What is the photo directory?
The photo directory is a collection of portion size images for estimation of food portion size. The images are a mixture of “As served” image series for estimation of the portion size of foods where foods can be served in any amount e.g. rice, pasta and beans and “Guide images” which depict foods which come in pre-determined amounts such as bread rolls, biscuits and crisps. There are also cups and glasses with sliding scales.
As served image
Guide image
The images include the 104 foods from the UK Young Person’s Food Atlas which was developed for use with children aged 18 months to 16 years and their parents. The accuracy of portion size estimation using these images was evaluated in an absolute validation study where children were fed foods in school and asked to estimate the portion size of the amount served and any food leftover1 and further tested in a relative validation against weighed food diaries2.
This directory of images has been added to as Intake24 has been developed and adapted for other populations. Some are images added to the UK version of Intake24 in order to try and improve portion size estimation of specific foods (e.g additional images of different types of chips were added including thin cut, thick cut, French fries and curly fries). A large number of images have been produced and added by teams adapting the system for other countries. Where possible these have followed the guidance on taking new photographs given in the Intake24 toolkit meaning the basic format and viewing angle remain consistent. As the directory includes portion size images which were already in use in various countries as well as photos taken specifically for inclusion in Intake24 there is some variation in both the format and the coding systems employed.
Some of the image collections have undergone validation whereas others have not. Although the accuracy and precision of portion size estimates varies with food morphology, the principle of using the various portion size image formats included in this directory has been extensively tested.
Full details of each image series including; the population with which they are intended to be used, the team producing the images, details of any validation conducted and the weight of food displayed are given in the Excel document “Directory of portion images”
Guidance on use of the directory
Please note - the directory is a work in progress. All of the food names and file locations are entered however work is ongoing to add the additional details.
The directory includes summary data for each image series in the first sheet “Food image collections”. The variables included are:
File location – Folder and sub-folders detailing where the images are located.
Food– The type of food displayed in the image.
Description - Details on how the food is prepared or presented e.g. 7 images of slices of apple in a bowl.
Crockery – Whether the food is displayed on a plate, bowl or tray.
Cutlery – Whether cutlery is included in the image for size reference.Increments – Details of the difference in weight of food displayed in a series where there are multiple images of each food.
Image type – Whether the image is a guide image or part of a series of as served imagesBackground – Whether the images are taken against a white or black backgroundPopulation – The population the images are intended for use with. This could be a locale e.g. India or a population sub-group e.g. children or people with a particular health condition.
Study – The study they were developed for (if appropriate)Validation – Details of any testing of the validity of estimates made using the imagesTeam – The people who developed the food photograph seriesReferences – Links to any publications, tools or websites associated with the food photograph series.
The second sheet in the directory “Individual images and weights” gives details of each individual image in an as Served series and of the individual items in each guide image along with the weight of food displayed. The variables included are:
File location – The file path indicating where the image is stored
Food– The type of food displayed in the image.
Photo code – This is the code given to the individual image for the As served images and the individual item within a guide image.
Weight (g) – Is the weight of the food in grams in the majority of cases. For a small number of foods it is a factor e.g milk on cereal.
Notes – This includes any special instructions on how to use the value in the weight column e.g. milk on cereal is given as a ratio of the milk to cereal rather than a gram weight value.
Note on the photo codes
The photo codes are not consistent in format as they are a combination of images that were designed for use in face-to-face dietary interviews and images developed specifically for use in Intake24 by different study teams. For the guide image the code is generally the image name plus an item number (or letter) however, this is not always the case. Some of the original images published in the Young Person’s Food Atlas are included which have the full code displayed by each item on the image. Where a series spans a number of images such as is the case with chocolate GChoc, Gchoc1 etc the coding gets quite messy as Gchoc01 is on Guide image GChoc2 giving an item code of GChoc201. Some of the later images added to the system were hotspotted so the item can be selected simply by clicking on it and therefore no coding is visible on the image. For these photos the code is either a description of the item or a description of the item’s position e.g. top left.
Glasses sliding scale
This details for each of the glasses in this image series the weight of water the glass contains when full and the weight to fill each glass in 1cm increments.