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.

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.

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.

We have now scanned and uploaded the first reel of my Dad's Bolivia Photos to the store. I am still working on streamlining the process. Now that we almost finished moving in to our new place and with the holiday season coming, I should find the time.

One day I went through my Dad's attic and ran across his collection of several thousand slides from years of business travel. I still remember vividly how he used to give presentations in my school, captivating my classmates with his stories. Back in his days, business travel used to be a real adventure. Our country was poor and travel restricted. Sometimes reaching a destination for him consisted of a week of hair-raising journeys, making for first-rate stories. Now his slides were collecting dust and fading away in the depth of time, eaten by acids and humidity.

Thanks to the wonders of modern technology, we can now preserve his photos. Last year I purchased a Nikon Coolscan Slide Scanner , hoping he would be able to digitize his work. It turns out that the computer needed an upgrade as well. When I visited my parents this year, we worked on the scanning process a bit, but I will still have to put together a computer system.

Being separated by almost 10,000 miles does not make things easier for us, but we finally managed to scan some test cases. Eventually my Dad will have the tedious task of scanning a load of slides, while I just need to run some Photoshop actions on them, or so I thought. It turns out, that most pictures will need some individual attention as well, to fix some blemishes caused by the ravages of time.

I am looking forward to digitizing his photos and going on a journey through time, comparing the old and the new. I will visit some of the places and compare photographs. This should be a fun project.

You can find some of his Bolivia Slides in my Store. (Smugmug offers me unlimited storage)

Canon S3 IS

Translate camera lingo into meaningful information by using this glossary.

While I was writing my last tutorial, I suddenly realized that I am using idioms throughout my texts, the meaning of which may be elusive. Therefore, I decided to start this glossary to help you understand.

D

I focused this “dictionary” on terms relevant to digital cameras.

AD Converter: The Analog to Digital Converter transforms the Sensor information (charge) into digital levels suitable for the digital processor.

AE Lock: The Automatic Exposure Lock holds the exposure settings (aperture, shutter) over a series of images. Panoramic stitches require locking exposure.

AF Servo (AI Servo): This keeps the focus on a moving subject. AF Servo is useful for sports and wildlife photography.

Aliasing: Refers to the stair stepping (jaggies) of diagonal edges in images when the resolution is too low.

Anti Aliasing: Technique to reduce Aliasing by softening of aliased edges through blending and averaging of pixel values. The resulting image will look smoother and more natural.

IPAQ Picture ViewerToday I am going to show you some mobile computing solutions for the Digital Photographer using a Windows Mobile powered Pocket PC.
You can use the Pocket PC as an ultra mobile RAW file viewer and editor, to calculate the Depth of Field and Hyperfocal Distance, to evaluate Exposure, take notes, attach voice notes to digital files or read a book while you are waiting for an event.
The possibilities are endless. You can do almost as much with this ultra portable solution then with a "normal" PC.

Unfortunately many vendors like Dell have withdrawn from this market, but you can still buy everything you need (often at bargain prices).

Hardware

A few months ago, I purchased a HP IPAQ HX4700 through an Auction. This is still one of the most powerful machines to date and has some features that I considered vital to use it as a portable photographic computing solution.
The features most important to me:

• Full VGA (640 x 480) resolution (the HX4700 is one of the few Pocket PC with that much resolution; it's 4 times higher than most "standard" PDA. The Display is 4 inches in diameter and is large compared to other devices.
• 624 MHz Intel Processor (this is still the fastest PDA processor on the market and is required for RAW file evaluation)
• Two Memory Card slots (Secure Digital (SD) card and Compact Flash (CF) card). This is important, since I can keep the SD card in the device for file storage and to install programs to (you need to do this, to keep the main memory free for image processing, otherwise it won't work). Since all my cameras (Digital SLR from Canon) use CF cards, I will keep the SD card in the device at all times. If your camera uses SD cards, use the CF card for your PDA. Many modern PDA don't even offer CF card slots anymore.
• WiFi connection (so I could check my website when I am on the road or research a location)

IPAQ SD and CF Flash CardsThe HX4700 was therefore a logical choice for me, as it had the most advanced features and would still have a very decent battery life, even though it has such a large display and fast processor. Just in case I also bought the larger battery extension pack, which I have never gotten below 70% charge after 5 hours of regular use.

Software

Photo Software

Resco Photo Viewer 2007 Thumbnail View
The IPAQ is in Portrait mode (vertical)All screenshots are just thumbnail views (since the device has such a high resolution). You can click any of the screenshot pictures for a full resolution view (make sure your browser doesn't shrink the vertical pictures) The pictures will appear larger than the display of the IPAQ, since computer monitors don't have the same pixel density.

I have often proposed shooting RAW if your camera supports it, for the added flexibility (white balance, sharpening ...) and the higher dynamic range. RAW is often considered less desirable because it needs special tools to view and convert the files into JPG files for printing and web viewing.

Today there are two programs that support reviewing RAW files on your Pocket PC. PocketLoupe and Resco Photo Viewer Professional. Since PocketLoupe isn't updated anymore, I will not review it here (it won't be able to support newer camera models).

Resco Photo Viewer Professional

Make sure you will get the Resco Photo Viewer Professional Version, since only this version supports RAW files (RAW, CRW, CR2, RAF, MRW, NEF, ORF, PEF).

Usually I open up a folder on the compact flash card and look at the content via the Thumbnail view to get an overview about what's on the card.
Basically the Resco Application supports all things you would expect from a PC Application like Thumbnails, Exif Information, File Information, Zoom, Rotation, basic editing plus it supports features that many PC Viewers don't have (but the photographer needs) like Histograms and RAW file support.

It can be a very useful tool for the landscape photographer to evaluate one's photographs. However often there is no time (the light changes fast, the situation has changed), so I use it mostly to review some photos in my hotel room or to convert and email some of them or even put them in the blog (I am too lazy to write an entire blog post on the PDA, but I could.

Resco Photo Viewer 2007 Screenshot Image view with Histogram (blue channel) Device switched to Landscape Mode (horizontal)

Resco Photo Viewer 2007 Menu Brightness Histogram and Menu Device switched to Landscape Mode (horizontal)