Focus bracketing, why not?

Photoshop CS4 has a very neat Auto-Blend function that allows you to merge identical shots taken at differnt focal planes to generate a photograph with a larger DoF. There are also other tools to do the same thing. This is very nice because I can use my macro at 2.8 and still get all that great background blur with just the right DoF on my subject in the final product.

Now, after playing around with this for a while, I've wondered why cameras do not purposedly incorporate a focus bracketing function, just like they do it for exposure (some even have white balance bracketing ... who cares!). Just manual focus on the middle ground, press the shutter, and a series at different focal planes (with customizable intervals of course) is taken automatically. Wouldn't that be great?

cfibanez wrote in post #8386032
... (some even have white balance bracketing ... who cares!)....

I love having white balance bracketing and I couldn't care less about focus bracketing, honestly.

I read about this,
There is a camera that was set up to do this.. experimental.. can't recall the details. An interesting idea though.

Basically you can achieve some of it with aperture movn the shutter speed correspondingly

I asked the same question back in March '07.

Radtech1 wrote in post #2799681
And if not perfect AF, why not Focus Bracketing? Fire off three shots - one at my focus (or the suggested auto focus) and then one 5% on the close side of that and another 5% on the far side of that.

If I had that, my portfolio would be about 50% larger than it is.

Rad

And I agree, WB is not somthing that I find useful - but Focus Bracketing would be great.

HEY CANON, are ya listening??? Maybe that 5D MkIII?

Rad

Considering the precision, or rater lack of precision, in Canon's current implementation of autofocus, you can probably achieve this by simply taking three different pictures, where you let the camera do a new focusing operation each time.

Interestingly enough, when pronounced in English, "autofocus" sounds just like "out-of-focus".

apersson850 wrote in post #8386382
Considering the precision, or rater lack of precision, in Canon's current implementation of autofocus, you can probably achieve this by simply taking three different pictures, where you let the camera do a new focusing operation each time.

Interestingly enough, when pronounced in English, "autofocus" sounds just like "out-of-focus".

Ouch..............not too cynical then Anders

It sounds like it would be cool, but how about the practical application -- first of all, our DSLRs don't have an in-camera focal plane "mover" except for the very slight "micro" adjustment to the focus sensor that we use for MA. Plus, what unit do you suggest that the user be called upon to use? Degree of front-to-back field of view? Millimeters may even be too broad for a lot of macro photography.

Just sayin' it would not be some trivial "firmware" feature.

cfibanez wrote in post #8386032
...............
Now, after playing around with this for a while, I've wondered why cameras do not purposedly incorporate a focus bracketing function, ......

Interesting the Canon G10 has that.

tonylong wrote in post #8386401
It sounds like it would be cool, but how about the practical application -- first of all, our DSLRs don't have an in-camera focal plane "mover" except for the very slight "micro" adjustment to the focus sensor that we use for MA. Plus, what unit do you suggest that the user be called upon to use? Degree of front-to-back field of view? Millimeters may even be too broad for a lot of macro photography.

Just sayin' it would not be some trivial "firmware" feature.

Now you are either saying something I don't understand, or you have misunderstood how this works.
Indeed the camera has a focal plane mover. It's the focusing drive motor in the lens.
On the other hand, there's no adjustment made to the focus sensor, ever. That's not technically possible in today's cameras.

When the camera is focusing, the AF sensor measures how far out of focus the lens is. The lens AF motor is then commanded to run to a position that is calculated to bring the subject into focus. If the focus sensor is a bit "off", the lens will be driven to the wrong place, thus putting the focus plane in front of or behind the image sensor plane. Outside a camera repair center, there's nothing that can be done about the focus sensor. But something can be done about the lens drive. So when you microadjust the sensor, you actually do nothing at all to the sensor, but apply an offset to the data that's computed, based upon information from that sensor.
If you've ever used a rifle in sidewind you know how it is. You can't stop the wind from blowing, but you can aim a bit off your target, and thus compensate for the drift. Same thing here. You can't fix mechanical problems with the AF sensor or sub-mirror, but you can compensate by focusing off-mark a bit in the other direction.

So for sure it could be done with firmware alone. As for the units to use, why not do as with the AF micro adjust, where they just gave us some arbitrary units? Less granular in this case, but same principle.

Heh, that's funny, you're right, I was thinking strangely enough from a MF viewpoint! So, yeah, having the AF function recalibrate with, like you say, an arbitrary unit +/- value should work sure (he who knows nothing about it boldy says).

It's a good idea. I like it.

But can't you do that by controlling depth of field by closing up the aperature and slowing the shutter speed?

apersson850 wrote in post #8386382
Considering the precision, or rater lack of precision, in Canon's current implementation of autofocus, you can probably achieve this by simply taking three different pictures, where you let the camera do a new focusing operation each time.

Interestingly enough, when pronounced in English, "autofocus" sounds just like "out-of-focus".

I really don't get it, unless you are taking an unsubstantiated jab at Canon?

I can see how the focus bracketing can be used by some people, that would be neat. I probably wouldn't use it though.

I still don't get it. Why? You may as well shoot at F11 or F13 to start with.

Just get a p&s plenty of dof there...