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Welcome to my blog which contains comments on my sports photographs 

The Mathematics of Depth of Field (DoF)

March 15, 2023  •  Leave a Comment

Depth of Field (DOF)


Depth of field is the distance between two planes, a closer one and a farther one, in which objects  can be positioned to have an "acceptably sharp" image formed in a camera.

There are two formulae for calculating Depth of Field (DOF), a simple one as described below which produces an approximate value and more a more complicated one which produces a more accurate value. The latter is not discussed in this document.


I will focus on the simple formula as below.


           DOF = (2 u2 N c)/f



  • C = circle of confusion*
  • F= focal length
  • U = distance to subject
  • N – F number


*circle of confusion has been defined as the largest blur circle that will be perceived by the human eye as a point when viewed at a distance of 25cm. Note there are more specific definitions but for the purposes of this document the above definition is considered sufficient.

The formula shows that DOF varies proportionally with the aperture, and with the square of the focal length and distance to subject.

Example: what is the DOF of a 50mm lens, when the circle of confusion is 0.029mm, f-stop is f/4 or 4 for the calculation, with a focus distance of 1200mm (1.2m)

Answer: square of u = 1200 * 1200 = 1,440,000

So DOF = 1,440,000*2*4*0.029 = 334,080 divided by square of focal length = 50 *50 = 2500


Ie 334,080/2500 = 133.632mm = 0.13m


An example of Camera "Back Button Focus"

February 16, 2023  •  Leave a Comment


AA1V4356AA1V4356" TULLYORIOR and R A Devine ( 10 , PURPLE; white sleeves; red cap,white star ) Trainer: Catherine Barry , Owner : Catherine Barry"

In late 2020 my Camera Club held a "Show & Tell " session where members had to present 12 photographs taken from the same place.
I entered this sequence of 12 photographs depicting a horse jumping the last fence at the Portrush Point to Point in May 2018, stumbling on landing and as a consequence unseating the rider and throwing him over the its head where he eventually fell to the ground. The rider was uninjured as he can be seen can walking back in front of the spectators to the changing room.
This was a good example of the use of the "Back Button Focus" on my camera whereby the focussing and taking of the photograph are separated and spread across two buttons. The shutter button which usually focuses when pressed half way down and takes the photograph when fully depressed is only used to take the photograph.  A button at the back of the camera is configured to focus the lens. I depressed both buttons for this sequence and followed the horse and rider such that the camera kept the rider in focus throughout. The rider was Rory Devine and the horse was named Tullyoroir.


The full sequence of 12 photographs can be viewed at:


First Event of 2023

February 14, 2023  •  Leave a Comment


1 Limerick Lace (1 ,emerald green and orange hoops ), Jockey - L P Dempsey ,Trainer - G P Cromwell1 Limerick Lace (1 ,emerald green and orange hoops ), Jockey - L P Dempsey ,Trainer - G P CromwellFT8E4411.jpg


First Event if 2023

My first event if 2023 was horse racing at Down Royal. The event was the Molson Coors Raceday national hunt meeting.  It was also Students’ Day and was noisy. There were three hurdle races , three steeplechase races and a flat race to complete the meeting. The meeting was the only one in the UK and Ireland on the day so got good coverage on Racing UK TV. The weather was good considering it was January- dry and bright and not too cold for most if the afternoon. I took photographs with 24-70 and 70-200mm lenses on both sides of course at the the last hurdle and fence as well as some at the finish. I had 5 photographs published in a weekly newspaper. Photographs from the day can be viewed at gallery


A Day at the Races

January 10, 2023  •  Leave a Comment


As of March 2022 I have attended and photographed 270 horse race meetings. I thought it would be interesting to document the things I do for each meeting in terms of pre-meeting, at the meeting and post meeting activities. I have attached a chart detailing these activities.


Event Activities - jpg-2023-01-10_15-36-16Event Activities - jpg-2023-01-10_15-36-16

Top viewed photograph in 2022

January 10, 2023  •  Leave a Comment

Stephen Metcalfe (Leeds City AC) Triple Jump-3rd place 15,03mStephen Metcalfe (Leeds City AC) Triple Jump-3rd place 15,03m

This is the top viewed photograph on my site in 2022. The list is at:

I took it at the GRE Games at the Antrim Forum in Northern Ireland in 1982 and shows Stephen Metcalfe jumping in the long, ship and jump comptetition.


Camera Club Zoom Talk in October 2020

January 08, 2023  •  Leave a Comment

Rory McIlroy after breaking the course record at Royal Portrush in 2005


Rory - IMG_1479Rory - IMG_1479This is the image in question. I took this on 12th July 2005.
It is of Rory McIlroy on the 18th green at Royal Portrush after he had broken the course record for the course. He shot an amazing score of 61.
He was playing in the second day of the five day North of Ireland Amateur Golf Championship. The competition is played each year in July over the Royal Portrush and Valley Courses. The first two days are stroke and the top 64 players enter a match play competition over the last three days with the final on the Friday afternoon. I have attended this competition for many years and watched Darren Clark win it as well as watching Graeme McDowell, Padriag Harrington and Paul McGinley compete when they were amateurs.

I presented this slide set to Larne Camera Club members via Zoom on Tuesday 13th October 2020.
The title of the members talk was " The Impact on my photography of setting up a web site"
I covered my photography pre-web site from 1978 to 2005 and post-web site from 2005 to the present showing photographs that I considered had been successful in my terms and talking about the subjects and the background to taking the photographs in each case.

hmphotographs | 2020-10-08th-Camera Club Slide set V1

Where to Stand?

January 07, 2023  •  Leave a Comment


The photograph below is of the 2010 JNWine Champion Chase at Down Royal and shows Killyglen ridden by Paul Carberry on the left and Kauto Star ridden by Ruby Walsh in the right. Killyglen was owned by David McCammond of Killyglen and trained by Stuart Crawford at Magheramourne near Larne in County Antrim, N Ireland and finished 5th in the race. Kauto Star, winner of the race was trained by Paul Nicholls from England.

Killyglen , Jockey Paul Carberry 5th & Kauto Star , Jockey Ruby Walsh - Winner - T8E4723-e2Killyglen , Jockey Paul Carberry 5th & Kauto Star , Jockey Ruby Walsh - Winner - T8E4723-e2Killyglen
Trainer - S R B Crawford
Owner - D L McCammon


Collection of Photographs of Champion Race at Down Royal referred to below: hmphotographs | 2023-01-06th-Where to Stand?


Ansel Adams states that “A good photograph is knowing where to stand” and best selling author Tom Ang states in one of his books  “The essential foundation for every image you make is your choice of viewpoint”
I agree with these statements and thought it would be interesting to attempt to relate them to my own experience.

At each event I attend the most difficult decision I make is usually where to stand. I have attended the same events on many occasions and struggle with this decision each time.

My most attended event is horse racing at Down Royal. I have attended this race track on 104 occasions ( as at November 2022) and with 7 races at each meeting photographed 728 races so I have focused on this location for the purposes of this discussion.

I will state at the outset that my objectives in taking horse racing sports photographs are to capture action pictures of horses galloping and jumping as well as interesting photographs recording the events such that parties involved with a horse will consider buying a print or jpg file and newspapers editors will consider publishing in the sports section of their newspapers.

In most races at Down Royal the horses and riders pass you two times if you stand in the correct place so you get two bites of the cherry. I usually  photograph from the same place on both circuits but I have moved from the last fence to nearer the finish for the second circuit  to be able to get to the winners closure in time. 

At Down Royal the direction of the light is not usually a problem as the horses run towards the light at the last fence and the finish. Backgrounds are a problem as there are car and bus parks near the last fence and overhead electric power lines and poles near the finish.

Each time I attend Down Royal I to and fro on where to stand for each race. A horse race is an exciting, colourful and dangerous event.

There are a number of viewpoints at Down Royal and it is tempting to try to summarise where I stood for each of the 728 races photographed. I may attempt this analysis in the future however for the purposes of this exercise I have considered one race which I have photographed 12 times. This is the Grade 1 Champion Steeplechase which is held at the two day festival of racing in early November each year.

It is a major National Hunt Race in the UK and Ireland Racing calendar and it attracts the best horses, owners and jockeys as well as the top sports photographers from across Ireland. A National Hunt race means the race includes fences. Where to Stand for Flat races poses different questions than jumps races.

I photograph a horse race at Down Royal from a number of locations  ie parade ring, leaving the parade ring, going down to the start, running on the course, jumping - usually the last fence, running up the finishing straight, crossing the finishing line, entering the winner’s enclosure and in the winners enclosure.

The photographs which cause me most indecision are:

- running up the finishing straight and
 - jumping the last fence.
 - approaching/crossing the finish line.

In each case you can stand on the horses’ left or right side as they run to the finish line.

At the last fence there is also the option of standing on a ladder which can get you above spectators and/or provide more of the horse as it jumps the fence.

I have compiled a collection of photographs from the galleries of the 12 races to demonstrate where I have stood for the various races.  I have also included photographs taken in the parade ring, leaving the parade ring, going to the start and entering the winners enclosure and in the winners enclosure. Where to stand is less of a problem for these photographs because they were mostly staged and arranged or are random shots. Problems arose though if the groups were standing with their backs to the sun and a flash unit was needed in those circumstances.

I have listed below the various races attended by year, winning horse name and in each case which side of the course I photographed the horses jumping the last fence or running up the finishing straight. I have also indicated when I used a ladder at the last fence. The ladder allows the photographer to get above spectators heads and also provides for a fuller view of the horse as it jumps the fence.




Last Fence

Last Fence



Left Side


Right Side

Other Fence



Left side

Right Side






Kauto Star








Quinto De La Rogue








Kauto Stone








Rui Du Mee








Road To Riches








Don Cossack








Valseur Lido
















Road to Respect








The Storyteller
















Envoi Allen
















Factors that affected the decision as to which side to stand:

1 It was easier to get to the winners Enclosure from the left hand side before horses returned to the winners enclosure

2 The location of the last fence also affected whether the last fence was the chosen – the further away the last fence was from the finish line the longer it took to get to the winners enclosure.

3 The location of the last fence also affected the background – some locations on both sides had cars and buses showing

4 In the 2010 Kauto Star Race a fence past the finishing post was chosen which had the Grandstand in the background. It was not possible to get to the last fence for the final circuit so photographs were taken from the run-in near the finish.

5 The last 4 races were photographed from the left side using a ladder primarily because it was possible to get to the winners enclosure in time to photograph the winning representatives. The ladder also improved the background.

6  I have photographed this race from the left hand side of the course on 8 occasions compared to 4 on the right primarily because of the ease of getting to the winner's enclosure on time. 

7 My preference is to photograph from the right hand side of the course as the horses run to the finish as for 2015 Don Cossack and 2016 Valseur Lido. The background is better if the fence is positioned in a certain place at the final fence when the photographs were taken from a kneeling position. On the run-in to the finish it is possible to get the spectators in the photograph which adds to the atmosphere.

8 The photograph shown above of the 2010 Race showing Kauto Star jumping was taken at a fence beyond the finish on the left hand side of the course and is probably my favourite of all photographs taken of the race, mainly because it is of Kauto Star, a very famous race horse but also because the horse on the inside (Killyglen) was a locally owned and trained horse. Also I liked the fence location, the background of the grandstand and the direction of the light. I only shot from this position once because the horses only passed once and it was not possible to get to the last fence on time.





Mountain Runnng Events

October 09, 2022  •  Leave a Comment

Gavin Bland (12) Borrowdale - winner in 1:43:00 - FT8E3138-3Gavin Bland (12) Borrowdale - winner in 1:43:00 - FT8E3138-3

Between 2005 and 2017 I photographed 43 Mountain Running events in Northern Ireland. There were mostly in the Mourne Mountain.

I have over 10,000 photographs in my gallery -

Mountain Running is organised in Northern Ireland by the Northern Ireland Mountain Running Association (NIMRA) and the two Athletics Clubs most involved are based in Newcastle- Newcastle AC and Mourne Runners.

The same races are run every year which provided the opportunity to photograph the races from different locations.

Some of the races I have photographed are as follows:

- British Championships: 2017, 2013, 2012, 2011, 2010, 2009 2008,2007

- Lurig Mountain Race in Cushendall - 2011, 2010, 2008, 2007,2006

- Race over The Glens - 2015, 2014, 2012, 2011, 2010, 2008, 2007

- Sevens Sevens in The Mourne Mountains - 2010, 2009, 2007

- P&O Irish Sea International Mountain Race at Knockdhu - 2006

- World Police and Fire Games including the Mountain Race in the Mourne Mountains - 










Horse Race Meetings attended

May 19, 2022  •  Leave a Comment

I have over 50,000 photographs loaded in my Horse Racing galleries on my site and so I though I would count the number of meetings I have attended over the years.

As of March 2022 I have attended 270 meetings which equates to photographing 1,754 races - a track meeting normally has 7 races and a Point to Point meeting has normally 6 races - though sometimes if there are two many entries in a race it is divided into what is called into a Division 1 and a Division 2 race. I was once at an East Antrim Hunt Point to Point Meeting at Loughanmore, near Templepatrick where 11 races were run.

I have attached a spreadsheet showing the horse racing venues I have attended.


Number of photographs in each Gallery by Location       
Location/Meeting Number of Meetings Attended Number of photographs Date
Punchestown 4 2361 2015, 2016, 2017, 2018
The Curragh 1 608 2015
Royal Windsor 1 344 2015
Leopardstown 2 1269 2014, 2015
Ascot 1 104 2012
Laytown 3 795 2011, 2013, 2014
Down Royal 98 23753 From 2010
Downpatrick 60 12943 From 2010
East Antrim Hunt at Loughanmore 18 4673 From 2010
Mid-Antrim Hunt at Moneyglass 13 3234 From 2010
East Down at Tyrella 15 3905 From 2010
Iveagh at Moira 8 1955 From 2010
Crumlin 6 1126 From 2010
Fermanagh at Necarne 6 2268 From 2010
County Down at Loughbrickland 4 1054 From 2010
North Down at Kirkistown 13 2037 From 2010
County Down at Loughanmore 1 252 From 2010
Newry 3 584 From 2010
Route/Portrush 7 1752 From 2010
Tynan at Armagh 5 771 From 2010
East Antrim Hunt at Lisnalinchy 1 49 1982
Total 270 65837  


My Web Site Configuration

May 19, 2022  •  Leave a Comment

Zen forst page  v2 - 2022-05-17_20-32-21Zen forst page v2 - 2022-05-17_20-32-21 There are many ways to configure a web site.

I set up my first sports photography web site in 2006 and have been using Zenfolio since 2010.

IN early 2010 I decided to set up Zenfolio by type of sport ie all photographs for a particular sport in a collection of galleries eg Cross Country Running, Mountina Racing, INdooor Athletice etc.

I created a gallery for each event I attended.

When you enter my site you will be presented with galleries for each sport eg Horse Racing, Golf, Mountain Running, motor Cycle Racing, Sailing, Rugby, International Cross Country, indoor Ayhletics, Hockey, General Sports and some other ad- hoc galleries.

If you select Horse Racing you will be presented with the Horse Racing tracks I have attended and within each of the tracks I have grouped the photographs by meetings in each year.

In Zenfolio photographs are uploaded into Galleries. Galleries can be combined into Groups of Galleries to many levels. Zenfolio also has a Collection facility which contains a pointer to selected photographs in their Galleries. This means that the original photograph is only stored once in the system.

In order to allow the viewer an alternative way into the galleries of photographs I have created an index by year from “2005 and earlier” up to the “current year”. Within each year I have listed each event attended with a pointer to the gallery containing the photographs of the event. 

Zenfolio also has a blog facility and I have included items which interest me mostly related to the events I have attended. 

Zenfolio gas a “Customs Page “ facility which I have used to create an index to my blog which shows a heading for the log entry and a pointer to the blog details.

Zenfolio has many different front page styles and format for displaying sites. I have selected a basic format where I have selected a number of featured galleries followed folllowed by Galleries recently posted with finally the galleries in my site.



Changes at Down Royal in 2018.

May 17, 2022  •  Leave a Comment

Kauto Star , Jockey Ruby Walsh - Winner followed by Sizing Europe , Jockey A E Lynch 2nd - CU2D1114-e2Kauto Star , Jockey Ruby Walsh - Winner followed by Sizing Europe , Jockey A E Lynch 2nd - CU2D1114-e2 The picture above shows Kauto Star and Ruby Walsh winning the JNWine Champion Chase at Down Royal in 2010.


The last meeting at Down Royal Racecourse , arranged by the Down Royal Corporation of Horse Breeders was held on on Boxing Day 2018. The Corporation had run race meeting for 35 years at the course but the lease was not renewed by owner of the Course Mike Roden of Dublin based Merrion Property Group who purchased the site in 2005.

Racing has continued at the Course organised by new owners Merrion Group. 

I have taken photographs at the site since 2010 and thought it be appropriate to create some collections of photographs under different headings of photographs I have taken at the course.

The first collection shows the winners of the Champion Chase, a Grade 1 Steeplechase held in November each year, followed by some Ulster Derby winners, Down Royal staff, Spectators, Familiar faces, Best Dressed and members of the press.

The photographs can be viewed at:



Show and Tell - "I know what you did last autumn"

January 18, 2022  •  Leave a Comment

My Camera Club held a Show and Tell on Tuesday 11th January 2022. The subject was show and tell up to 6 photographs on the topic "I know what you did last autumn".

I submitted 6 photographs as shown at the attached link taken at the second day of the two day race meeting at Down Royal on Friday  29th and Saturday 30th October 2022 -

This is a significant racing weekend in Irish Racing with total prize money ofer the two days of 405,500 Euro - 144,500 Euros on Friday and 261,000 Euros on Saturday. 


Pic5-HArryMarcus-Pic5-HArryMarcus-"01st Frodon??and Bryony Frost ( 2 , blue, white chevron ) Trainer - P F Nicholls , Owner - P J Vogt" yal on Friday

The Golden Rectangle

January 09, 2022  •  Leave a Comment

Picture 1Picture 1This rectangle represents a Golden Rectangle where the width is 16.28 units and the height is 10 units - the ratio of the width to the height equals the Golden Ratio which is 1.618
Note the vertical line in the middle of the rectangle creates a square of 10 unit sides and a vertical rectangle on the right which is 10 units high by 6.18 units wide- the ratio of the the sides is 10/6.18 = 1.618 - the Golden Ratio.

The Golden Rectangle (See pictures at: }


The Golden Rectangle is a rectangle where the dimensions adhere to the Golden Ratio ie the ratio of the width and height is 1.618.


For example if the height is say 10” then the width will be 16.18” (10 times the Golden Ratio of 1.618)


Interestingly the Golden Rectangle can be split into a square with a vertical rectangle at the end (Picture 1). This vertical rectangle also has the dimensions of a Golden Rectangle which can be split into a square and rectangle at the top or bottom and again the new rectangle is a Golden Rectangle and so on. This is the basis of the Golden Spiral.


Back to the original rectangle (Picture 1 ) discussed and the square and vertical rectangle at the end. The vertical rectangle if rotated 90 degrees anti-clockwise fits into the bottom left of the square (Picture 2). It will also fit the bottom right part of the square drawn for the right of the overall rectangle (Picture 3 ). This also applies to the mirror image of the original rectangle where the square is at the right side of the rectangle (Picture  4).


The end result is a Noughts and Crosses shape which is similar to the Rule of Thirds shape with the four focal points (Picture 4 ).  Note in Picture 5 the Golden Rectangle is represented in Blue and the Rule of Thirds in Green


I have seen it said that the Rule of Thirds is based on the Golden Rectangle and that the Golden Rectangle focal points are more effective from an atheistic point of view than those in the Rule of Thirds.


The other interesting feature of the Golden Rectangle is the closeness of the shape (1.618 ratio) to the 35mm wide film ratio ( 36mm by 24mm = 1.50 ratio) and the modern full frame camera sensor ( 36mm by 24mm = 1.5 ratio)


There are many architects, artists and photographers who have made use of the Golden Rectangle in their work.


The Golden Ratio

January 07, 2022  •  Leave a Comment

IMG_0001IMG_0001 IMG_0002IMG_0002

The mathematics of the F-stop numbers

December 10, 2021  •  Leave a Comment

 Have you ever wondered where the camera f-stop range of numbers comes from ie 1.4, 2, 2.8,4,5.6,8,11,16.

Well it is fairly simple.

The number sequence is related to the area of a circle and the fact that the difference between 2 full f-stops doubles or halves the amount of light that gets through the aperature ie the area of the circle doubles or halves. 

It turns out that if you multiply the preceding number by the square root of 2 ie 1.414 (to three decimal places) you get the next number in the sequence ie 1.4 multiplied by 1.414 = 1.9796 or rounded up =2 or  2 multiplied by 1.414= 2.828.or 2.8 rounded to one decimal place.

It is also interesting that the number either side of a number is either double of half ie 2 and 4, or 16 and 8

I have written out the mathematics explaining the relationship between the numbers and where the square root of 2 comes from.


F stop mathematics 001F stop mathematics 001