function [] = fluor_hist(start_dirname, experiment_path, save_flag)
    frame = 213;
    filenum = sprintf('%04d', frame);
    brightfield_thresh = 7500;
        
    fret_dir = start_dirname;
    cy5_dir = start_dirname+1;
    cy3_dir = start_dirname+2;
    txred_dir = start_dirname+3;
    
    fret_name = sprintf('%03d', fret_dir);
    cy5_name = sprintf('%03d', cy5_dir);
    cy3_name = sprintf('%03d', cy3_dir);
    txred_name = sprintf('%03d', txred_dir);
    
    fret_filename = [experiment_path '/IMAGES/RAW/' fret_name '/SC_' filenum '.tif'];
    cy5_filename = [experiment_path '/IMAGES/RAW/' cy5_name '/SC_' filenum '.tif'];
    cy3_filename = [experiment_path '/IMAGES/RAW/' cy3_name '/SC_' filenum '.tif'];
    txred_filename = [experiment_path '/IMAGES/RAW/' txred_name '/SC_' filenum '.tif'];
    brightfield_filename = [experiment_path '/IMAGES/RAW/999/WL_' filenum '.tif'];
    
    fret_img = imread(fret_filename);
    cy5_img = imread(cy5_filename);
    cy3_img = imread(cy3_filename);
    txred_img = imread(txred_filename);
    brightfield_img = imread(brightfield_filename);
    
    bead_mask = bwlabel(brightfield_img>brightfield_thresh, 4);
    
    num_objs = max(max(bead_mask));
    
    fret_beadpix = uint16(double(fret_img) .* double(bead_mask>0));
    cy5_beadpix = uint16(double(cy5_img) .* double(bead_mask>0));
    cy3_beadpix = uint16(double(cy3_img) .* double(bead_mask>0));
    txred_beadpix = uint16(double(txred_img) .* double(bead_mask>0));
    
    %should we be taking 1 val per object instead of assuming all beads are
    %same number of pixels? (i.e. we are sensitive to differences in size)
    fret_beadpix = reshape(fret_beadpix, 1000000, 1);
    cy5_beadpix = reshape(cy5_beadpix, 1000000, 1);
    cy3_beadpix = reshape(cy3_beadpix, 1000000, 1);
    txred_beadpix = reshape(txred_beadpix, 1000000, 1);
    
    fret_beadpix = fret_beadpix(find(fret_beadpix > 0));
    cy5_beadpix = cy5_beadpix(find(cy5_beadpix > 0));
    cy3_beadpix = cy3_beadpix(find(cy3_beadpix > 0));
    txred_beadpix = txred_beadpix(find(txred_beadpix > 0));

    fret_beadpix = fret_beadpix(find(fret_beadpix < 16000));
    cy5_beadpix = cy5_beadpix(find(cy5_beadpix < 16000));
    cy3_beadpix = cy3_beadpix(find(cy3_beadpix < 16000));
    txred_beadpix = txred_beadpix(find(txred_beadpix < 16000));
    
    fret_hist = hist(double(fret_beadpix), 16383);
    cy5_hist = hist(double(cy5_beadpix), 16383);
    cy3_hist = hist(double(cy3_beadpix), 16383);
    txred_hist = hist(double(txred_beadpix), 16383);
    
    figure; 
    hold on
    plot([1:16383], fret_hist, '.k');
    plot([1:16383], cy5_hist, '.r');
    plot([1:16383], cy3_hist, '.g');
    plot([1:16383], txred_hist, '.b');
    title(['Cycles ' fret_name ' - ' txred_name]);
    legend('FRET','Cy5','Cy3','TxRed');
    
    if(save_flag == 1)
        savefilename = [experiment_path '/QC/qc_fluorhist_' fret_name '-' txred_name];
        saveas(gcf, savefilename, 'bmp');
    end
    
