Would this much micro adjustment account for this much misfocus?

dubcat

dubcat

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Amir
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Hi,

I finally got round to trying out a test to set the micro adjustment on my canon 50d with 17-55 2.8 lens mounted. I had to dial in 7 on the micro adjust at both 35mm and 55mm to get the best shot. Based on your experience would this account for the lens front focussing about an inch when at 50mm and with the subject about 4 feet away?

Dub
 
Dub- this is a difficult one to answer mate. So much depends on how you carry out these tests - you need to be very methodical, using a tripod and a suitable test target.The distance of the test target can also be critical. If you do a search you should find loads of posts on how to go about lens calibration.

For what it's worth I've tested all my lenses umpteen times and it's easy to convince yourself there's a problem where there isn't one. I drove myself potty with this for a while, but now the calibration for all my lenses is set at zero (default) with both DSLRs I use. If there is a problem with any of them it's well within the bounds of normal image sharpening in post processing to sort out anyway.

That's not to say you may not have a problem, but the way you go about conducting the tests is pretty critical.

It's recommended to take three exposures (for consistency) each time you vary the setting - both - and + adjustments in increments of 5. These are very tiny adjustments - almost negligible.

I find the fact that you're getting an identical result with two different lenses a bit questionable although not impossible.
 
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Hi CT - i am getting the identical result with the same lens set at two different focal lengths :) I spent a LONG time doing this - probably well over an hour actually. I followed this procedure.

http://www.stanford.edu/~ahazeghi/Photos/MA-web/

I must admit afterwards I realised I missed a step and I probably need to go and do the whole thing again at some point. I do still think I did a reasonably good test though. Anyway, I was just wondering how big 7 on the micro adjustment scale on the 50d is ..

I have been consistently missing shots for about two years now i.e. since i bought this current lens and camera. Here is the latest miss from today which finally motivated me in to taking action (this is a crop at 100% - the rules are 800px max right?):

crop.jpg


I am 100% sure i focussed on the eye and i am also reasonably sure i did not move the camera after focussing. As you can see the hand is in focus rather than the eye. Was wondering if 7 on the microadjust would account for this. This was taken with a 1.6x crop camera at 44mm f/2.8.
 
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1024 pixels on the longest side is the new max size limit if the image is hosted elsewhere - not sure if that applies to images hosted here on TP too - anyway this image is plenty big enough as long as it's a 100% crop.

7 on the adjustment scale is a tiny amount and wouldn't account for the distance between the end of his nose and the eye. The full 50 adjustment scale is only a small amount in real terms and certainly wouldn't account for the distance between the front edge of that hand and the eye.

Which focus spots were you using? Which AF mode?

Can you post an 800 pixel version of the full image?
 
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CT said:
1024 pixels on the longest side is the new max size limit if the image is hosted elsewhere - not sure if that applies to images hosted here on TP too - anyway this image is plenty big enough as long as it's a 100% crop.

7 on the adjustment scale is a tiny amount and wouldn't account for the distance between the the end of his nose and the eye. The full 50 adjustment scale is only a small amount in real terms and certainly wouldn't account for the distance between the front edge of that hand and the eye.

Which focus spots were you using? Which AF mode?

Can you post an 800 pixel version of the full image?
Click to expand...

I used the centre spot I think. I will post the bigger image tomorrow and check the focus point in dpp too. Am in bed now on the iPad. So it sounds like my misses are not explained by the micro adjustment, as you initially pointed out. Back to the drawing board :(
 
I was gonna suggest if you use DPP check the AF point. :thumbs:

In bed on the iPad - thats sad! :lol:
 
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CT said:
I was gonna suggest if you use DPP check the AF point. :thumbs:

In bed on the iPad - thats sad! :lol:
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Only because you've got an entire bedside workstation and consol set up! :lol:

It definitely looks like missed focus to me, but it'd be easier to judge with a) an uncropped copy of the original and b) a screen print from DPP showing the focus point as mentioned.
 
Dub,

Hot humids nights aren't the best for heavy maths but I've done a calculation based on your 50mm focal length at 1220mm subject distance shot at f/2.8 and come up with 26.25mm offset for an MA value of 7

There will be some error in the calculation because I have no way to know the true focal length of the lens when it's focussed so closely...it'll certainly be less than the 50mm indicated which assumes focus at infinity.
This error will make the 26.25mm calculated value be somewhat lower than the real value. I'm disinclined to try to guess the actual focal length as this would just add another inaccurracy to the final figure.

Bob
 
That pic is too far out for it to be anything but user error. And it's a poor example from which to draw hard conclusions because of all the potential variables. Sorry.

If you want to know what a 7 on the microadjust looks like in terms of distance, then set up a suitable target at your chosen settings (search 'cerial box' against my user name) and take two shots, one at zero and another at 7, and measure the distance between the two points of sharpest focus. But it will be a lot less than shown in the example image.

Edit: just seen Bob's post above. 26.25mm... :thinking:
 
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HoppyUK said:
Edit: just seen Bob's post above. 26.25mm... :thinking:
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One unit of MA is 1/8th of the single sided depth of focus (ie, in the image plane) at the aperture and focal length (strictly magnification) used.

A test similar to yours Richard....
Set MA to -20
Take test shots of a subject and progressively move the subject until sharp focus is achieved.
Set MA to +20 and repeat the above.
The difference in subject position for the two acceptable shots will allow calculation of the MA value versus focus offset for that particular FL and subject distance (lens aberrations not withstanding).

Bob

Bob
 
Canon Bob said:
One unit of MA is 1/8th of the single sided depth of focus (ie, in the image plane) at the aperture and focal length (strictly magnification) used.

A test similar to yours Richard....
Set MA to -20
Take test shots of a subject and progressively move the subject until sharp focus is achieved.
Set MA to +20 and repeat the above.
The difference in subject position for the two acceptable shots will allow calculation of the MA value versus focus offset for that particular FL and subject distance (lens aberrations not withstanding).

Bob

Bob
Click to expand...

You should be able to calculate it from that. I didn't know it was 1/8th of one side of the depth of focus :thumbs:

But 26mm is just way too far...
 
There's a fair bit of noise visible (not that I mind) - was this shot at the lowest ISO setting to give the cleanest image possible? No point trying to ascertain focus when you're fighting against the sensor's capabilities.....

IMO, it does look a little soft but it's a big crop and at that magnification you do start to loose that pin-sharpness and start seeing the actual pixel make-up of the image.

I haven't checked your exif but it looks like DofF is limited anyway, judging by how much of a shift there is from the front of the hand to the subject's eye. Maybe doing a tripodded still-life could yield more conclusive results.....
 
Really appreciate the help guys. Bob - that is a fantastic effort with the maths!!! Really impressed - especially given the time of night you did it :)
 
Guys - I checked in dpp and no active focus point is showing. I must have recomposed - i am such an idiot. I still don't get why this would result such a big change in the focus point but since it invalidates my test i will start over today. I will post in this thread with my new findings and I would really appreciate it if you would bear with me and respond once i have done that.
 
dubcat said:
Guys - I checked in dpp and no active focus point is showing. I must have recomposed - i am such an idiot. I still don't get why this would result such a big change in the focus point but since it invalidates my test i will start over today. I will post in this thread with my new findings and I would really appreciate it if you would bear with me and respond once i have done that.
Click to expand...

Don't worry about it. :D

With a shot like the shot of the child use a single AF point - try the centre one for now and forget about composition - just concentrate on getting that AF spot on the eye and use continuous servo AF. Humour me - see what you get.
 
dubcat said:
Guys - I checked in dpp and no active focus point is showing. I must have recomposed - i am such an idiot. I still don't get why this would result such a big change in the focus point but since it invalidates my test i will start over today. I will post in this thread with my new findings and I would really appreciate it if you would bear with me and respond once i have done that.
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Comments on that image I would make contributing to possible misfocus, bearing in mind we're looking at a couple of cms

Any kind of focus-recompose technique alters the distance, and the further the movement off-centre, the more there is. It's easy to lose 1cm like that.

Then there is the delay between focusing and shooting, during which time both the camera and subject can move (though maybe not the subject in this case). Just breathing changes things.

Then there is the focus point itself which, even if placed absolutely accurately, can pick up on the wrong thing. It's quite a bit bigger than the square in the viewfinder, and larger still with AF expansion enabled. It's natural inclination is to pick up on brighter areas nearer to the camera, and it's easily possible that even when placed over the eye it has picked up on the hand in that shot.
 
CT ok i will give that a go and use cropping to get the composition i want. I remember what i did though here.. I chose a focus point close to the eye.. and then only very slightly recomposed. I was very conscious of the impact of recomposing and honestly don't believe I could have done it enough to cause such a big shift in the focal plane.

Hoppy that actually explains what i suspected might be happening! I often find the focus locking on to something bright and shiny that is not what i considered to be particularly close to my focus point. I guess in this case maybe the eye area which is in shade was outdone by the brightness of the hand.

I realise now why my focus points are now showing in dpp too. I shoot in one shot af. I use the af-on button to lock focus and then i release the button and take my shot... so the focus point is not recorded.

I took some shots of a test chart using both normal view (i.e. through the viewfinder) and live view. It seems that micro adjustment has VERY VERY VERY little impact - in fact i can hardly discern any difference with the setting at 7 vs the setting at 0.

This is really doing my head in - I tried so hard to not be the problem (i.e. to eliminate user error). And it still keeps happening. I can't be THIS useless surely? :(
 
Here are two photo's i took of lens charts - the first is with zero micro adjust and the second with 7 micro adjust. I cant see a difference. These are 100% size crops. The actual focus point is to the right out of shot, level with the text that should be in perfect focus.

They look the same to me.

chart-MA-0.jpg

zero micro adjustment

chart-MA-7.jpg

seven micro adjustment
 
dubcat said:
I realise now why my focus points are now showing in dpp too. I shoot in one shot af. I use the af-on button to lock focus and then i release the button and take my shot... so the focus point is not recorded.

(
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You have to realise that in one shot AF mode once you achieve focus, the focus is locked until you actually press the shutter. Any delay in pressing the shutter gives ample opportunity for you and/or your subject to move slightly and throw the shot out of focus. I almost always shoot in Servo AF Mode for this reason - you have the focus being continually finely adjusted until you actually press the shutter button.

Take plenty of practice shots to see the difference, and really work on your basic hand holding technique - it's easy to get complacent and too casual about it. Many an experienced photographer has suddenly noticed their images not quite as sharp as they could be and had to go back to basic technique.

Let us know how you get on.
 
Dub - you can see from the above shots that you're not even lined up parallel to the test chart. Seriously, forget the micro adjustment for now - go and take some real world shots doing what I suggested above and let's see the results. :)
 
I am parallel - i have just cropped from one side of the test chart so you are just seeing perspective distortion from one half of the picture. I do now realise at least that microadjust has a minimal impact. I am sort of at my wits end to be honest. I see children photographers achieving almost magical focus which has eluded me completely. It's not just the odd miss.. it's every time. I have never used my lens at f/2.8 successfully ... about ready to give up. Still I should save myself a fortune in fast glass there is no point in buying :(
 
dubcat said:
I am parallel - i have just cropped from one side of the test chart so you are just seeing perspective distortion from one half of the picture. I do now realise at least that microadjust has a minimal impact. I am sort of at my wits end to be honest. I see children photographers achieving almost magical focus which has eluded me completely. It's not just the odd miss.. it's every time. I have never used my lens at f/2.8 successfully ... about ready to give up. Still I should save myself a fortune in fast glass there is no point in buying :(
Click to expand...

Have you established that there's nothing wrong with your camera/lens? It's unlikely, and what you have posted so far appears inconclusive, but it's possible. Try the cerial box test, it takes me two minutes - have you checked all those other AF microadjust threads?

If the kit's okay, then it must be technique - and remember that for every one of those great images you've seen, there might be ten duffers that you haven't.

Get some practise in. Use the centre-point, make sure the AF point expansion is off, and use servo. Pin that AF point over the nearest eye and make sure it stays there. Shoot plenty :thumbs:

You can hardly fail but get a good number of well focused images that way. Then when you have more confidence, try it with one of the outer AF points so you can get better compositions without cropping. You could also have a go without the servo, as personally it drives me mad shunting around all the time like it does.
 
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dubcat said:
I am parallel - i have just cropped from one side of the test chart so you are just seeing perspective distortion from one half of the picture. I do now realise at least that microadjust has a minimal impact. I am sort of at my wits end to be honest. I see children photographers achieving almost magical focus which has eluded me completely. It's not just the odd miss.. it's every time. I have never used my lens at f/2.8 successfully ... about ready to give up. Still I should save myself a fortune in fast glass there is no point in buying :(
Click to expand...

Honestly I'm sure this is almost certainly simple technique. Don't be despondent - you'll crack it. Do as we've suggested and let's see some shots. Don't you know any photographers close to you who can help you out with this? :shrug:
 
CT i went to a meet and got some great tips - i don't think it is the way i am holding the camera in all honesty..

I will try ai servo and will try shooting more.. and see what happens. I don't seem to get misses with my 70-200 f4 in this way.. its just the 17-55 which is the lens i also happen to use the most.

Oh well.. I will give hoppy's advice a go. Something is odd anyway - in the lens chart test the camera seems to be backfocusing.. in my real world example it front focussed.. I guess it may be user error but i can't understand how after trying to get it right for so long. I will try the cereal box test (yup i have read all the threads on that hoppy) at some point ..

Thanks for taking the time to post though guys.
 
Dub just take a pic of anything in the room where you are now - use the pop up flash if you need to - Servo AF -centre AF point- and stick the shot up for us to have a look at. :)
 
CT thanks for sticking with me mate :) Feel much better now thanks to that. Ok here goes. Below are two pictures taken with servo af and using centre af point. There was no focus and recompose, i kept my finger on the focus button. The focus point was at the bottom of tiggers right eye where it meets his cheek - i.e. the eye on the left of the picture. It is dead centre in the third picture below basically.

The first shot is with 0 micro adjustment. The second is with +7 micro adjustment. The third is the whole frame shrunk down so you can get an idea of the actual scene (it happens to be of the +7MA capture).

Both pictures were ISO400 f/2.8 37mm at 1/200s. Image stabilisation was enabled on the lens as these shots were taken hand held. Given this was flash photography I do not believe camera shake here would have been a factor - i was also being VERY careful. In any case if there was enough ambient light exposing the picture (which there wasn't) I know 1/200s on a static subject would freeze it anyway.

tigger-MA-0.jpg

100% crop with 0 micro adjustment - ISO400 f/2.8 37mm 1/200s

tigger-MA-7.jpg

100% crop with +7 micro adjustment - ISO400 f/2.8 37mm 1/200s

akphoto-8843.jpg

complete frame with +7 micro adjustment - ISO400 f/2.8 37mm 1/200s

Seems that my camera/lens combo is benefiting from +7 micro adjust. Does this mean that without microadjustment it WAS front focusing? Wonder why this did not show up in the chart I took shots of earlier!
 
:clap:

+7 seems there or thereabouts. You can check and fine tune that later.

That's a good subject so have a go at a sequence, just for your own amusement. Keep that AF point nailed on the nearest eye and move closer/away, and move around it. Rattle off ten and just zoom in on them on the LCD to check. You'll prolly score 10/10 :thumbs:

NB Not surprised your AF chart was dodgy. That test is fundamentally flawed and also seems very prone to user-error too :thumbsdown:
 
I repeated the experiment with the camera mounted on a tripod and image stabilisation disabled on the lens. I took the following shots:

3 shots using live view magnified 10x and with 0 micro adjustment
3 shots using live view magnified 10x and with +7 micro adjustment
3 shots using regular viewfinder focussing with 0 micro adjustment
3 shots using regular viewfinder focussing with +7 micro adjustment

The results are similar to the above if not QUITE as dramatic.

I found that regardless of whether I had 0MA or +7MA when focussing with the live view x10 magnified (I was using the live view mode not the quick AF mode) the results were always sharp. This confused me - the micro adjustment seems to have no effect on live view mode.

The normal viewfinder based shooting results were consistent. The 0MA shots were not as sharp as the +7MA shots every time. I can share the results if you like. Let me know.

Dub
 
HoppyUK said:
:clap:

+7 seems there or thereabouts. You can check and fine tune that later.

That's a good subject so have a go at a sequence, just for your own amusement. Keep that AF point nailed on the nearest eye and move closer/away, and move around it. Rattle off ten and just zoom in on them on the LCD to check. You'll prolly score 10/10 :thumbs:

NB Not surprised your AF chart was dodgy. That test is fundamentally flawed and also seems very prone to user-error too :thumbsdown:
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Richard - in your opinion is the above a reasonable explanation for my misfocus in the picture of my daughter? I am thinking it is not :) The distance in the misfocus in my picture seems too great. Keen to hear your thoughts though.
 
All good :thumbs:

AF microadjust has no effect on live view. It's a different independent system that reads off the actual sensor - contrast-detect. Given a good target, live view AF can hardly be wrong and is extremely accurate. Normal AF uses a simulated image plane (phase-detect) which is the problem, but it's much faster.

I think the shot of your daughter is inconclusive. I don't think the +7 microadjust explains the error, and there are too many other potential variables going on.
 
HoppyUK said:
All good :thumbs:

AF microadjust has no effect on live view. It's a different independent system that reads off the actual sensor - contrast-detect. Given a good target, live view AF can hardly be wrong and is extremely accurate. Normal AF uses a simulated image plane (phase-detect) which is the problem, but it's much faster.

I think the shot of your daughter is inconclusive. I don't think the +7 microadjust explains the error, and there are too many other potential variables going on.
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As I thought :) Ok well at least I know that I have microadjusted it to my benefit now - that can't hurt. I will get cracking with some ai-servo centre focus points as suggested over the next few days and update this thread with my results.

I may still get my camera serviced at fixation - it needs a sensor clean and i may as well get the full monty while I am there.

Dub
 
I have a 17-55 on a 50D and have had problems with front focusing for the 10 months I've been using it. 90% of the time at 2.8 with 1-2m distance the eyes would be too soft for my liking.

I also found when using the lens to take pictures of my son rather than being in his face I would crop in slightly at 55mm. It was easy to spot then.

Finally after months of thinking it was technique I gave up living with it and sent it to fixation explaining my problems. They calibrated my lens and sent it back to me. It was front focusing.

Rattled off 20 various shots and the sharpness blew me away. It's far better than it was and tbh in the back of my mind I was a bit dissapointed for a £700 lens. Not anymore :)

I guess I could have played with it myself byt tbh it isn't something I was comfortable playing with, so as it was in warranty let the experts do it.
 
dannyjo22 said:
I have a 17-55 on a 50D and have had problems with front focusing for the 10 months I've been using it. 90% of the time at 2.8 with 1-2m distance the eyes would be too soft for my liking.

I also found when using the lens to take pictures of my son rather than being in his face I would crop in slightly at 55mm. It was easy to spot then.

Finally after months of thinking it was technique I gave up living with it and sent it to fixation explaining my problems. They calibrated my lens and sent it back to me. It was front focusing.

Rattled off 20 various shots and the sharpness blew me away. It's far better than it was and tbh in the back of my mind I was a bit dissapointed for a £700 lens. Not anymore :)

I guess I could have played with it myself byt tbh it isn't something I was comfortable playing with, so as it was in warranty let the experts do it.
Click to expand...

Popping in to Fixation at lunch time on Monday and will ask for an estimate. I will be without camera for a while though - didn't expect it would take so long! They told me it will be 2 days to get me an estimate and then another week after that to do any other work as they are doing a lot of Canon work right now. Hoping I get similar results to you :)
 
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