# Is there a D90 Movie Mode Autofocus hack?



## supraman215 (Jul 21, 2010)

I didn't know where else to post this but is there a firmware hack that allows one to autofocus while filming in movie mode with the D90. I need a new camcorder and I wanted to see if I could put off the purchase a little longer and get by with my D90 but the autofocus in movie mode is really holding me back. Thanks.


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## supraman215 (Jul 22, 2010)

bump


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## MohaimenK (Jul 22, 2010)

you might want to try a nikon forum


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## KmH (Jul 22, 2010)

supraman215 said:


> *Is there a D90 Movie Mode Autofocus hack?*


 No.


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## Big Mike (Jul 22, 2010)

I might be wrong, but I think the issue is that the mirror needs to be down for the AF to word, that works for still photos because the mirror is down until right before the shutter opens, but that obviously won't work for video mode because the mirror has to be up.

On models that do have AF during movie mode, but they use some sort of contrast detection AF system, pretty much like most P&S digital cameras.  From what I understand, it's not nearly as fast/good as the regular AF system in your DSLR.


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## KmH (Jul 22, 2010)

In virtually all 35 mm format dSLR cameras the auto focus module is in the bottom of the body.

The main mirror is only 50% reflective, passing 1/2 the light from the lens up to the viewfinder, and the other 1/2 on through the main mirror to a second smaller mirror behind it that reflects the other 1/2 of the light down to the AF module.

Like Mike said, the mirror has to be up to shoot video, so no AF from the still shot AF module, and hence *no hack*.


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## supraman215 (Aug 2, 2010)

Then how does it AF in live view mode when taking stills?


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## MrBarney (Aug 2, 2010)

Either:

It quickly flips the mirror down, focuses, then flips it back up and takes the shot.  (phase detect, or "Quick" AF on a Canon)

Or:
it uses contrast detection like a P&S ("Live" AF on a Canon) which can also perform face detection on some cameras.  This is painfully slow (up to 1 second) as the lens hunts for the highest contrast.


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## Neil S. (Aug 2, 2010)

Big Mike said:


> I might be wrong, but I think the issue is that the mirror needs to be down for the AF to word, that works for still photos because the mirror is down until right before the shutter opens, but that obviously won't work for video mode because the mirror has to be up.
> 
> On models that do have AF during movie mode, but they use some sort of contrast detection AF system, pretty much like most P&S digital cameras. From what I understand, it's not nearly as fast/good as the regular AF system in your DSLR.


 
Thanks Big Mike, I didn't know this.

OP: Ya I find the lack of AF when doing video on my 7D is quite annoying as well.

The video that it produces is so beautiful, but having to manual focus is a pretty large limiting factor in my opinion.

When I try to record my son playing, I seem to lose focus a lot because he moves so much/quickly.


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## Neil S. (Aug 2, 2010)

supraman215 said:


> Then how does it AF in live view mode when taking stills?


 
I am pretty sure it uses that contrast detection thing Big Mike mentioned.

The AF in live mode on my 7D is super slow compared to normal shooting. It is also far more likely to fail alltogether, and I have to manual focus a lot.


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## Neil S. (Aug 2, 2010)

MrBarney said:


> Either:
> 
> It quickly flips the mirror down, focuses, then flips it back up and takes the shot. (phase detect, or "Quick" AF on a Canon)
> 
> ...


 
I didn't really know this. Thanks. :thumbup:

I do remember now seeing two types of AF in the live view settings. I just didn't know the difference.


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## djacobox372 (Aug 2, 2010)

Is manual focus really that hard?  Autofocus and movie making seems extremely problematic.


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## Neil S. (Aug 2, 2010)

djacobox372 said:


> Is manual focus really that hard? Autofocus and movie making seems extremely problematic.


 
Umm...

Camcorders?

I don't exactly know how they do their magic, but it has to be some kind of AF.

Yes it is difficult, you can lose focus quite easily and need to hunt for it constantly on moving stuff.

DSLR video seems to be the best suited to recording non moving or slow and predictable moving stuff.

From my experience it would be extremely difficult to shoot fast moving stuff, like car racing for example. 

I guess with a lot of practice it could be possible to aquire focus fast and keep it, this would take a lot of skills though. Far more than I have at this time.

Imagine shooting stills of something like motorsports or certian types of sports without autofocus. Its pretty much the same thing really. Its very possible, but much harder without it.


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## supraman215 (Aug 2, 2010)

My erratically moving subject is what spawned the question. But I bought a new camcorder anyway, because I figured this was not possible.


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