1. Mirror vs Optical lens + LED lighting test M Fitton, P Loveridge, J O’Dell RAL

2. High Power Targets Group Mike Fitton Mirror Lens Samyang 800mm MC IF f/8 Optical lens Tamron SP 150-600mm F/5-6.3 Di VC USD + Sigma 1.4X Teleconverter EX APO DG Fixed focal length = 800mm Fixed aperture = f8 Weight = 870g Focal length = 210-840mm (with 1.4x) Aperture = f8 - f32 (with 1.4x) Weight = 1951g

3. High Power Targets Group Mike Fitton Advantages of the optical lens Better resolution More contrast Variable focal length (Can fine tune image size) Variable aperture (Control depth of field, improved sharpness) No “donut” out of focus artefacts Longer Heavier More expensive Disadvantages of the optical lens

4. High Power Targets Group Mike Fitton Test setup Lens hood Tamron 150-600mm Sigma 1.4x teleconverter C-mount to Nikon adaptor (with aperture control) Megaspeed x7 Highspeed camera 1920 x 1080 pixels Sensor 13.2 x 8.8 mm 485mm (longest zoom) Distance from inner box window to camera sensor = 9.50m 386mm (longest zoom)

5. High Power Targets Group Mike Fitton Test setup A mock-up of the extra glass inside box to check for internal reflections Back wall Inner box window 3 extra glass windows

6. High Power Targets Group Mike Fitton Test setup White paint with black ink gridShot blast and engraved aluminium Resolution chart at forward most trough position Back wall of box Grid 10 - 0.28mm wide lines, 0.14mm gaps

7. High Power Targets Group Mike Fitton LED lighting Remaining reflections are a long way off the camera axis Final test should be done with outer box once modifications complete Position and angle of LED’s adjusted to reduce reflections. Final positions converted into engineering design of LED heatsink

8. High Power Targets Group Mike Fitton Focal length range at 9.5m 840mm 210mm Easy to frame the shot exactly as you want without moving the camera

9. High Power Targets Group Mike Fitton Transmission comparison Both lenses at f8 and the exposure time set in the camera to 90 microseconds. Camera sensitivity was set to the lowest setting of ISO 200 This would be good for 11,100 frames per second Mirror lensOptical lens Optical lens has slightly better transmission (brighter), but only just Optical lens has much better contrast and resolution (foreground and background) NOTE: Optical lens not zoomed enough so disadvantage in resolution comparison Crop area for resolution comparison (next slide)

10. High Power Targets Group Mike Fitton Resolution + DOF comparison Mirror lens f8 90  s (11k fps) Optical lens f8 90  s (11k fps) Optical lens ~f16+ 500  s (2k fps) Central frame - ISO 200 Focused on foreground resolution chart White gaps are 0.14mm wide

11. High Power Targets Group Mike Fitton Resolution + DOF comparison Mirror lens f8 90  s (11k fps) Optical lens f8 90  s (11k fps) Optical lens ~f16+ 500  s (2k fps) Edge of frame – ISO 200 Focused on foreground resolution chart

12. High Power Targets Group Mike Fitton Summary With the high speed cameras at RAL we have plenty of light, even at ISO 200 Megaspeed HHC X7 ISO 200 – 3200 Phantom v7.1ISO 4800 RedLake HG-100kISO ????  This would be useful information Mockup of experiment with 4 layers of glass showed no problematic reflections Optical lens has superior sharpness and contrast (centre to edge of frame) Optical lens has ability to stop down aperture to further increase sharpness and depth of field. Optical lens has ability to optimise image size regardless of optical path length Optical lens has slightly better transmission (brighter) We recommend the use of this optical lens