having to use macro to see ground glass. - Page 3

Stuart Campbell · June 23rd, 2008, 05:37 AM

Hi Guys,
well I had a couple of hours spare this morning and re built the unit and set detail back to normal. There was a noticeable difference in the right direction unsurprisingly but chromatic aberation became more noticeable.

Lighting conditions were not perfect at the time of the test, but good enough to shoot in. There could have been a couple of other factors to explain the aberation now I think about it but I'm in too much of a hurry to investigate further.

Having improved the focus a little we are going to take it out and shoot some stuff with it on Thursday.

I'll post some results when we get back.

(still no contact from Letus. pretty poor customer service in my book!)

Ted Ramasola · June 23rd, 2008, 08:04 AM

Stuart,

take note that CA in this setup can be caused by two things.

1. your stock fujinon when its aperture at f2 and wider. you can isolate this by going for at least f2.8 or lower. Also the CA exhibited by the fujinon has the tell tale color of green and magenta.

2. the achromat. in my observation of the brevis and sgpro, this is tinted towards the blue and yellow colors. Not so sure about the CA from a letus achromat.

also , better edge to edge sharpness is achievable when your, at least, at f8 on the fujinon.

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June 23rd, 2008, 05:37 AM	#31
Stuart Campbell Major Player Join Date: Nov 2006 Location: Hannover, Germany Posts: 321	Hi Guys, well I had a couple of hours spare this morning and re built the unit and set detail back to normal. There was a noticeable difference in the right direction unsurprisingly but chromatic aberation became more noticeable. Lighting conditions were not perfect at the time of the test, but good enough to shoot in. There could have been a couple of other factors to explain the aberation now I think about it but I'm in too much of a hurry to investigate further. Having improved the focus a little we are going to take it out and shoot some stuff with it on Thursday. I'll post some results when we get back. (still no contact from Letus. pretty poor customer service in my book!)

June 23rd, 2008, 08:04 AM	#32
Ted Ramasola Major Player Join Date: May 2005 Location: Bohol Island Posts: 394	Stuart, take note that CA in this setup can be caused by two things. 1. your stock fujinon when its aperture at f2 and wider. you can isolate this by going for at least f2.8 or lower. Also the CA exhibited by the fujinon has the tell tale color of green and magenta. 2. the achromat. in my observation of the brevis and sgpro, this is tinted towards the blue and yellow colors. Not so sure about the CA from a letus achromat. also , better edge to edge sharpness is achievable when your, at least, at f8 on the fujinon.