Blog Post

Back to Basics

Derek Smith • 10 July 2020
Back to Basics

Recently someone I know bought a new camera, and of course they had many questions, I had to research these to find the right answers, and the first question was:

What is Lens Focal Length?

Focal length, usually represented in millimeters (mm), is the basic description of a photographic lens. It is not a measurement of the actual length of a lens, but a calculation of an optical distance from the point where light rays converge to form a sharp image of an object to the digital sensor or 35mm film at the focal plane in the camera. The focal length of a lens is determined when the lens is focused at infinity.

Lens focal length also tells us the angle of view—how much of the scene will be captured—and the magnification—how large individual elements will be. The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.

As an example use a short focal length 24mm (16mm* or 12mm**)  to capture the interior of a room, or a landscape view.

* = APS-C crop sensor camera    ** = Micro Four Thirds crop sensor camera

What is Aperture in Photography?

Aperture refers to the opening of a lens's diaphragm through which light passes. It is calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16. Lower f/stops give more exposure because they represent the larger apertures, while the higher f/stops give less exposure because they represent smaller apertures. This may seem a little contradictory at first but will become clearer as you take pictures at varying f/stops. Be sure to check your manual first to learn how to set Aperture Priority for your camera, then try experimenting to get comfortable with changing the aperture and recognising the effects different apertures will have on the end-result image.

Selecting a wide aperture of f/2 would ensure that only a small portion of the image would be sharp, whereas a narrower aperture of f/10 would ensure that a greater part of the image would be in focus.

What is ISO in Photography?

In digital cameras ISO measures the sensitivity of the image sensor, the lower the number the less sensitive your camera is to light and the lower the noise in the image.

Higher ISO  numbers mean your sensor becomes more sensitive to light which allows you to use your camera in low light situations, the trade-off of doing so is more noise in the final image.

An example of a situation you might want to choose a higher ISO would be photographing an indoor sporting event where the light is low and your subject is moving fast. By choosing a higher ISO you can use a faster shutter speed to freeze the movement.

What is exposure in photography?

The light meter in a digital camera calculates the correct exposure of the image based on 3 parameters: ISO, shutter speed, and aperture. This is known as the "exposure triangle". Creatively the photographer chooses 1 or 2 of these parameters based upon the subject. As an example when photographing a moving subject you may select a shutter speed of 1/500 to "freeze" the action, ensuring the the subject is sharp. In the case of a portrait in the front of a distracting background the photographer  might select an aperture of f/2 to isolate the subject from the background. The choice of ISO again is an artistic choice, the photographer may choose to set the ISO to "Auto" if the light is variable, alternatively in the case of the portrait set the ISO to the base level of 100 or 200, to give a noise free image.

In the case of the portrait of Kaya, I used a lens with focal length of 90mm (60*, 45**) our location was in shadow under a railway bridge, I set the aperture to f/1.8, and set the ISO to 400. I was using "Aperture Priority" as the camera mode, with the ISO, and aperture fixed the camera calculated the correct shutter speed of 1/200 to give the correct exposure.

The photo of the Hypericum flower was captured with a 120mm macro lens (80*, 60**) ISO 800, aperture f/4, and a shutter speed of 1/60 calculated by the camera.

For further reading on the exposure triangle I found this website to be useful:

https://photographylife.com/what-is-exposure-triangle  

Louth Photographic Society

by Graham Harrison 19 January 2025
Good Morning All There has been a lot of cold foggy weather lately, not to be put off I have been out walking around Binbrook taking a few winter Photos. Last week at the club we were treated to some excellent photography in our monthly PDI competition, in particular the Open competition was of such a high standard our judge Steve Chapman held back nineteen of the photographs out of twenty-four. All the results are on our website. This week, Wednesday 22nd January, those of us who took part in last years project, "Numbers", it is your chance to show us how you interpreted the subject and show your final twelve photographs, which should be one from each month. It is also a good time to start this years project, "Prime Time", one photograph a month taken with the same prime lens. If you don't have a prime lens, use a zoom set to the same focal length for each photograph. Richard Hildred also asked us to send him a few monochrome photographs that he can use in his demonstration in a few weeks' time. You can send them to myself or Derek if you don't have Richard's email. Regards Graham
by Derek Smith 16 January 2025
This was the Society's first meeting after the Christmas break, and it had a good attendance for the first competition of the New Year. The PDI competition, was judged by Steve Chapman, it was his first visit as a judge to the club. The competition had two categories: “Shadows” and “Open”. Steve judged the “Shadows” category first, where members showed great creativity. Entries included tree shadows on buildings, monochrome shadows of people, benches casting long shadows at Whitby, and Dave Turner's winning image of a man's shadow on a wet pavement. After the break, Steve judged the “Open” category. The high-quality images from various genres made judging challenging. He shortlisted 19 entries and then awarded points to choose the top three placements. Tony Gaskins entry of a dawn seascape at Mablethorpe was placed first in this category. The evening competition featured numerous high standard entries, and Steve Chapman, as judge, provided insight, knowledge, and a well-considered critique. The full results, and top three images in each category can be viewed on our website Competition page. Thanks to our judge Steve Chapman, Dave Mann for refreshments, and Paul Rudd on finances.
by Graham Harrison 12 January 2025
Good Morning All I have been out and about working and have seen quite a lot of flooding out at Brandy Wharf and frost at Linwood warren. We start back at the club this Wednesday 15th, after our Christmas break. We start with a PDI competition, with the categories of "shadows" and "open" to be judged by Steve Chapman. The following week is project night when you can show what you did for last year's project which was numbers. Regards Graham
by Derek Smith 8 January 2025
How has your photographic life been this year? I’ve been out taking photographs, but mainly for my own pleasure, and enjoyment. The weather at the start of the year seems to have been wetter, and cooler, warming up later, and this weather pattern has influenced the photos for wildlife. Our club outings to wildlife reserves produced little in the way of insects. My photographic genre of choice is for model photography, and I’ve chosen to work more in studios this year producing a good, but not exceptional body of work. Equipment wise, I’ve stayed with my Fuji camera system, and the various lenses. My only change was swapping the Fuji XF 50mm f/2 lens for the TT Artisan 56mm f/1.8 lens, and the main reason for this was the Fuji lens has a lightly damped, although clicked, aperture ring, and I kept jogging the aperture ring during shooting. I’m certainly enjoying the TT Artisans lens; the slightly longer focal length produces a nicely blurred background, and I intend to use it for more subjects than just as a pure portrait lens. Highlights of the year, well definitely the holiday to Menorca, the nature reserve on the island was literally “alive” with insects and wildlife in stark contrast to the UK. The Empsay and Bolton heritage steam railway, near Skipton, was another delight. Staying for 2 nights at the Cow and Calf Inn on Ilkley Moor, enabled me to photograph the sunset, and sunrise over the moor. In 2025 I want to take more landscape, and creative images, reducing my bias toward portraiture photography.
by Graham Harrison 5 January 2025
Good Morning All I hope you all had a good new year. Thinking I might take a nice winter scene photo this morning, but just a bit of wet snow and rain. We start back at the club a week on Wednesday (15th) with a PDI competition, Shadows and Open, I f you can send your entries to Harry by midnight next Wednesday please. Regards Graham
by Derek Smith 2 January 2025
Hopefully everyone has had a good Christmas, and perhaps enjoyed partying into the New Year. We'll soon be back to normal at the club on Wednesday 15th January, when we hold our first competition of the year, a PDI, with the categories of "Shadows", and "Open". Travelling into Lincoln today, taking advantage of the sunshine, I had my Fuji X-S20 camera with me and the 56mm f/1.8 TT Artisans prime lens, (85mm full frame equivalent), walking around with this small lightweight combination, enjoying taking various photos. Indoors now, and looking at the images, my decision is made, I shall be using the 56mm lens for the "Prime Time" annual project, a fixed focal length prime lens challenges the photographers creative compositional skills. The TT Artisans lens was inexpensive at £160, and produces great image quality, as can be seen from some of these images.
by Graham Harrison 29 December 2024
Good Morning All I hope you have all had a good Christmas. I tried to find one image to sum the year up and came up with this one taken at Whitby, overcast and rain. Not much to report, just to remind you to prepare your PDI's for the next competition on January 15th, with the categories of "Shadows" and "Open", and send them to Harry when as soon as you're ready. The new project will be starting soon as well, one photograph a month using the same prime lens for all photographs. If you only have zoom lenses just set it to the same focal length each time. Regards Graham
by Derek Smith 28 December 2024
The 2024 project was “Numbers”, one photo that included a number for each month of the year, I have just finished my last photo for this month, it has been an interesting project. Our 2025 project is “Prime Time”, one photo each month taken with the same prime lens, (a lens with a fixed focal length). Yesterday I was out visiting the Alice in Wonderland experience at Castle Howard, Yorkshire, I took one camera, the Fuji X-S20, with a Sigma 30mm f/1.4 prime lens to capture some images. Having a fixed focal length certainly makes a photographer concentrate on composition but consider that many iconic photographs from the 20th century were taken in this fashion. My 30mm lens on an APS-C camera is the equivalent of 45mm on a full frame camera, the lens is considered a “normal” focal length. For this project I would probably use my wide-angle Samyang 12mm f/2, (18mm full frame) which I normally use for architecture, or landscape photography, I could also use the TT Artisans 56mm f/1.8 (85mm full frame) portrait lens, either lens would challenge my photographic skills, and I will choose in the next week or so. Photographs taken at Castle Howard with a Sigma 30mm prime lens.
by Graham Harrison 23 December 2024
Good Morning All Last Wednesday we held our annual Buffet and quiz night including Harry's raffle. I think you would all agree we had a very good night, and I must thank all our members for donating so many raffle prizes. Thank you also to my partner Jane for preparing the buffet, Dave Mann for sorting the buffet out and making the drinks and Harry who ran the raffle and read out the quiz prepared by Paul Malley. Thank you Paul for compiling the quiz for us. We now have our Christmas break and when we return on January 15th we start with the monthly PDI competition, Shadows and Open. You can send your entries to Harry after the new year to give Harry a break, it will give us something to do over the festive season. Have a great Christmas. Regards Graham
by Derek Smith 20 December 2024
This was the last meeting of the year, and we celebrated the evening with a delicious buffet provided by Graham's partner Jane, and there was plenty of food for members attending the evening, with some members taking leftovers home. Paul Malley was unfortunately unable to attend owing to ill health, but, he had prepared a general knowledge quiz, with some very obscure questions, which kept us puzzled, and entertained, Tony Gaskins scored the most points, and took the prize cup. Members had brought in items for the raffle, Harry Kerman sold the tickets, and the raffle raised £47 for club funds. Overall it was a very successful evening. So, a big thank you to Jane for the buffet, Paul for the quiz, Harry for running the raffle, and Dave Mann for laying the buffet out, and preparing refreshments. A date for your 2025 diary: Saturday 22nd February there will be an opportunity to photograph a Taekwondo event; details to follow. Wishing all our readers, and members a very Happy Christmas.
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