The focus lens is an add-on for the SFA light heads to produce a higher illumination intensity!
This is a simple adapter that slips over the front of your existing NIGHTSEA SFA light head and grips with a friction fit. It is available with two options for the focal distance: 30mm or 50mm.
No lens – illumination spot approximately 15mm diameter with the light head positioned 50mm from the surface.
50mm lens – central spot approximately 5mm diameter, intensity increase ~2x.
30mm lens – central spot approximately 2mm diameter, intensity increase ~3.5x.
The images below show the focus lens add-on and the effect. The three illumination spot images were made in manual exposure mode and are indicative of the relative intensity.
![MiniQGD_app_ferritin1.jpg](/images/uploaded/SFA-FL_comparison.jpg)
No Focus Lens
50mm Focus Lens
30mm Focus Lens
Considerations for lens choice:
To gain the benefit of the 30mm lens it is necessary to position the light head very close to the subject. This may be challenging in the tight space beneath a microscope objective. It might be more suited for photoactivation, where a high light intensity dose in a small area is often needed.
The 50mm lens provides a trade-off – brighter fluorescence, easier to work with.
Note – If the light head has a snoot installed that will have to be removed to use the focus add-on.