Etikettarkiv: sharpness

Shooting handheld with long exposure

As everyone knows the trick is to keep the camera steady and this is easier said then done. When the exposure times goes up to 1/30s and more most people run into problem. There is a simple formula you can use to calculate the slowest exposure for a given focal length and it goes like this:

t = 1/f

t is your exposure time (shutter speed) and f is the focal length you are currently shooting with.

Some people also say there should be a 1.5 factor here because of the crop factor of the APS-C sensor in most digital cameras. That’s not my experience and I believe the explanation is that the smaller the sensor, the less the camera shake is noticeable. Anyway, I have never had a problem shooting handheld with this formula.

This means that for a 200 mm lens you need 1/200s in order to shoot sharply handheld. This is a good aim but sometimes you can not get that because the light is not goot enough and you don’t want to bump that ISO setting because it produces far more noise in your pictures.

On a 50mm it says you should be able to take sharp pictures handheld down to about 1/50s which is a pretty low shutter speed. This is definitely possible but for the best result you can practice the McNally Grip, also known simply as ”Da Grip”. This requires you to be a left-eye shooter and is easier for right-handed people.

It’s not always practical to carry or even use a tripod. If you are doing street photography with a tripod in certain places you know the police may take an active interest in what about you are up to. Basically this is the same technique as when firing a rifle, you keep it well tucked in, steady and squeeze the trigger as you slowly exhale. Same thing here, just a camera trigger.

Ubuntu ColaUsing this technique most people can shoot about 1-2 EV lower than they would otherwise. This means that if you can just about do 1/50s with a 50 mm you may be able to get tack sharp pictures down to 1/25s or even 1/10s which is really really good!

This is handheld only in lamp light in the metro line of stockholm city (focus is deliberately on the Ubunty cola poster to the right hand side):

The reason I took this is because Ubuntu is also a Linux distribution.

I happen to be both so I love this.

McNallys blog post here >>>

Or you can watch his video here directly if you like.

The Difference Between DX and FX Lenses

Sometimes people ask questions on what the difference is between DX and FX lenses. DX and FX are Nikon lingo in specifying different sensor sizes on cameras.

On digital cameras Nikon have traditionally employed what they call DX size sensors. This sensor was originally a CCD type sensor such as the one in the D70 camera and has later been replaced by a CMOS sensor on the later versions such as D200 and later cameras.

Before we all went digital a ”normal” prosumer or semi-pro camera was almost always a 135 system camera. This means we had 35 mm film in the camera and the projected image was usually 24×36 mm onto this film. With the invention of the APS-C format sensor which is 23.7 x 15.5 mm in size this format was known as DX. They are all small format cameras.

Because the digital bodies, with the exception of the so called ”full frame” bodies, have a much smaller area onto where to project the image from the lens, it is possible to make cheaper and lighter lenses by sacrificing the area outside the sensor. The result is a special line of lenses called ”DX” lenses.

Canon, Sigma, Tamron, Tokina… they all have their own respective way of denoting lenses that are ”optimized” for digital DX format cameras. But what happens if you mount a DX lens on to an FX body and start taking pictures?

In the worst case you would get completely black corners. Because the ”full frame” sensors are bigger parts of them may fall completely outside the projected image by the sensor, something that would lead to black corners.

In many cases it would not be so dramatic but instead you would see some vignetting, the falloff in light in the corners and in all cases you can be pretty certain that sharpness, chromatic aberration and so on will not be very good in the corners of the picture.

Here is a demonstration of the difference and why it may be difficult to use DX lenses onto the new types of digital cameras with larger sensors, results will vary depending on the actual lens, some DX lenses work better but never as well as a lens actually designed for FX format cameras.

This picture shows an extreme case of vignetting where the image from the lens fails to cover the whole sensor of the camera. This can happen for example with extre wide-angle lenses designed for DX cameras and mounted onto FX bodies.
This is a more normal result of what most DX lenses would produce on FX bodied cameras, the falloff is more graduated and could still be useful.
Here is the lens used on a DX format camera. Note how the crop factor of the camera "crops away" all the vignetting of the lens.

By not having to design lenses for the full FX format the manufacturers can make do with smaller lenses, this means they can be lighter (good for hiking photography) and they can be made cheaper.

How about using FX lenses onto DX cameras then?

That works exceptionally well! Because of the crop factor the DX body will use only the best part of the lens, usually the middle of the picture is sharper and more defined than the edges and if the edges are cropped away because of the smaller sensor you will have excellent sharpness all the way out in the corners of the picture!

So there are definitely advantages to the DX type bodies, that should not be forgotten!