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 Derek Smith 13 April 2025
Dave Turner, and I attended the LPA Fosters Challenge at Nettleham. The judge for the competition was Sue Wilson from Clay Cross. Axholme took first place with 19 points, Grimsby 2nd, and Cleethorpes 3rd. Louth was awarded 13 points, consisting of: Damselflies Mating – Graham Harrison 4pt Saltwick Bay – Tony Gaskins 4pt The Thinker – Keith Rossington 3pt Muted Swan – Harry Kerman 1pt Pier Number 9 – Dave Turner 1pt It was an interesting competition with some amazing images, a big thank you to Dave Turner for selecting the prints and submitting our entry into the competition.
by Graham Harrison 13 April 2025
Good Morning All Last week at the club member Chris Birchmore took us back in time with old photographs and a very interesting talk on one of Louth's old shops Platts stores. Platts stayed traditional for many years but as like most of the old shops eventually disappeared along with it's upside down sign. There is a blog on our website as well to look at. This week, Wednesday 16th April, we will hold our Print competition with the categories of "Curves" and "Open" to be judged by Diane Seddon of Cleethorpes. Harry is also now taking entries for the local PDI competition, with the categories of "Local Events" and "Open". Regards Graham
by Derek Smith 10 April 2025
Our member Chris Birchmore gave an illustrated talk last night titled "The Shopkeeper and his Assistant". Chris related details of his family origins, and family history in Louth, in particular his connection with Platts Provision Store in Eastgate. It was a very interesting talk which evoked many memories with those members who had themselves been raised in Louth. Many thanks Chris, the preparation, and talk was excellent.
by Graham Harrison 6 April 2025
Good Morning All With all this warm weather some insects are out and about to photograph, I took this photograph in our garden with a Sigma 105mm lens to get close in on the bee. It is another month now, so you need to think about your "Prime Time" project, if you are taking part. Last week at the club Brian McCarthy FRPS showed us his personal journey in photography, Brian takes most of his photographs in his shed building models with lighting and creating photographs that most of us would never think of. This week, Wednesday 9th April, our member Chris Birchmore who will be presenting a historical talk entitled "The Shopkeeper and His Assistant" specifically talking about a relatives memories of working for Mr. Platt the Shopkeeper. For those who have prints for the next competition, with the categories of "Curves and Open", you need to send Dave Turner a list of your entries and bring the prints in this week. Regards Graham
by Graham Harrison 30 March 2025
Good morning, All Last week we held our spring committee meeting, we discussed many topics including the new program which will be available to you all soon and did some preparation for the AGM. This week, Wednesday 2nd April, Brian McCarthy FRPS will be coming along to show us some more of his work. Brian is an ex-member of our club but has more recently been a member of Grimsby Photographic Society. You can also now start sending your print titles for the Curves and Open competition to Dave Turner. Regards Graham
by Derek Smith 27 March 2025
This year’s project is “Prime Time”, simply one photo taken each month with the same prime lens. The resulting 12 images will be shown to members on our “Project Night” next January. Why a prime lens? Well, a lens with a single focal length, a prime lens, provides a photographer with creative options. Composition of the image when using a lens such as this is essential, a photographer must choose a subject and move around that subject to obtain the photo. Every photographer should have a prime lens in their bag, and it doesn't need to be expensive. I recently switched from Fuji cameras to the Olympus / OM Systems camera ecosystem. Now, I use the OM Systems OM-1 camera with two zoom lenses and three f/1.8 prime lenses. For the “Prime Time” project, I'll creatively use the Olympus 45mm (90mm full-frame equivalent) f/1.8 lens, this lens is typically employed for portraits. This tiny, sharp lens, which captures beautiful portraits, was bought used for £149 from a reputable dealer.
by Graham Harrison 23 March 2025
Good Morning All Last week at the club we held our PDI competition for March, with the categories of "Including the Moon" and "Open" judged by Mike Bennett. It was a very good night with some excellent photographs entered in the competitions, especially the Open. There were three twenty points awarded out of twenty photographs in each subject, Tony Gaskins had a very good night winning both the subject and the Open. All the results are on our website under competitions. The NEMPF PDI Inter - club competition went ahead recently, not so many clubs entered this year, I think there were only three LPA clubs who had entered, Louth came 11th, I'll leave it there. Thank you to Harry for organising our entry. This week, Wednesday 26th March it is a committee meeting for committee members only to attend. To keep you busy though you could prepare your prints for the next print competition, with the categories of "Curves" and "Open". Regards Graham
by Derek Smith 20 March 2025
At our meeting last night we held our Projected Digital Image (PDI) competition with the categories of "Including the Moon", and "Open". The judge for the evening was Mike Bennett. Mike skillfully judged the 33 submitted entries in the "Open" category, providing excellent feedback on the various images. After the break Mike appraised the 18 images in the "Including the Moon" category, this had been a difficult subject for members to photograph, and was also challenging for the judge. Congratulations to Tony Gaskins for his first placements with "Moonbell, Mablethorpe" in the "Including the Moon" category, and "Dawn, Whitby" in the "Open" category. As is usual, the Competition page of the website has been updated with the top three placements in each category, and full results. Many thanks to Mike Bennett for judging the competition, and Dave Mann for providing the refreshments.
by Derek Smith 18 March 2025
This morning I took my used OM Systems OM-1 camera, and the used Olympus M.Zuiko Digital 75-300mm, f/4.8 -f/6.7 lens, recently purchased for £249, with me for a photographic walk around the nature reserve at Gibraltar Point. The weather was excellent, and I'm pleased with the resulting images of the various birds to be seen. I believe the bird reflected drinking from the pool is a Common Chaffinch, and the other bird perched on a log appears to be a Dunnock.
by Derek Smith 17 March 2025
One of our members, Richard Hildred is holding an Exhibition, and workshops in Fydell House, Boston, Lincolnshire. See attached posters for further details.
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