Is focus peaking an alternative AF Fine Tune method on suitable DSLR cameras?

If you would like to post, you'll need to register. Note that if you have a BCG store account, you'll need a new, separate account here (we keep the two sites separate for security purposes).

soundbyte

soundbyte

A well known member 🇦🇺 📷
Supporting Member
Marketplace
Member's gallery
I have not seen this auto fine tune idea before, have I missed something?
Crazy idea?

If you have a DSLR camera that does focus peaking you might like to try this to check/set your AF Fine Tune values.
Not sure if it works for all cameras with focus peaking (I think it should) hence my question.

Mount camera on a sturdy tripod or other platform(?).
Setup a suitable target with a ruler at 45 degrees at a reasonable distance from your camera.
Target_Used_150821.JPG
You can only see EXIF info for this image if you are logged in.


Switch on the camera, make sure you have focus peaking on, set focus to auto, set the aperture to fully open, move the lens focus ring to infinity, push whichever button is your focus button and let the camera focus.
Carefully move the AF button to manual, switch the camera to live view, magnify the image and see where the highlights are on the target, especially on the ruler.
You should see where the highlights start/end on the ruler.

If your highlights are not where you would like them to be, enter the Menu to adjust your auto fine tune value and retest.
You should be able to see where the peaking point has moved on the target and can set it to your taste.

Difficult to photograph the magnified live view screen!
In Focus or really close, maybe a little bit front focusing.
In_focus_150821.jpg
You can only see EXIF info for this image if you are logged in.


Back Focusing
Back_Focus_150821.jpg
You can only see EXIF info for this image if you are logged in.


Front Focusing
Front_Focus_150821.jpg
You can only see EXIF info for this image if you are logged in.
 
Member's gallery
Pistnbroke said:
You dont need all this sturdy tripod rubbish if you use flash and often doing it at the widest aperture will give such poor definition you cannot tell anything ..try f5.6
Click to expand...
Not sure what you are referring to here?
This is about finding the actual focus point of your camera / lens combination using the auto fine tune setting of a camera if it has focus peaking.
This idea uses live view to test the focus point, no viewfinder needs to be used, no shots need to be taken, no flash needed, wide aperture useful to limit the DOF (my test was at 5.6, wide open, tick), as well as a well lit target.
To conduct this test you are best served by putting the camera on a tripod.
 
Member's gallery
Looks pretty simple. Time saver for sure. I've always wondered about the accuracy of using contrast focus for tuning a camera that will be using phase detect when shooting. But the built in auto tune functions do it that way and we assume the manufacturer knows what they're doing. Although on mine the auto function has never given even close to the same results as when I do a bench test :(
 
Member's gallery
@NorthernFocus thanks for the comments.
It will be interesting to hear results from others who may test this idea.
It is pretty simple and quick but that is only useful if the results are reliable and accurate.

I think that using a remote shutter release for focusing the camera could be a worthwhile added extra step, less camera movement.
A bit more setup needed to change from BBAF to the half press shutter button focus, something to try, later today.

The internal auto fine tune function in my experience is the same as yours, not repeatable/reliable.
That may have been my testing abilities, me not being able to hold down two buttons at one time without moving the camera.
 
Member's gallery
I did not get around to testing the use of a remote shutter release for doing the autofocusing until this morning.
Note to self, remember to reset the shutter button AF activation to off when testing completed!

The addition of the remote shutter release for actuating autofocus definitely made a difference, minimal camera shake during focus acquisition, more repeatable results.
 
Member's gallery
Anyone tested this focus peak mentioned above with D850 and 200-500 f5.6E? Can this sort of method work as well to test lens - AF tune in the field when the natural light is present? Very interesting method btw 🤔. If AF tune the 200-500, you do the focus peak at 200, 300, 400 and 500 at f/5.6?
 
Member's gallery
ales44 said:
I shoot at something like 300mm to 500mm, so it would be 300-400-500mm.
Click to expand...
Great, no harm in checking all three but pick one if you'll actually perform AF Fine Tuning on the lens as you can only enter one fine tuning value.

And remember, fine tuning doesn't make a lens any sharper than it already is, it just aligns the camera's AF system so that what the camera thinks is best focus distance is actually best focus distance. IOW, it makes up for small optical path differences between the DSLRs focus sensor and the main image sensor. It won't make a sharp lens sharper, but it can make the AF system more accurate and fix front focus or back focus issues.

Another way to say this is that when focusing using the main image sensor while in Live View mode focus fine tuning doesn't come into play. When focusing through the viewfinder where the camera bounces some light off the mirror to a separate focus sensor there can be errors and focus fine tuning can correct for those errors. That's why the Focus Peaking method described in this thread or the Dot-Tune method work for checking fine tuning, in either case you're basically comparing the focus achieved in Live View to the focus achieved in normal viewfinder AF operation and seeing if they're the same or different. Only perform fine tuning if they're different.
 
Member's gallery
DRwyoming said:
Great, no harm in checking all three but pick one if you'll actually perform AF Fine Tuning on the lens as you can only enter one fine tuning value.

And remember, fine tuning doesn't make a lens any sharper than it already is, it just aligns the camera's AF system so that what the camera thinks is best focus distance is actually best focus distance. IOW, it makes up for small optical path differences between the DSLRs focus sensor and the main image sensor. It won't make a sharp lens sharper, but it can make the AF system more accurate and fix front focus or back focus issues.

Another way to say this is that when focusing using the main image sensor while in Live View mode focus fine tuning doesn't come into play. When focusing through the viewfinder where the camera bounces some light off the mirror to a separate focus sensor there can be errors and focus fine tuning can correct for those errors. That's why the Focus Peaking method described in this thread or the Dot-Tune method work for checking fine tuning, in either case you're basically comparing the focus achieved in Live View to the focus achieved in normal viewfinder AF operation and seeing if they're the same or different. Only perform fine tuning if they're different.
Click to expand...
thank you, will give a try then and see how it goes 👍
 
I think focus peaking is about the same as using the auto focus. The only difference in my mind is with focus peaking you are turning the ring and asking the auto focus system if it agrees with you (If yes, then glow red!). So it's just another way to approach it, but it seems more convoluted than just telling the AF to do its thing in the first place.
 
Last edited:
Member's gallery
I tried the focus peaking method to AF fine tune my Nikon D850 with sigma 300-800 lens. I couldnt get reproducible results, so went back to my standard dot tune method. Thankfully I have switched to mirrorless and dont have to worry with AF fine tune anymore.
 
Member's gallery
I agree with Bill. I have a M4/3 system that I use for non-wildlife shots, and as backup sometimes. I find that using manual focus with peaking gives the same results as AF-S and AF-C, but is slower. So I hardly ever use it. In a dSLR, focus peaking can only be used in live view, so it seems rather pointless to me. But I have a related question - All the detailed instructions on line for the various methods of calibrating focus in dSLRs say Use AF-S. But in real life, for all my bird and wildlife photography, I use AF-C, generally with back-button focus. So do the instructions using AF-S also apply when using AF-C? Thanks.
 
Member's gallery
Thanks @Ed Erkes for your comments, it would be ineresting to know if the Sigma lens was the problem, I have various Nikon lenses and all produce good repeatable results with this method.

This method of AF Fine Tune uses the cameras in built focus peaking facilities to check the focus aquired and provides a real time in camera display for that aquired focus.
The photos above show how the camera "sees" the focus point and displays that in "Live View".
It can be seen that the camera shows where it has determined focus to be with back, front and in focus "Live View" display samples.

Both AF-S and AF-C (I use AF-C) can be used to aquire focus but as you then switch to manual focus to see the result in "Live View" it is a moot point as to which one should be used.

This method has provided me with reliable and repeatable AF Fine Tuning values for my camera/s len/es combinations.

Give it a try it may be of some use, please inform us of the results of your AF Fine Tune testing.
 
You must log in or register to reply here.
Back
Top