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2/3rds rule or crop

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Martin Muehlemann

Martin Muehlemann

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Hello everyone

Since six month I have now my A850. In the meanwhile a got pretty used to it. Nevertheless I have some doubts while shooting. I would like to have your feedback on this.

All my lenses are good performers in general. However, when having bright light or low light situations all the off-center AF sensors tend not to get focus. Either never or not on time to capture the subject

I have learned that only the central AF sensor is a dual cross sensor (f/2.8). Which limits the options to compose a picture with the 2/3rds rule.

On my Olympus E-30 is had 11 double cross AF sensors (f/2.8). No issue decentering the subject.

How do you do this?
Do you all use the central sensor for this?
Am I the only one in the need of more dual cross AF sensors?

Thanks for your feedback

Cheers
Martin

--

Sony Alpha 850 | Sony ZA Vario-Sonnar T* 24-70 SSM | Sony 50/1.4 | Sony ZA Sonnar T* 135/1.8 | HVL-F20AM

http://www.muehlemann-pix.ch
http://www.fotocommunity.de/pc/pc/mypics/1125341
 
f I'm reading your question correctly, you can accomplish this by focusing and recomposing -

1.aim the center focus spot at the subject - half press the shutter to lock focus
2. While keeping the shutter half pressed, re-compose the shot to your liking,
then fully press the shutter to take the shot.

In most cases the shift will not effect focus. The other option is manual focus.
--
more bONGO at
http://www.thebongolian.com
http://www.bongolia.com
 
bongo said:
In most cases the shift will not effect focus. The other option is manual focus.
Click to expand...
Focus with half-press shutter on intended main subject, lock focus with the AF/MF button, recompose with correct framing, release shutter, unlock focus with AF/MF button.

Basically using the AF/MF button as a hold-focus button, but toggled.

The advantage of this process is that exposure is correct wrt to the correct framing. But it takes to button presses more. And the difference may only be visible if there is large exposure difference between the two framings.

Regards,
Mike
--
I'd prefer my DSLR without video, thank you.
I know it has uses, but not for me.
I like the NEXes, but they are too small for my hands.
 
Some the of the higher end lenses have focus-hold buttons to help with this problem - see also my other post.

Regards,
Mike
--
I'd prefer my DSLR without video, thank you.
I know it has uses, but not for me.
I like the NEXes, but they are too small for my hands.
 
I mostly crop on a900. In worse lighting, the horizontal and vertical points (single F2.8 I think) do the job. In bad lighting the center point is the only way to go. Recomposition is an option, unless you have wide aperture (an you have). Than better do not recompose, just crop, as it is likely you loose the critical focus point.
 
Mike CH said:
Focus with half-press shutter on intended main subject, lock focus with the AF/MF button, recompose with correct framing, release shutter, unlock focus with AF/MF button.

Basically using the AF/MF button as a hold-focus button, but toggled.

The advantage of this process is that exposure is correct wrt to the correct framing. >
Regards,
Mike
Click to expand...
You're confusing me here. Are you saying that the half-press shutter locks the exposure??? - TF
 
OldClicker said:
Mike CH said:
Focus with half-press shutter on intended main subject, lock focus with the AF/MF button, recompose with correct framing, release shutter, unlock focus with AF/MF button.

Basically using the AF/MF button as a hold-focus button, but toggled.

The advantage of this process is that exposure is correct wrt to the correct framing. >
Regards,
Mike
Click to expand...
You're confusing me here. Are you saying that the half-press shutter locks the exposure??? - TF
Click to expand...
In multisegment mode, the exposure is locked with half press of the shutter when focus locks. In spot or CW it does not lock.

tom
 
Martin Muehlemann said:
Hello everyone

Since six month I have now my A850. In the meanwhile a got pretty used to it. Nevertheless I have some doubts while shooting. I would like to have your feedback on this.

All my lenses are good performers in general. However, when having bright light or low light situations all the off-center AF sensors tend not to get focus. Either never or not on time to capture the subject

I have learned that only the central AF sensor is a dual cross sensor (f/2.8). Which limits the options to compose a picture with the 2/3rds rule.

On my Olympus E-30 is had 11 double cross AF sensors (f/2.8). No issue decentering the subject.

How do you do this?
Do you all use the central sensor for this?
Am I the only one in the need of more dual cross AF sensors?

Thanks for your feedback

Cheers
Martin
Click to expand...
It is a problem when using continuous focus and you want to track a moving subject at the 1/3'rds points. One of my greatest wishes for an advanced a-mount camera is cross sensors at or very near the thirds points (as well as just more in general.)

With static subjects I use AF-A and focus and recompose.

I have found that with moving subjects I get a much better hit rate by using the AF/MF button on back as follows:

1. set AF-C on camera
2. set AF/MF button to "hold" in the menu
3. press and hold the AF/MF button - switches to MF
4. rough pre-focus

5. while holding the AF/MF button in place the desired AF sensor (make sure you are in local mode and its the one that is set) over the part of the subject where you want focus.
6. half press the shutter
7 release the AF/MF button - the subject should snap into focus and track.
8 press shutter all the way.

Note it takes longer to read the instructions than to carry them out. I have a couple of shots reproduced below from my Maxxum 7 (with the same controls) where I was trying to photograph a moving blue heron, and the camera would not lock on (I was using an old 400mm lens). Using the above technique I was able to lock onto the eye as the bird raised its head and track it as it moved ts head to the position I wanted.

tom







 
Under menu screen 3, select AF w/ shutter. Setting this option to "off" will prevent the shutter button from focusing. Rather than the shutter button, autofocus can now be accomplished by pressing the center toggle of the multi-selector. I find it easier to use this method (and keep the camera set this was as default) rather than using the MF/AF button.

--
Regards,
Graham

'I photograph to find out what something will look like photographed.' -Garry Winogrand
 
i mostly use the center AF sensor and recompose. focus problems due to the recomposing are very rare. that's for more or less static subjects. when the subject is moving too fast, cropping is probably the way to go - at least that's what i do.
 
Thanks Tom. Recomposing presents itself quite difficult. Wide Open, at night, in city and you'ld like to capture some street act or so. A slight movement and you end up out of focus.

At the airshow, an F-18 passing a 450knots and distance 300m you might not want to recompose. So center AF seems to be the only way.

Taking picture of my children won't allow to recompose. Focus must be perfect at first go. My experience so far, out AF focus point end up in nowhere, even with the Zeiss.

I was birding during my stay in Mallorca in National Park. There indeed you have lots of time to compose and recompose. Got quite a few nice shots.

Cheers
Martin

--

Sony Alpha 850 | Sony ZA Vario-Sonnar T* 24-70 SSM | Sony 50/1.4 | Sony ZA Sonnar T* 135/1.8 | HVL-F20AM

http://www.muehlemann-pix.ch
http://www.fotocommunity.de/pc/pc/mypics/1125341
 
Martin Muehlemann said:
Thanks Tom. Recomposing presents itself quite difficult. Wide Open, at night, in city and you'ld like to capture some street act or so. A slight movement and you end up out of focus.

At the airshow, an F-18 passing a 450knots and distance 300m you might not want to recompose. So center AF seems to be the only way.

Taking picture of my children won't allow to recompose. Focus must be perfect at first go. My experience so far, out AF focus point end up in nowhere, even with the Zeiss.

I was birding during my stay in Mallorca in National Park. There indeed you have lots of time to compose and recompose. Got quite a few nice shots.

Cheers
Martin
Click to expand...
I have used the method I described for air shows with my Maxxum 7. I haven't had the chance to try yet with my A700, and it worked as long as I could line up with the plane when it was a distance away, or if it was doing a slow pass (Blue Angels in landing configuration, slow at high angle of attack.) But if it was a quick pass from behind and then going overhead (before all the restrictions on crowd location) it was almost impossible, and even with the center sensor it was very difficult.

Where I've been able to prefocus on a fixed point (for example in a auto race where the car will appear from a blind turn), it also works. It is important that the actual subject be almost in focus when AF kicks in so the camera doesn't start to hunt (usually the wrong way).

tom
 
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