manual focus tips?

[bs0604]

I am intested in the manual focus question because I have been doing HDR where I need to bracket 3 photos. I have noticed that in autofocus mode (Nikon D90 --but hopefully soon to have my preordered D800) the lens will shift a few mm in between shots as I take the bracketed pics with the final image I imagine being degraded by the slightly different focuses of each picture. What I have been doing is either manually focussing to avoid this problem, or in AF mode halfway depress the shutter button to bring in to play autofocus and then switch the selector from AF to M on the lens barrell. Am I correct is assuming this is a proper way to handle this problem?

 

[Buckster]

I am intested in the manual focus question because I have been doing HDR where I need to bracket 3 photos. I have noticed that in autofocus mode (Nikon D90 --but hopefully soon to have my preordered D800) the lens will shift a few mm in between shots as I take the bracketed pics with the final image I imagine being degraded by the slightly different focuses of each picture. What I have been doing is either manually focussing to avoid this problem, or in AF mode halfway depress the shutter button to bring in to play autofocus and then switch the selector from AF to M on the lens barrell. Am I correct is assuming this is a proper way to handle this problem?

If you're on a tripod and the thing you've got your focus point on isn't moving, it shouldn't be an issue.

In any case, getting a focus lock and then switching to manual is a completely valid and effective way to deal with it.

 

[Buckster]

I'd love to compare the original screen with the replacement to see if there's something about the shape that's different and that might press or not press something in the focusing screen slot that activates/deactivates the AF illumination.

End facts, begin complete and utter speculation........ I'm new to photography, but mechanics and electronics I'm pretty comfy with. I don't reckon it's a mechanical issue (e.g. the shape of the screen or a tab on the side of it or something)... if so, Katzeye would have quite easily figured out how to get it to work and they wouldn't have this problem. My guess is that the AF illuminating lights are very very very low power and are introduced before the focusing screen, the light is enough to show up in the viewfinder but since that light source is so close to our eye the actual energy required to illuminate the point would be three fifths of #$%! all.... maybe due to the matte surface of the Katzeye the tiny itty bit of light is diffused enough that we can't see it, so simply by design the replacement screen just isn't capable of transferring that light to us? As I said, pure speculation... I'm more than likely wrong, but that's just my quick guess....

That being said, I'm now extremely curious to know why the 7D (and on your account the 5D) work while the x0D and below don't. There must be a difference in the system, maybe the light to illuminate the points in the 7D+ is introduced after the screen? I don't know, as I said I've got my speculating hat on now I'm sure someone who knows the really intimate workings of these cameras could tell us in a few words.

But this is good news for me, I was bummed when I read about the dots not working but I envision a 7D in the next couple of years so it's nice to know I can have the best of both worlds there

Curiosity got the better of my, so I simply contacted KatzEye Optics and asked. Here's their reply:

Hi Buck,

It's really pretty simple: in most SLR cameras with superimposed illuminated focus points, the illumination is accomplished by shining a light toward the focusing screen (from near the eye) and reflecting that light back to your eye with a tiny reflector. In some models, that tiny reflector is built into the focusing screen and manufacturing considerations are such that reproduction of the reflector in the small quantities used in this niche application is just cost-prohibitive, so the reflector is omitted and the light does not get reflected back to the eye. Thanks again for your interest in KatzEye Optics products and if you have any other questions, please feel free to ask.

Best regards,

Rachael Katz
KatzEyeT Optics

Mystery solved! :thumbup:

 

[DanPower]

Cheers Buckster, will keep that little gem of information stored safely until it's needed... BUT now we know why the x0D and below cameras DONT work, I'd love to know why the 7D+ cameras DO work! Must be a difference in the system, she quoted a cost issue and the replacement screens are similarly priced so it must have something to do with the in-camera system?

EDIT: never mind, I think it's already been answered....

In some models, that tiny reflector is built into the focusing screen