Friday, February 24, 2017

Aperture Explained Part 2

In the last article of this series we looked into how the aperture was defined and how it influenced the depth of field. Today we will look into how the aperture, together with the shutter speed and the ISO, helps you to get the right exposure for your photo.

The Exposure Triangle


The aperture defines, as we have seen before, how far open the opening in your lens is to let light pass through. The shutter speed defines how long the shutter curtain is open. The longer you open up the shutter curtain the more motion blur you will get and the harder it will become to handhold the camera without accidentally adding motion blur. The general rule is to keep the shutter speed at 1/(focal length) or faster when you are shooting handhold, and it should in almost all circumstances give you a chance to hold your camera steady while the shutter curtain is open. If you need a longer shutter speed, you should either use a tripod or a beanbag to keep your camera steady1. To photograph a fast moving object–say a racing car–tack sharp you would want a high shutter speed, but when you are photographing landscapes you can often go for a longer shutter speed as landscapes don’t have a tendency to move away.

Since a subject needs a certain amount of light to be exposed correctly onto your sensor or film, one could believe that all you need to take care of for a correct exposure are shutter speed and aperture, but there is one more important setting to take care of: the ISO.

In the analogue era, films were produced with different light sensibilities, the sensibility was marked on the package as an ISO and/or ASA value. In the digital era the sensibility of your sensor cannot be changed–you thankfully don’t have to replace your sensor every time you need a different sensibility–instead a signal enhancer is added, so that when you dial in an ISO of 400 for example the signal enhancer will make sure that the sensor records more of the available light than with an ISO 200. A higher ISO value will however not only enhance the signal that reaches your sensor, but it will also lead to more grain in your photo, so generally you want your ISO as low as possible.

The doubling of the aperture, shutter speed or ISO changes the exposure by what is called 1 stop. So a shutter speed of 1/250sec is one stop faster than a shutter speed of 1/125sec. If you changed the shutter speed from 1/200sec to 1/60sec you would get a two stop slower shutter speed. Changing the ISO from 100 to 800 means a change of three stops (ISO 100 -> ISO 200 is one stop, ISO 200 -> ISO 400 is a second stop and ISO 400 -> ISO 800 is the third stop).

So say you have a perfect exposed photo at F/8, 1/100sec with an ISO 100, but what you would like to do is to have less depth of field.
 To achieve less depth of field you would want to use a wider aperture, which allows more light to pass at a given time as we have seen in the first article of this series. If you wanted the same subject photographed with less depth of field and you concluded that F/2.8 would do the trick for you, how would that change the shutter speed and ISO? Remember the aperture-value table from the first article?

F/2.8 means adding 3 stops to the exposure, so now you would need to subtract three stops from either shutter speed, ISO or a combination of both. Since we are already on the–for most cameras–lowest possible ISO, in this case we would change the shutter speed. Subtracting three stops from the shutter speed means making it three times faster, which results in a shutter speed of 1/800sec (1/100sec -> 1/200sec equals 1 stop, 1/200sec -> 1/400sec equals the second stop and 1/400sec -> 1/800sec equals the third stop).


Let us collect our findings about changes of one stop for the shutter speed in a table.


Starting shutter speedNext slower shutter speed
(1 stop slower)
1/4000sec 1/2000sec
1/2000sec 1/1000sec
1/1000sec 1/500sec
1/500sec 1/250sec
1/250sec 1/125sec
1/125sec 1/60sec
1/60sec 1/30sec
1/30sec 1/15sec
1/15sec 1/8sec
1/8sec 1/4sec
1/4sec 1/2sec
1/2sec 1sec
1sec 2sec
2sec 4sec
4sec 8sec
8sec 15sec
15sec 30sec
Figure 1: Shutter speed one stop apart



And let us do the same for the ISO


Starting ISONext higher ISO
(1 stop difference)
ISO 100 ISO 200
ISO 200 ISO 400
ISO 400 ISO 800
ISO 800 ISO 1600
ISO 1600 ISO 3200
ISO 3200 ISO 6400
ISO 6400 ISO 12800
ISO 12800 ISO 25600
ISO 25600 ISO 51200
Figure 2: ISO one step apart


Now let us have a look at some photos that will make use of these changes. I have taken the photo of the pear on the fence always from the same distance, and all of the following photos are taken with the same focal length. So the changes in the depth of field are only related to the changes in the aperture. To make the examples a little easier to follow I have never changed the ISO in between photos, so the exposure is only achieved by changing the aperture and shutter speed.


As you can see the photo is tack sharp from front to back, and it has a high depth of field, caused by the narrow aperture of F/22. But despite this being a bright day, the shutter speed is at a slow 1/15sec–something you would most likely not be able to handhold. So what happens if we widened the aperture by one stop to F/16?


To get the same exposure we had to double the shutter speed. This still gives us a tack sharp photo from front to back, so let us see what happens if we changed the aperture to F/8 instead:




As you can see, with an aperture of F/8 we had to quadruple the shutter speed to get the same exposure, compared to the photo with the F/16 aperture. But we still have a rather high depth of field. What if we wanted a lower depth of field? Yes, we would open up the aperture even more, say to an F/4:


Since we opened the aperture with another two stops we have to quadruple the shutter speed again, so that we now have a shutter speed of 1/500sec. And as you can clearly see in this last photo, the depth of field is significantly shorter, leaving the background and parts of the foreground blurry while our subject–the pear–is still in focus.

So let us collect these findings–and I will add some ISO changes that we haven’t looked at in these example photos–in another table:

Aperture Shutter Speed ISO Focal length Depth of field
F/22 1/15sec ISO 100 55mm high
F/22 1/30sec ISO 200 55mm high
F/22 1/60sec ISO 400 55mm high
F/22 1/125sec ISO 800 55mm high, grain might occur due to the ISO
F/16 1/30sec ISO 100 55mm high
F/16 1/60sec ISO 200 55mm high
F/11 1/60sec ISO 100 55mm high
F/11 1/250sec ISO 400 55mm high
F/8 1/125sec ISO 100 55mm high
F/5.6 1/250sec ISO 100 55mm lower
F/4 1/500sec ISO 100 55mm low
F/2.8 1/1000sec ISO 100 55mm low
F/2 1/2000sec ISO 100 55mm low
F/1.4 1/4000sec ISO 100 55mm very low
F/1 1/8000sec ISO 100 55mm very low
Figure 7: Working exposures

Since the correct exposure of a photo is reached by adjusting three values–the aperture, the shutter speed, and the ISO–it is commonly referred to as the exposure triangle.


Next time, on March 24th 2017, we will look into the dependencies of focal length, aperture and depth of field.

1 While using a tripod you should also deactivate Vibration Reduction / Shake Reduction from your camera or lens. Also you should use a remote trigger or at least the self timer of your camera with some delay, so that you don't accidentally move the camera–just pressing the shutter button can add a tiny amount of movement to your camera–while the exposure is ongoing. Back to text



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Friday, February 17, 2017

The Scandinavian Adventure: A day off in Copenhagen

(Monday, July 14th 2014)

Our plans for the day were easy, all we wanted to do was some sightseeing in Copenhagen before we would get back onto our bikes the next day. Unfortunately the weather was again not on our side, so that we borrowed some umbrellas from the hotel for our tour through town.

The first stop was at a bookstore, where I not only got another tiny edition of one of my favorite author’s works but also a cycling map of all of Denmark. This would hopefully help us to plan our route and find our way for the next couple of days on our bikes.

Afterwards we decided to visit Det Rundetårn — the Round Tower — Europe’s oldest working observatory, built by King Christian IV between 1637 and 1642, which includes a viewing platform that grants a beautiful view over the old town of Copenhagen — in good weather conditions.
Det Rundetårn is a cylindrical brick building of 34.8 meters height with a spiral path inside. Tsar Peter I the Great actually rode on this path during a visit in 1716, while his wife Katharina followed him in a carriage. The path was constructed wide enough for horse cars to be used on, as the astronomer’s instruments would have been too heavy to be carried up a staircase, and in 1902 the first car drove upon this path to the top of the building.

When King Christian IV started building this tower, then to be known as Regium Stellæburgum Hafniense (Københavns Kongelige Stjerneborg — Copenhagen’s Royal Starcastle), Denmark was — thanks to its astronomer Tycho Brahe — known for its astronomical achievements. Even though Tyco Brahe never used the new observatory, as he had left Denmark after a fallout with the King, his former student Christian Severin Longomontanus ( *1562, †1647 ) delivered the plans for the appliances of the observatory.


Unfortunately the weather was not really inviting us to explore more of the town this afternoon, so we decided to rather take a rest at our hotel to be fit for tomorrows bike ride.
First in the evening we went out again, to find a new place to have dinner at and later, since it had finally stopped raining, to visit Vor Frelsers Kirke — Our Saviors Church — not for religious purpose but for its style.
Unfortunately the church was already closed for visitors, so that we could neither go inside or climb the church’s tower, but at least we were able to have a look and see if the opening hours would fit to our schedule for the next day, which unfortunately they did not.

The church's main building was built by Lambert van Haven in red brickstone in a Dutch baroque style and inaugregated in 1696. The tower was not added to the church until 1752, after a design by Lauritz de Thurah. The upper part of the church’s tower is made of a wooden construction in black oak tree with golden details and an outside staircase, and reaches a height of about 90 meters, which only was possible to reach by using wood, as the ground, on which the church is build, is of sand.


We spent a little while admiring the building before it was time for us to call it a day and make it back to our hotel for the last night in Copenhagen.


You can find more photos from Denmark on my website.




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Friday, February 10, 2017

Calendar Photo of the Month: February 2017

The Hurtigruten's Midnatsol in Svolvær, Austvågøya • Norway



This photo is from my German Lofoten calendar. The story of this day is told here. More photos from Norway and the Lofoten can be found on my website
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Friday, February 3, 2017

The Scandinavian Adventure: Helsingborg - Copenhagen

(Sunday, July 13th 2014)

When we woke up the weather had unfortunately not changed for the better, so our plans for having a sightseeing tour through town before crossing the Öresund and riding our bikes back to Copenhagen got destroyed. Neither of us fancied riding in the rain.
We considered for a little while to take the ferry over the Öresund and making it from Helsingør by train back to Copenhagen, but I was unable to find a route that would not have forced us to change trains at least once.
So instead we decided to see if the Swedish Railway (SJ) would take us and our bikes directly back to Copenhagen as well. I cannot say that I had a lot of hope for this, because the SJ had crossed our plans to go from Narvik by train to Stockholm before. But in this weather it was at least worth trying.
Thankfully on this train it was no problem to get a ticket for both us and our bikes and soon we were back at the same hotel we had just left a day ago to stay for two more nights.

It was sad to know which great areas of Zealand we had missed out on, due to the weather, but neither of us regretted the decision.

First in the early evening the rain stopped, and we went out again for dinner and a short evening walk through Copenhagen.
Our evening walk led us from Nyhavn via Amalienborg, the residence of Queen Margrethe II of Denmark (*1940, ♛ 1972) , along the harbor toward the statue of the Little Mermaid to remember the tale Den lille havfrue by Hans Christian Andersen (*1805, †1875), the famous Danish poet.


Amalienborg Palace is built in the rococo style, which developed from the heavier baroque style when the original castles got crowded and King Louis XV of France chose to stay in city palais rather than his castle of Versaile. The style spread from France to other parts of Europe as well, and the Amalienborg Palace is considered one of the finest examples of Rococo architecture in Europe. Built during the reign of King Frederick V (*1723, ♚ 1746, † 1766) to celebrate the 300th anniversary of the coronation of King Christian I of the house of Oldenborg, and designed by the court’s architect Niels Eigtved (*1701, †1754), who also designed buildings in the surrounding area.
The Palace is constructed on an octagonal site and consists of four equal buildings, which originally were given to the four noblemen A.G. Moltke, Christian Frederik Levetzau, Joachim Brockdorff and Severin Løvenskiold. Already during the building period the Palais for Severin Løvenskiold was sold to the Schack family.
After the royal palace of Christiansborg burned down — during the night of February 26th-27th 1794 — leaving King Christian VII (*1749, ♚ 1766, †1808) without a roof over his head, he acquired the Palaces of Moltke and Schack and turned Amalienborg Palace into the winter residence of the royal family.
Today the Queen resides in the Palais Schack, Palais Moltke is temporarily accessible by the public as a museum, while Palais Levetzau houses the family of Prince Joachim and Princess Marie, when they are in Copenhagen. And the Palais Brockdorff is, since 2010, the residence of the crown prince Frederik and crown princess Mary Elisabeth.

Direction
Original owner
Palais Name
Today's usage
30˚
Joachim Brockdorff
Palais Frederik VIII
Residence of crown prince Frederik and crown princess Mary Elisabeth
150˚
A.G. Moltke
Palais Christian VII
Publicly accessible as a museum
240˚
Severin Løvenskiold / Schack
Palais Christian IX
Queen Margrethe II's residence
330˚
Christian Frederik Levetzau
Palais Christian VIII
Residence of Prince Joachim and Princess Marie


You can find more photos from Denmark on my website.




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Friday, January 27, 2017

Aperture Explained Part 1

Have you ever wondered how to set your aperture in relation to the shutter speed (and ISO) to get a good exposure? Have you ever wondered how you could get those photos where the subject is in focus and the background is not? Have you ever wondered why photos taken with the same aperture but different lenses look different in terms of depth of field? All of this will be explained the following series of articles. There will be some math involved,but don't give up on it just yet because it will all become clear if you stick with me. If you do not have a fancy SLR or mirrorless camera, but a compact camera, the same rules and principles will apply. Instead of changing the aperture you will have to use a different program from your camera's menu, and I will tell you which one. Today we will start with the definition of the Aperture and how to get good exposures. So let's have a look.


The Definition of the Aperture


The aperture is the opening in the lens, which is responsible for part of the exposition, as it decides how much light at a given time can pass through the lens.1 It is defined as the focal length divided through the absolute diameter of the lens.



So the aperture decides how far open the lens is in relation to the focal length you are using, as seen in figure 2.


But the aperture does not only have an influence on the amount of light that can pass through the lens, but on the depth of field. The depth of field means the area in the photo that is sharp while its surroundings are not. So a photo of, say, a blossom, where the blossom is tack sharp and the field that surrounds the flower is out of focus, has a small depth of field.

A landscape photo where basically everything in the photo appears in focus, has a large depth of field.



To get a smaller depth of field, you need to use a wider aperture–which means a smaller aperture value. For a stunning landscape with a large depth of field, you need a narrower aperture–which means a bigger aperture value. And in this very moment you are very confused, because how can a wider aperture mean a narrower aperture value and vice versa?
Remember the definition of the aperture–the first formula I gave you?


The aperture is defined as a fraction. The aperture value, which you see in your camera display, is the denominator of the fraction, while the numerator–the focal length–is 1. So if your camera display shows you an F4, you are in fact using an aperture of F/4; and if you are using F16, you are using F/16. So a lower F-number (4) means a higher F-value and vice versa, because F/4 > F/16. Or simplified: you will get more cake (1/4) if you have to share it with only four people, than if you have to share the same cake with sixteen people (1/16). (More cake = more background blur.)
For a landscape photo, you would want to have as much of the scenery in focus (less background blur) as possible–so you would therefore use a small(er) aperture, while for a photo where the subject is supposed to stand out against its surroundings (more background blur) by being the one thing in focus, you would use a narrow(er) aperture.

If you are using a compact camera for which you cannot change the aperture directly, you can achieve a small depth of field by using the macro mode, usually a menu setting with a flower icon. For a large depth of field you would use the landscape program, usually a setting with a landscape icon, and for a depth of field in between those two you would use the portrait mode.

Why are my aperture values so strange?


If you have a look at the full-stop apertures that your camera offers2, you will soon realize that those values look a little strange. Not only is one stop3 wider than 8 not 7 or 4 but 5.6...one stop narrower than 8 is not 9 or 16 (that's actually two stops) but 11. So let us have a look why that is the case. The explanation lies in the shape of your lens. It is a cylinder, based on stacking circles on top of each other, and not a cube. So the amount of light that can pass through that "aperture-circle" in a very short timeframe–imagine super thin round slices of light–would equal the area of the circle. To calculate the area of that circle, you would use the following formula:


Let us try an example calculation and assume that the radius of the circle is 1, which means the area of the circle would be calculated as:



Now what we would like is to double that area...so let's see how large our radius needs to be for that:



So in order to double the area of a circle you have to multiply the original radius with √2. Now let's see what that means for our aperture-numbers, how do they change if we multiply them with √2.
Starting Aperture Next
smaller aperture (√2)
1 1.4
1.4 2
2 2.8
2.8 4
4 5.6
5.6 8
8 11
11 16
16 22
22 32
Figure 9: Aperture-numbers (full stops)


So now you know where those numbers come from :) In the next article of this series, which will be published here on February 24th 2017, we will have a look into how the aperture, shutter speed and ISO work together in creating the right exposure for your photo.


1 The shutter speed decides how long that opening exists and how long the sensor/film in your camera is exposed to the light. Back to text
2 If you are using a compact camera, you would have to look into your photo's extended file information (exif) to see which aperture is used by which mode. This information is available for all digital cameras and can be viewed with tools like exiftool, or within, for example, the Library module of Adobe Lightroom. Back to text
3 The doubling of the area that allows light to pass through the lens is a change by plus one stop. Bisectioning of the area means a change of minus one stop. Back to text


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Friday, January 20, 2017

The Scandinavian Adventure: Copenhagen - Malmö - Helsingborg

(Saturday, July 12th 2014)



Today we woke up to another day of beautiful weather in Copenhagen, we had already bought our train tickets to get over the Øresundbro (Oresundbridge) to Malmö by train yesterday. So all we needed to do was to get our breakfast and afterwards check out of the hotel to get to the railway station in time for the train. I had plotted a route into my GPS that would take us to the railway station, but only too soon we were surprised by a construction site and were not allowed to follow my plotted plans. Thankfully yesterday’s visit of the town had provided me with a reasonable good map in my mind, so we were able to find our route without too many stops and arrived at the railway station in time for our booked train.
The ride on the train from Copenhagen to Malmö only took 20 minutes, so about an hour after we had left the hotel in Copenhagen we arrived in Sweden.

Even though I had plotted the route from Malmö to Helsingborg into my GPS we still wanted a paper cycling map, as my GPS alone would be no good for a ride through an area I was not familiar with, all that would happen was that we would end somewhere where we weren't supposed to be, or as in Levanger at some closed bicycle path again.
After we had what we needed for the day, we decided to spend some time in Malmö, which I remembered from a previous visit as a neat little town. Unfortunately I was unable to find the places again that I had discovered back in 2003, so our visit was only a very brief one before we decided to hit the road again and start the day’s bicycle tour.
I later learned that we hadn’t been far from what looks like a beautiful park on the map, which probably would have provided me with many opportunities for taking photos. Well, I guess that means that I will one day in the future go back there again.

As so many times before the hardest thing during a bike ride is not the ride itself, but finding the way out of town. But as soon as we had made it out of Malmö, we were able to follow small roads and bicycle paths with very little traffic. Of course, as so often before, what had looked like a beautiful path on the maps soon turned out to end up as a pure sand path, which we could not ride on at all. So we had to turn back and find an alternate route, costing us time and some nerves.
Still as long as the weather would play along with us, it would not be a disaster.
The scenery on this side of the Öresund was not as beautiful as I had anticipated from what I knew about the Danish side. But then we would have the more scenic route still ahead of us for the way back to Copenhagen tomorrow, for which we had planned to take the ferry from Helsingborg and then ride our bikes from Helsingør to Copenhagen…

Those of you who are not familiar with the Scandinavian languages Norwegian, Danish and Swedish, might have started to wonder why I sometimes write the Øresund with an Ø and sometimes with an Ö. While Danish and Norwegian use the letters ø and æ the Swedish equivalents are ö and ä, so depending on which side of the Øresund I am on I adapt its spelling.

When we arrived in Landskrona, we had made it through about half of today’s bike ride of in total 81 kilometers, and we decided to stop and find ourselves a cafe to take a break and have something to eat. Clouds had been moving in and it looked like it might start raining anytime soon, so we finished our break faster than we might would have liked, and got back onto our bikes. Again it took a few detours to make our way out of Landskrona, and find the route again that would lead us to Helsingborg. But once we had found it, it was easy to follow and reasonably well equipped with signs that would lead us through a forest rather than along the European Road nearby.

Unfortunately by the time we reached Helsingborg the weather had turned and, thankfully first after we had checked into our hotel for the night, it started raining. On our way through Helsingborg to find a restaurant for dinner we learned that this town could offer us some great sights in the morning, if the weather was to change for the better until then…


You can find more photos from Denmark on my website.




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Friday, January 13, 2017

Calendar photo of the month: January 2017

Considering tomorrow it will be four years ago that I started the group part of my New Zealand adventure I figured it would only be fair to start this year's calendar photo of the month edition with a photo from New Zealand:



This is from Franz Joseph Glacier on the South Island of New Zealand, which I was able to visit by helicopter.

And for those who have followed my blog or calendar publications over the last few years, yes I have recently changed the layout for the 2017 calendars, to give the photos more room.
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