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Nikon DSLR Cameras
Out of Production DSLRs
D90
Service Question: getting AF and split prism focus screen to play "nice"
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<blockquote data-quote="jfairman" data-source="post: 108503" data-attributes="member: 11335"><p>D90 is 3+ years old. camera was showing rear focus behavior based on lots of careful tripod mounted test shots, several pros looking at test shots, service shop testing, etc.</p><p></p><p>found that I could get very accurate manual focus using split prism focus screen.</p><p></p><p>testing using nikor AF-S 35mm, shots at F1.8, variable speeds faster than 1/100, distance of ~1.5 ft, AF in single point ( center ) mode, natural light, remote triggered shutter</p><p></p><p>in addition to finding that AF put focus in test images behind the focus point, noticed that AF focused lens appeared "off" based on visible misalignment of focus point in split prism.</p><p></p><p>so i took the camera for AF service, to a reputable chicago based repair business providing service for customers throughout the US. the initial repair resulted in front focus shots. took the camera back for no-charge re-repair.</p><p></p><p>AF is perfect! now, images focused manually using the split prism focus screen are not in focus. as i write this i'm embarrassed to realize i don't know if they are front or rear focused, but most importantly the manual focus using split prism is no longer is accurate.</p><p></p><p>QUESTIONS: </p><p></p><p>is there a likely reason why correcting the AF behavior of the camera would cause the manual use of the split prism to no longer be accurate?</p><p></p><p>does the focus screen impact the AF behavior in any way?</p><p></p><p>is there any inherent problem with getting AF and split screen focus to agree?</p><p></p><p>i am planning to follow up with the split prism focus mfr to ask these same questions of them.</p><p></p><p>thanks in advance.</p></blockquote><p></p>
[QUOTE="jfairman, post: 108503, member: 11335"] D90 is 3+ years old. camera was showing rear focus behavior based on lots of careful tripod mounted test shots, several pros looking at test shots, service shop testing, etc. found that I could get very accurate manual focus using split prism focus screen. testing using nikor AF-S 35mm, shots at F1.8, variable speeds faster than 1/100, distance of ~1.5 ft, AF in single point ( center ) mode, natural light, remote triggered shutter in addition to finding that AF put focus in test images behind the focus point, noticed that AF focused lens appeared "off" based on visible misalignment of focus point in split prism. so i took the camera for AF service, to a reputable chicago based repair business providing service for customers throughout the US. the initial repair resulted in front focus shots. took the camera back for no-charge re-repair. AF is perfect! now, images focused manually using the split prism focus screen are not in focus. as i write this i'm embarrassed to realize i don't know if they are front or rear focused, but most importantly the manual focus using split prism is no longer is accurate. QUESTIONS: is there a likely reason why correcting the AF behavior of the camera would cause the manual use of the split prism to no longer be accurate? does the focus screen impact the AF behavior in any way? is there any inherent problem with getting AF and split screen focus to agree? i am planning to follow up with the split prism focus mfr to ask these same questions of them. thanks in advance. [/QUOTE]
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Nikon DSLR Cameras
Out of Production DSLRs
D90
Service Question: getting AF and split prism focus screen to play "nice"
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