Response of Manders' and RWC co-localization algorithms in the presence of noise. The sensitivity of various co-localization algorithms to varying levels of correlation and co-occurrence is tested in the presence of noise (SD = 10). The same sets of synthetic data as used in Figure 1 were used, but with the addition of random noise having a distribution with standard deviation of 10. (A) With no thresholding, the Manders' co-localization coefficient at all instances of co-occurrence was found to be greater than 0.9. (B) With no thresholding, the RWC co-localization coefficient displayed a reduced dynamic range, although the response to co-occurrence was still linear. (C) With thresholding at 15% of the maximum intensity the Manders' co-localization coefficient was insensitive to correlation. At higher levels of correlation the thresholding eliminated the effects of noise, however at low correlation values the Manders' coefficient was still sensitive to noise. (D) With thresholding at 15% of the maximum intensity RWC showed a good response to both co-occurrence and correlation, as the threshold suppressed the effects of the noise.