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Refectance Transormation Imaging This document is intended to help you locate all of the equipment and software

which you will need to make your own RTIs. Before we begin looking at the

practicalities I will briey re-introduce the technique and describe how it works.

RTI stands for Reectance Transformation Imaging and describes a set of 

techniques which use ‘multi-light photography to produce interacti!e

representations of a sub"ect. #e make an RTI by taking between $%-&% identical

photographs. #ithin each photograph we light the sub"ect from a di'erent

direction. By combing these photographs (using software called RTI builder) weare able to make interacti!e !isualisations which allow users to mo!e the light

and change the surface appearance. This can be useful in a range of 

archaeological*heritage scenarios including reading gra!estones+ in!estigation of 

gra,ti and imaging documents.

Project Website ou can check for more information on the pro"ect that we ha!e been working on

with churches across the /. http0**ourti.org* 

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Contact Details1areth Beale

Research 2ellow

3entre for 4igital 5eritage

ni!ersity of ork

6icole Beale

Research 7ssociate

4epartment of 7rchaeology

ni!ersity of orkgareth.beale8york.ac.uk

8cdhyork 9 8gcbeale

http0**www.york.ac.uk*digital-heritage

nicole.beale8york.ac.uk

8nicoleebeale

http0**theculturalheritageweb.wordpres

s.com*

Left: St. Peter inscription in porch entrance of St. Andrew’s Church,

Holcombe. Top is a photograph bottom specularl! enhanced "T#. "ight: An

"T# Capture in action at St. $inifred’s Church in %ranscombe. Photograph b!

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RTI Equipment The basic equipment which you will need to make an RTI0

• 7 camera (with the ability to manually focus and manually ad"ust e:posuresettings)

• 7 remote to ;re the camera (alternati!ely+ you can ;re your camera from a

laptop+ connecting it with a cable and using software pro!ided with your

camera+ or this free !ersion0 http0**digicamcontrol.com*  for #indows)• 7 tripod - for the camera

• 7 black*red*sil!er shiny ball < the key is that this is spherical and reecti!e

• 7 powerful light with a nice e!en beam i.e. no rings or imperfections in the

beam.

2rom this basic set you can start to build a more comple: RTI kit. The two areas

where you can impro!e the setup abo!e are0

1) Elevating te !all" ou will need to support the ball somehow unless you

are able to lay it on the oor ne:t to the ob"ect you are recording. #e use a

tripod which has been adapted to hold a ball on a metal rod. 7 studio umbrella

clamp (=&-=>?) is screwed onto a tripod+ this holds a piece of threaded bar which

is then attached to a ball. ou will need to make sure that the ball can be

screwed onto a threaded bar. This can be done by gluing an @A nut to its surface

or by cutting a thread into the ball.

#) Te $igt" #hile you can get away with a torch+ it is useful to get a ashgunas this will make your setup more !ersatile. It will mean that you can use it in

any light conditions as they tend to be !ery bright compared to other portable

lights. ou will also need a way to connect the ash to the camera. ou can use a

physical cable but we recommend using a wireless ash trigger set which allows

you to mo!e the ash as much as you like without pulling on the camera.

RTI %ot&are7ll software needed to process and !iew RTI ;les can be downloaded from

3ultural 5eritage Imaging an organisation dedicated to pro!iding training andaccess to RTI technology. Cn their website you will also ;nd comprehensi!e

guidance and a lot of good e:amples. ou will need two softwares RTIBuilder to

make your RTIs and RTIDiewer to see the ;nished results.

RTIBuilder software0

http0**culturalheritageimaging.org*#hatE#eEC'er*4ownloads*Frocess*inde:.html

RTIDiewer software0

http0**culturalheritageimaging.org*#hatE#eEC'er*4ownloads*Diew*inde:.html  

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'ore $igt $ess $igt

##(*+(,111,

1-1... 1-+.. 1-#+. 1-1#+ 1-,. 1-/. 1-1+

'ore $igt $ess $igt

7perture

Ghutter Gpeed

 ou will also need to download 5ewlett Fackards FT@2itter software+ in order for

some of the functionality in RTIBuilder to work. 1et it here0

http0**www.hpl.hp.com*research*ptm*downloads*download.html

 ou will need to check that your machine has Ha!a (the programming language

that the software is written in) that is !ersion A or higher. 3heck here0http0**www."a!a.com*en*download*manual."sp  

RTI 0uiesRe-reading the British @emorial Fro"ects Introduction to RTI0

http0**ourti.org*RTI1uide

5istoric nglands @ulti-light Imaging for 5eritage 7pplications 1uide0

https0**www.historicengland.org.uk*images-books*publications*multi-light-

imaging-heritage-applications* 

3ultural 5eritage Imagings RTIBuilder 1uide0http0**culturalheritageimaging.org*#hatE#eEC'er*4ownloads*rtibuilder*RTIEhltEFr

ocessingE1uideE!>JEbeta.pdf  

RTI Capture To capture an RTI with the minimum fuss you "ust need to follow these steps0

>) Get up the camera in front of*looking down at the ob"ect to be captured. Get

the camera to manual.

$) @ake sure that the ball is in shot

K) 7d"ust the camera settings to e:clude the ma"ority of ambient light (e.g.

sunlight). ou can do this by ad"usting the shutter speed or ad"usting the

aperture. Ghutter speed is measured in fractions of a second. The faster your

shutter speed is the darker the image will be (see ;gure below). The aperture is

the hole through which light passes in order to enter the camera. The smaller the

aperture is the darker the image will be (see ;gure below).

J) Take a photo and check that it is dark

?) Take a photo with your light on (ash or torch or whate!er you decide to use)

and make sure that the image is nicely e:posed.

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A) Take more photos ($%-&%) with the light in di'erent positions. Ideally you want

to create a dome of lights o!er the ob"ect+ as such the light should be at

appro:imately the same distance from the ob"ect in each shot.

&) Frocess the data using RTIBuilder. The resultant ;le+ with the e:tension .ptm+

is completely standalone. ou do not need to keep the photographs that you tookin stage A)+ but may wish to do so as they are also useful records.

L) Diew and manipulate your .ptm using RTIDiewer.