Tag Archives: lens

Tilt-shifting at windmills (and other tall buildings)

What does “tilt-shift” mean to you?

Get that thought out of your head right now. Yes, tilt-shift lenses CAN be used to do that, but there’s so much more to them. To start with, the above effect was created in Photoshop, but when you tilt a lens in the opposite direction you can actually achieve a WIDER depth of field by aligning the focal plane with, or close to, the ground, without having to stop the lens down to f/11 or smaller. But that’s not why I use these lenses.

Take a look at this photograph of the railway arches near where I live:

It was taken with a 17mm lens from ground level, meaning that to include the top of the viaduct in the photo I had to tilt the camera back. With a rectilinear (i.e. not fisheye) wide angle lens, this has the result that all vertical lines start to converge, distorting the shapes in an unpleasant, almost vertiginous manner.

Luckily, the 17mm lens in question has a shift feature (the tilt wasn’t used for the next shot). So I shifted the lens upwards and aligned the back of the camera to be parallel with the walls of the viaduct:

Now the vertical lines on the structure are vertical in the photograph, and yet I still have the top of the viaduct in shot. This is because the 17mm TS-E lens has a much larger image circle than a standard 17mm lens. When you shift the front element upwards, the image circle also moves so that the portion that hits the sensor is towards the top of the scene. Using the same lens but without shifting would have resulted in a photo with only the bottom portion of the arches in shot, and far more pavement than would be reasonable.

This shot of Watford Fire Station was taken with the lens shifted up partially, meaning the building is centred vertically in the frame, rather than towards the top:

_MG_0279An extreme example (when you stand a bit closer to a building than is strictly necessary) shows how the perspective towards the edges of the larger image circle can be a bit overblown:

However with a slightly less wide lens (24mm in this case) and a building that’s further away, shifting the lens can result in very pleasing ground-level shots of tall buildings:

Apologies for the lack of windmills in this post. I just couldn’t resist the pun.




One of the questions you may ask yourself when deciding to buy a digital SLR for the first time is ‘Full Frame or cropped sensor?’ Even if it isn’t, it should be. The obvious next question is: what’s the difference? Well, it’s more complicated than you might think.

A full frame (‘FF’ hereafter) camera has a sensor that is the same size as a frame of 35mm film (36mm x 24mm); so-called ‘cropped sensor’ (‘CS’) cameras have smaller sensors, though there is no single standard, for example the sensor in a Canon EOS 550D measures 22.3mm x 14.9mm whereas in a Canon EOS 1D mk IV it’s 27.9mm x 18.6mm. Generally, FF cameras cost considerably more than CS models, however you might be able to pick up a second hand Canon EOS 5D or Nikon D700 for a reasonable price.

Many people talk about the ‘magnifying effect’ of a CS body. I find this term misleading; any magnification is done by the lens, and a 50mm lens is a 50mm lens on any camera. The image projected onto the sensor plane is identical, but the smaller sensor means only a part of the image is captured compared to a FF camera. To physically print the image would require more magnification but this is applied after the photograph is taken, and so is not technically a function of the sensor.

This also means that to get the equivalent field of view in a CS camera to a 50mm lens on a FF model, you would need to user a wider lens, eg 35mm, though the exact focal length would depend on the physical dimensions of the sensor. Using a lens with a shorter focal length means you get more depth of field, so this is one of the first things you need to think about when choosing sensor size; does your style of photography require narrower or wider DoF? Below 35mm though, it must be said, DoF is generally so wide that it makes little difference.

Cropping the image also means it is easier to fill the frame with a subject, especially useful in wildlife photography where small animals are shot using telephoto lenses of 300mm or more. This is where it is beneficial to use a smaller sensor; while it is also possible to crop a FF photo in post processing to achieve the same effect, you end up wasting pixels and losing detail as the resulting resolution is so much lower.

Using a full frame sensor it can be harder to fill the picture with your subject
Using a cropped frame sensor, your subject fills the picture more often (note: this is a crop of the photo above, and was not taken with a CS camera)

Of course the converse applies to wide angle lenses. Much of the drama of a good landscape comes from using lenses of 20mm or less, and when the extremes of a photograph are cropped out, this added drama can be lost. Unlike with telephoto lenses however, you cannot reverse the effect in PP.

With a full frame sensor, the full effect of using a wide angle lens is attained.
Using a cropped sensor, the dramatic extremes are lost (note: again this is a crop of the above photo and was not taken with a CS camera)

The one final consideration is image quality. Generally, except for the most expensive lenses, this deteriorates towards the edge of the picture, so by using a cropped frame sensor you are eliminating the less well defined areas of your image meaning you don’t necessarily need to spend as much on good quality glass. On the other hand (though this is less true with the latest developments in sensor technology), the high ISO performance of CS cameras is not as strong as that in FF cameras. This is because the pixels are more densely packed in a CS camera, and so are smaller and more sensitive to non-optical factors, such as electronic interference caused by the camera’s own circuits.

It is not my intention to say what is right or wrong, as I don’t believe there is such a distinction. But if you are fully aware of the consequences of your choice of sensor size, hopefully it makes it easier for you to make the decision that works for you.

Nifty fifty

It’s been said that you’re only 50mm away from becoming a better photographer. Time was when pretty much any (film) SLR camera you bought had a 50mm lens strapped to the front, often with a maximum aperture of f/1.8. The thing is, a 50mm lens is at the sweet spot where the image quality to cost ratio is at its highest. However these days, most kit lenses that ship with even the most expensive DSLRs are so poor that they are hardly worth bothering with. Most people, though, are unaware of this, and continue to use sub-standard glass and wonder why their pictures never look like how they remembered them.

I have attached here a selection of my favourite shots taken with my trusty Sigma 50mm EX-DG Macro – a lens that cost me £200 and is as sharp as lenses that cost five times more.

Low light, low noise

I’m thoroughly enjoying getting to know the new camera, and in conjunction with Sigma’s increasingly impressive 105mm EX-DG Macro I am getting some very pleasing results. Here is a set of pictures taken at lunch time today at London’s famous Borough Market, a food market selling fresh, high-quality and expensive food. Every single picture in this set was taken at ISO 3200, and the colours you see are just as the camera recorded them.

After returning from the shoot I had a message from Jacobs that my new battery grip had arrived. So, with today’s release of the Camera Raw update for OS X, I now have everything in place for a complete EOS 5D Mark II workflow. All I need is to take some more pictures…