features exceeding those of previous professional models. Its lightweight design, quiet and inconspicuous shutter operation, and general tourist appeal is a real advantage during street photography sessions. The loud clonk of my 20D’s shutter resulted in stinkeye on more than just one occasion.

Learn what it takes to take perfect photos in winter.

Extreme weather conditions are challenging to photograph. High contrast scenes and bright snow throw off your auto exposure. Cold weather and condensation can damage your equipment and batteries drain faster.
Whether you are trying to capture the beauty of icy winter landscapes or your children’s fun on the slopes, the challenges of winter photography require preparation. In this short essay, I am going to give you advice to help you coping with those situations.

Boats photographed with the Tokina wide-angle lens
 

For quite some time I have been thinking about getting a wide-angle lens. I decided to start my Christmas season early by buying aTokina 12mm - 24mm f/4 PRO DX Autofocus Zoom Lens. The lens is suitable for Cameras with crop factor like the Canon Rebel and xxD series (e.g. 40D) and almost all Nikon Digital SLR.

Using a wide-angle glass on my camera brings many new possibilities to be creative. I can hardly wait for Thanksgiving, so I can put my new lens through its paces. I have already shot some pictures with it and feel comfortable enough to recommend the lens to my readers.  The picture of the beach and the boat picture demonstrate the impressive field of view that this lens offers.  Even more amazing than that is the low distortion. At 12mm, I had expected a lot of it, when there is hardly any. I did not correct the pictures with PTLens, so what you see here is pretty much what came out of my camera. I only ran a couple of scripts for color saturation and did not do anything else on these images.

The sharpness of this lens is just as impressive. It is comparable with other Canon Lenses I own and easily satisfies the needs of today’s Digital SLR lineup. The images are crisp and the color rendition is superb. I wish I had gotten this lens a bit earlier instead of missing the creative choices it offers me.

I did discover some vignetting on one of my shots but I believe it is due to the Tiffen Circular Polarizer Filter that I bought with the lens. I shot the photograph with an aperture of 7.1. I have shot other pictures with similar settings using the polarizing filter without seeing any vignetting. The effect was light enough so that I could fix it in post processing.

Canon S3 IS I often get asked for recommendations for cameras.  When it comes to anything besides Digital SLR, I think that it doesn't really matter what you buy, as certain cameras in the same price range are always comparable. Recently I was looking for something smaller then my SLR but a bit more useful then my Point and Shoot, when I came across the Canon S3IS (IS=image stabilized) that I found for slightly below $300 on Amazon. What makes this camera so great is that it really sticks out from its competitors in that it offers some features the others don't.

I am not going to pixel peep or show you graphs of noise levels. I think its enough to say that the camera offers enough resolution (6 megapixels) for decent prints. Although it is not comparable in terms of noise to a more expensive SLR, having a small sensor has its perks. It makes it possible to have a 12x optical zoom (36mm - 432mm equivalent) in a small and cheap package that you would have to pay an arm and a leg for to get on a SLR (and forget about traveling with that gear).

Person Yawning - Canon S3 IS Mostly I was intrigued by the swivel screen, that lets me shoot from the hip and by the completely silent operation (after you turn off all sound effects), which lets me shoot in places I would usually not dare pulling out the SLR (airports, public transport).
I recently talked about my new found passion of candid photography . I usually prefer to be upfront and use my SLR (Canon 20D), but in some situations you need a little bit more stealth. The photo to the right was shot in the San Diego Trolley and wouldn't have been possible with a SLR. The guy was sitting 2 feet away from me and didn't even realize it when I took his shot.

The S3 has a bunch of features that you wouldn't expect from a camera in this price range (it was more expensive when it was introduced).
Among those are image stabilization (this is a must for a camera of this size with a reach of 432mm). The image stabilization should give you at least two stops to play with, but I have managed to get decent photographs at the far end of the zoom with exposure times as long as 1/60s.
The S3 has easy access to Flash Exposure Compensation (something that I had to teach my 300D a long time ago via a firmware hack).

Lets talk about firmware for a while. Many reviews I have read about the S3 would complain about the lack of RAW recording. A RAW image is the unprocessed data directly from your CCD. It offers many advantages, such as a higher dynamic range and better post processing capabilities (no white balance applied yet, as the colors haven't been processed yet).  You can find more about this in my Workflow Tutorials.
The good news is, that there is yet another Russian firmware hack available for the S3, that gives the camera RAW capabilities. I have tried it out and I have been able to easily install it on my SD card (the S3 supports SD and XD cards). I have enabled the auto load feature, that loads the hack upon power up. The beauty of this one is the fact that it won't overwrite the current firmware. When you switch off the camera, the hack will be erased from memory (no more worries about the warranty that I basically voided when I flashed the firmware of my 300D a long time ago).

Cowboy - Canon S3 IS The hack has many other useful features such as scripting capabilities. I can think of a million useful scripts like an improved DOF bracketing (that allows you to reshoot the same image with a different focal plane over and over again and combine them on your PC for unlimited Depth of Field). Another script that I have installed gives me the ability to shoot a series with programmable intervals (seconds to minutes) and unlimited number of frames (you can be even stealthier if you don't have to have your finger on the shutter release button, or set the camera on the table and let it take pictures all by itself).

RGB HistogramThis display shows the blended version, but you can also configure the histogram to show 4 channels (luminance, R, G, B) separate A full color RGB histogram, configurable display elements and a battery meter (for some odd reason not included per default) are some other very useful features that this hack gives you. When you consider the fact that not even my 20D has a full color histogram, you can appreciate the features you can get with this hack and this outstanding little camera.

As expected, the noise level is significantly higher then on my 20D (no wonder as the sensor is so much smaller). At ISO 80/100 the camera delivers good enough pictures (check the full resolution example below), but ISO800 is very noisy. I have still used 800, as a noisy shot always looks better then a blurry shot (IS only goes so far in darker environments).

If you are looking for a camera that gives you more creative control then a point and shoot, and that has many advanced features, check out the S3. Even though the S5 is already on the market, a moderate increase in resolution (8MP vs. 6MP) wasn't worth the higher price tag (for me, as I already have a high quality camera). The hack isn't available for the S5 either, so that made it a clear cut decision for me.

If you are not going to install any hacks and if you are looking for a small but powerful camera as your primary camera, you might want to check out the S5 too. If you are looking for a really affordable but powerful camera, the S3 might be for you.

For some reason Adobe Bridge doesn't show the ISO information, but Exiftool does. I am not sure whats up with that, but again for many non professionals it might not be an issue and if it is, you can always use Exiftool.

The Image below can be downloaded in full resolution and as a RAW file. You will still need the DNG converter or DCRAW to use the file, so please don't download it if you are not interested in using this feature (it consumes a lot of bandwidth). Rather click on the image to pull up the full resolution JPG file.