Research Article The Effect of Bit Depth on High-Temperature Digital Image Correlation Measurements Steven R. Jarrett, 1 Thinh Q. Thai, 2 Lindsey J. Rowley, 1 Weston D. Craig, 1 and Ryan B. Berke 1 1 Utah State University, Mechanical and Aerospace Engineering, 4130 Old Main Hill, Logan, UT 84322, USA 2 Van Lang University, Faculty of Mechanical-Electrical, and Computer Engineering, 69/68 Dang Thuy Tram Street, Ward 13, Binh Thanh District, Ho Chi Minh City, Vietnam Correspondence should be addressed to Ryan B. Berke; ryan.berke@usu.edu Received 31 March 2022; Accepted 3 May 2022; Published 2 June 2022 Academic Editor: Carlos Marques Copyright © 2022 Steven R. Jarrett et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Digital Image Correlation (DIC) is a camera-based method of measuring displacement and strain. High-temperature DIC is challenging due to light emitted from the sample which can saturate the image. This effect can be mitigated using optical bandpass filters, but the maximum sample temperature range of DIC remains dependent on the camera and camera settings. Among camera settings, bit depth, also referred to as color depth or number of bits, has received insufficient attention in high-temperature DIC literature. In this work, the effect of bit depth on DIC measurements is investigated both analytically and experimentally. It is shown that if image noise is sufficiently low, then increasing bit depth reduces DIC random error. A new metric, the effective number of bits, is presented to determine the appropriate number of bits for DIC images. Using increased bit depth, reduced exposure time, and low-noise images, the maximum sample temperature for DIC measurements was shown to increase without negatively impacting random error. 1. Introduction Digital Image Correlation (DIC) is a camera-based method of measuring displacement and strain. Since its first practical application in the 1980s [1], popularity of the technique in peer-reviewed literature has grown exponentially while other popular strain-measurement methods have not seen a signif- icant increase in use [2]. One area of current research is in increasing the range of sample temperatures for which DIC can be used. The purpose of this work is to explore the effect of a camera’s bit depth, also referred to as color depth or number of bits, on the resulting DIC measurement in an effort to increase this range of temperatures. Performing DIC on high-temperature samples can be challenging due to light emitted from the sample according to Planck’s law [3]. Because images of the sample include both reflected and emitted light, then as sample temperature and emitted light increase, the image brightens until eventu- ally there is saturation of the camera sensor. At relatively low temperatures, this is not a problem because emitted light is not a significant portion of the light collected by the sensor. In situations where the amount of emitted light is significant and sample temperature may change over the course of the experiment, the user must be careful to select a correlation function which corrects for this type of change in lighting [4]. As early as 1996, Lyons et al. demonstrated DIC to be capable of measuring samples at temperatures up to 650 ° C [5]. Because the emitted light is known to be brighter at longer wavelengths [6], one solution to the background radiation problem is to use a blue (~450 nm) light source and bandpass optical filter. In 2009, Grant et al. showed that using blue-light illumination and optical filtering could extend the maximum temperature of DIC measurements to at least 1000 ° C [7]. Two years later, this was extended to 1500 ° C by Novak and Zok [8] and has been used in several other high-temperature experiments [9–15]. Most recently, the temperature limit of blue-DIC has been extended to Hindawi Journal of Sensors Volume 2022, Article ID 6554128, 19 pages https://doi.org/10.1155/2022/6554128