Here's the result from debug_log.txt:
getMaxSpaceContainer(580, 580, William and Edwin.jpg, ): $s_width=580; $s_height=580; $newW=580; $newH=580;
cacheImage($imgfile=William and Edwin.jpg, $newfilename=/simon-gould-family-gallery/simon-gould-family-images-from-len-simms/William and Edwin.jpg_w580_h580.jpg, $allow_watermark=1, $force_cache=, $theme=zenpage-default) $size=, $width=580, $height=580, $cw=, $ch=, $cx=, $cy=, $quality=85, $thumb=, $crop= $image_use_side=longest; $upscale=0;
propSizes(, 580, 580, 1379, 1991, 1, longest, 402, 837)::$neww=580; $newh=580
cacheImage:William and Edwin.jpg: $size=, $width=580, $height=580, $w=1379; $h=1991; $cw=, $ch=580, $cx=, $cy=, $quality=85, $thumb=1, $crop=, $newh=580, $neww=580, $dim=580, $ratio_in=1.44379985497, $ratio_out=1 $upscale=0 $rotate= $force_cache=
propSizes(, 580, 580, 1379, 1991, 1, longest, 402, 837)::$neww=580; $newh=580
cacheImage:no crop William and Edwin.jpg:$size=, $width=580, $height=580, $dim=580, $neww=580; $newh=580; $quality=85, $thumb=1, $crop=, $rotate=; $allowscale=1;
Finished:William and Edwin.jpg