Using a photosensor guided tracking system is not usually the best way to achieve solar tracking in relatively simple amateur tracking systems. A simple tracker may use more power than it saves by tracking, may point the panel to the wrong location and is more complex and expensive than technically better alternatives.
A simple mechanical gearbox and motor that tracks where the sun should be in a daily arc, and which is adjusted every few weeks for seasonal change, will be likely to be more cost effective overall than any more complex tracker.
A completely manually adjusted panel that is repointed to local noon every few weeks and which is kept clean (and ideally also cool) will outperform many optical trackers.
An optical 1 axis tracker with two sensors and a shield that allows both sensors to be equally illuminated when the panel is pointing at the sun is liable to be more than good enough.
Complex multi axis optical trackers will often cause complex multi axis problems.
For all except the very most exacting or purposes a 1 axis tracker is adequate that follows the arc of the sun across the sky. Adjustment for seasonal azimuth change can be made occasionally manually. Even as little as a few times per season may be good enough and once every week or two will get you about within the general noise margin due to other factors in your system.
It is usually good enough to drive your 1 axis tracker with a dumb drive algorithm that points the panels where the sun should be and returns it at day's end to wait the new dawning. Any day that the sun is not EXACTLY where it should be you have much bigger things to worry about than solar tracking!
You can get some minor gains by optical solar tracking with a good system. You can get substantial losses with a poor solar tracker. A good solar tracker allows the panels to point at the brightest area of sky when the sun is partially occluded but with enough output that the panel still makes some output. A good optical tracker will be able to decide which of a number of areas is brightest and ideally will have some ability to estimate how long the low sun condition will last so that it will not be waving the panels to and fro and using up energy and putting load on the drive unnecessarily. A good MPPT tracker will not get stuck on a false peak, will not hop from peak to peak for little or no gain and its sensors will match PV panel response so it is not pointing at a spot that is optimum for it but not for the panel.
A bad optical tracker may hunt unnecessarily, may use more energy in tracking to and for that it gains, may be a net maintenance liability, may get stuck on false MPPT peaks and may go hiving to an for chasing flitting bright spots when the sun level overall is too low to be worth the effort.
Which sort of optical tracker do you think the average amateur is most liable to build? ;-).
A well maintained and cleaned panel - and cooled if you can manage, that is pointed to local noon and suitable seasonal azumith angle and altered manually maybe weekly and otherwise not steered at all will give a good steered array a good fight and will not need a motor, gearbox, drive etc to be built.
IF you can cool a PV panel you'll get 10%+ more out on a hot day - more than you'll gain from most trackers.