Taken in Saltsjöbaden, Stockholm, Sweden using Nikon D70s and Nikkor AF 50/1.8D. Post processed in Adobe Lightroom.

One of the greatest things with a SLR type camera is that it is possible to control the focus in the picture. This area is known as the DOF or the Depth-of-Field, or the Depth of Focus. This the space in a picture where things are in focus. In front of the DOF is the near out of focus field and beyond is the far out of focus field. There are certain things that controls this field and this article will describe them and how you can use them to improve your pictures. Without going into the actual optics, I will try to explain how to achieve the desired DOF and what it can be used for.

What affects DOF?

The DOF is actually the part of an image that is in focus. Any lens have a certain volume where things are percieved to be in focus and this volume or field of focus is referred to as the DOF. There are several factors that influences this, one of the most important factors is the aperture setting of the camera.

The aperture

The aperture controls how much light that falls into the camera at a given moment, it is a diaphragm in most cameras it is located inside the lens or just behind it, in the SLR type cameras it is located in the detacheable lens that is part of a camera system.

The aperture can generally be set in several steps. Earlier lenses permitted a limited number of steps but modern lenses and digital cameras permits the aperture almost always to be set in steps of 1/3 of a EV. The aperture is expressed as a ratio between the focal length and the diameter of the diaphragm and therefore it is written as f / 5.6 for example.

Cheaper lenses have a more narrow range of apertures than more expensive lenses, this means you can “open up” the aperture more on the expensive end, this is sometimes called “fast” lens (because they give shorter shutter times for the same scene during same conditions as a less expensive lens does) or more “sensitive”.

If you are using a good lens and you are setting it to the  lowest f-stop permitted then you will have the most narrow DOF that this lens can produce. This is a start and a setting you might want to use during low light conditions but remember that your shallow DOF can make it difficult to get the full scene in sharp focus.

The focal length

The focal length plays together with the aperture of course as we have already talked about. The focal length is what you “zoom” to when you zoom, or the fixed focal lenght of your prime lens. The smaller the focal length, the wider the field of view and the deeper the DOF becomes.

The greater the focal length, the more you “zoom in” the shallower the DOF becomes.

The focus point

The focus point is the last part of our equation. The closer to you the focus point lies the shallower the DOF is. The further away you focus the deeper the DOF will become.

It is all about rations between these three, the aperture, the focal length and the distance of the focus point. If you want to create a shallow DOF you should open the aperture, zoom is as much as possible, go close as much as possible and then focus closely.

Remember also that most of your DOF is behind the point of focus, when you focus on somethin the DOF arranges so that you have 1/3 of the range in front of your focal point and 2/3 behind it. Make use of this!

Portraits

This is used in portrait photography to create a sense of depth in the image. Typically you see the model in sharp focus and the background cast in blurriness, this is due to using the DOF properly.

Portrait optics are usually in the range of 90-135 mm focal range and can often be used with an aperture up to f / 2,8 which allows the photographer good control over the DOF and to photograph in the low light of dawn and sunset.

Hyperfocal charts

Finally

These are the things that affects your DOF:

• Focal length
• Aperture setting f / x
• Distance to focus point

When you focus on something the DOF extends 2/3 beyond that point and 1/3 in front of it.

Battery Charge

Table is given for 20°C.
Adjust table with 0.022V/°C when deviating from this temperature.

Unloading-end: 11.8V, charge with 13.2-14.4V. Battery will start gassing at 14.4V (do not exceed). Continuus preservation charge max 13.2V. Float charge; 13.4V for gelled electrolyte, 13.5V for AGM (Absorbed Glass Mat) and 13.8V for flooded cells.

Precision of charge voltage is critical to keep sulfatisation at a minimum. An error of 5% may be enough to reduce life substantially.

A newly charged battery will quickly drop to 13.2V and then slowly settle at 12.6V. After full charge let battery rest 20 hours before measuring open circuit voltage. There might be residual surface charges on the conductor plates otherwise.

Equalization charge – maximum 2 hours at 15V. Make sure ventilation is good and battery temperature is constanly monitored.

A little while ago I found this excellent blog on Nikonians by Martin Turner. He writes about how the classic potratit painters worked and how we can improved our portrait photography by learning from these masters. He has written several very interesting blog posts on this subjects and I felt like commenting on them myself.

In his first post also titled “Learning about portraits from the masters” he discusses the context of the portrait more than the actual technique to pain or photograph. A portrait is supposed to say something about the person being portrayed and therefore it is important to not lose context and pay some attention to the surroundings of the person, the positioning of the subject, any other props or objects in the picture should have meaning and add to the portrait and not detract from the person being potrayed. I think this is an important lesson and something that is easily forgotten.

In his second post he speaks about differential focus something that has been used by painters for a long time and photographers using a telephoto lens, wide open aperture and focusing as close as possible to re-create. Of course post processing can also be used to achive this and there are more than one way of doing nice differential focussing on a subject.

For a portrait we want the eyes to be sharp, then the mouth and the hair are also important — putting too much fuzziness on the hair makes things look strange and the eyes and mouth are what we as humans focus mostly on when we are viewing a portrait of someone else. An excellent example about this is the painting of a Genoese nobleman painted by Bernardo Strozzi in oil on canvas.

Another thing that he notices are also that backgrounds in paintins are almost always very dark. Almost to the point of being black but never completely black there is always some texture to them but in a very subtle way and the idea of isolating the person from the background is very evident.

Today in photography we often use light backgrounds, even white overexposed so called high key shots which usually means you put 4 times as much light on the background as you do on the subject. Makes it easy to cut out in photoshop and re-arrange in a different background but I get a feeling there is a reason that portrait painters never used such backgrounds.

He also talkes a lot about skin details and softening of the skin in portrait. This was done by painters also using selective focussing techniques when painting but this is also likely down to that our minds generally don’t remember much skin details, we focus on the areas around the eyes and mouth and we tent not to remember too much on other details.

The rest of the posts are also interesting but his number 2 post was the best one so far in my opinion.

You can find Martin Turners Nikonian blog here if you want to read more, and I hope you will because it is very interesting to read his articles!

Some of you already know my fascination for wrist watches and therefore I thought I should share with you my latest aquisition, the Suunto Core outdoor wristwatch. Suunto is Finnish and means direction and this is a good name for these watches. There are many different models to chose from and I decided to get the Suunto Core model which seems to get you lots of functions for small money and the most all-round watch there was. Or, sorry, wristtop computer as these watches are sometimes referred to.

I am a guy who like walking in the woods, hiking, trekking and just generally being outdoor when possible especially in the summer time. I try to make at least a few day trips and if possible an overnight in a tent as well every summer as a minimum, it is something special when you are cooking in the wilderness, sleeping in a tent and generally having to struggle a little more than you normally do every day to and from work. If nothing else you appreciate a nice bed when you come home again

On top of that I am an unchangeable gadget-guy, and I really enjoy knowing the altitude I am on right now, the bearing I am walking in, my position, the time, when the sun rises and sets on the latitude that I am right now and many other things. So my latest addition to things I won’t leave home without now is a Suunto Core wristwatch.

This little gem can do a lot of things and it is a watch specially designed for outdoorsmanship more than anything else. This is not the first “trekker’s watch” I have owned, I also have an “Origo” watch but after a particularly rough outing in the United Arab Emirates a couple of years ago the altimeter broke on that one. So I have decided to get myself a new watch and now I recently bought it.

The Suunto Core watch keeps two times, good for traveling and it has what you expect from a modern digital watch, countdown (99 min max) and works wel as a stopwatch (24 h max). On top of that you can program it with the closest city and it will show the time the sun rises and sets for the date, something that changes drastically right now, the day becomes longer with about 6 minutes every day now and the nights shorter here in Stockholm.

The watch also contains three interesting functions for the hiker not normally found on wrist watches and they are altimeter that shows how high over the sea you are at the moment, barometer showing the air pressure (sea level equivalent) and an electronic compass.

Suunto Core, outdoors sportswatch

The altimeter and barometer are actually two faces of the same coin here. You can select the profile yourself, if you want the watch to be in altimeter mode when you climb, then you can set it to barometric mode when you stop for the night and the watch will tell you the air pressure and assume that you are staying on the same level. You can not get both at the same time though because both the barometer and the altimeter works from the same air pressure sensor. If you climb a mountain the air pressure lowers with every meter you climb, the watch senses this change in air pressure and can therefore know how many meters you have scaled. In barometric mode you fix the altitude and the watch instead registers the changes in air pressure that preceeds an oncoming storm or weather front.

The watch can automatically shift between altimeter and barometer mode, it understands when you start climbing because the air pressure shifts too fast and then it switches to altimeter. If you stay it will after 12 minutes of no change in the altitude (or very small changes) shift back to barometric mode. Brilliant. Over a full days walking around I generally don’t have to recalibrate it for more than 20-40 meters error by the end of the day.

In barometric mode it can also tell you if there is a sudden drop in air pressure. This might signify an oncoming sqall or storm and you can set an audible and visible alarm on the watch to go off if this happens. There is also a 24 hour trend graph that will show you the changes in barometric pressure over the last day and night. There is also an arrow indicator showing you if the air pressure is stable, tends to rise, tends to drop and the attitude for the last 3 and 6 hours. Great for checking if the current weather is stable. I have observed the barometric pressure alarm go off twice. In both accounts it started snowing heavily hours later so I believe it is working pretty well!

The last function of the pressure gauge is the “snorkeling feature” where it can tell you when you snorcle in the hot waters of the Maldives or some other nice place how deep you have been as maximum and how deep you are now. Not quite a diving instrument (watch should not be submerged more than 10 meters really) but it is still a pretty fun feature.

A logging function can be used to keep track of your climbing and descending over time if you want. It will log the altitude and the current time as often as you want and you may also save the log for a later review. You can also set a reference altitude and the watch will show you how much above or below your reference you currenly are.

You can also have it show accumulated inclines declines, something that I thought was pretty neat in a ski slope…

There is also a temperature measurement but since the watch is warmed by your arm it generally does not show air temperature. If you take your watch of and leave it for 30 minutes or so it should give you a pretty good temperature reading though. The temperature is also necessary for the accuracy of the air pressure measurement.

The compass is great, works well but uses battery more than other thngs and because of this the watch will turn it off after one minute of operation; you will then have to press a button to turn it on again for another minute. If you have the backlight lit during compas operation it will flash as it goes dark for each measurement that is done – about 2 per second. The compass can be set to try to stay in a certain direction, it will show with arrows how much in error your current direction is and point you in the right direction and the precision is actually pretty good in the woods. Calibration is simple, turn it on, slowly spin a full circle clockwise and it will recalibrate itself. In urban environment there are sometimes problems where there are heavy electrical machinery and other ferro-magnetic materials at work that will confuse it – try looking at it while a metro train in the underground drives past… but most of the time it can be used there as well.

All in all I really love this watch. I recommend it for everyone who loves to be outdoors, hiking, fishing, hunting, climbing, skiing… this is for you!

I rate it 5/5.