Manual focus sharper than autofocus

terryt

terryt

Suspended / Banned
Messages
538
Name
Terry
Edit My Images
Yes
I was testing a new lens I bought off a well known auction site over the weekend to see if it needed fine tuning. I tried the dot tune method but as its a zoom lens I found it difficult to find a mid point I was happy with at all focal lengths. Anyway, I'm happy with the lens but one thing I noticed after testing 2 lenses is that when using live view manual focus the image is alot sharper than using autofocus. I don't think this is a front/back focus issue, just that a much sharper image can be had from good manual focus compared to one that is seemingly perfectly autofocussed.

Does this sound right or is my dodgy eyesight better than my D7000 autofocus :thinking:
 
Either the lens is correctly focused, or it's not. Auto or manual makes no difference.
 
If the camera's AF was out or the lens was front/back focusing then manually focusing would remove these issues, hence giving a sharper image.
 
That was what I originally thought which was why I ended up using manual focus. I could adjust it so it would front focus and back focus but no matter what value I adjusted it to in between I was never able to get an image using AF as sharp as using MF (in liveview), and that was with 2 different lenses.

There's nothing wrong with the AF images, they are sharp, just not as sharp as MF at 100%
 
These modern auto-focus cameras are far from perfect.They have a flaw in that you just get stuck with what the auto-focus serves up and that's it.I have lots of issues with auto-focus.I wish my cameras were built and designed as manual focus cameras with the option of auto-focus instead of being built as auto focus cameras with manual focus as an option.:gag:
 
terryt said:
That was what I originally thought which was why I ended up using manual focus. I could adjust it so it would front focus and back focus but no matter what value I adjusted it to in between I was never able to get an image using AF as sharp as using MF (in liveview), and that was with 2 different lenses.

There's nothing wrong with the AF images, they are sharp, just not as sharp as MF at 100%
Click to expand...



This makes no sense. At some level of adjustment, it must achieve full focus, and when it does there will be no difference between that and fully focused using live view.

This has to be a problem with your AF technique. Are you using multiple AF targets or just a single one?
 
Single centre focus point on a tripod with remote focusing on a model robot. It could be the shutter speed as its been a bit gloomy but that still doesn't explain the difference using MF and AF.
 
Last edited:
No, it doesn't, but it simply cannot be the lens. Over what range did you try the AF fine tune? On mine, it goes from -20 to +20.
 
I tried the whole range -/+ 20. I'll try again on the weekend and will post pictures. Whats the best object to focus on? I know its best to use a focus chart to check for front/back focus but I prefer to use a real object to check for sharpness.
 
I would consider using a newspaper to focus on = lots of different sized fonts may help you decide

Les :thumbs:
 
terryt said:
I tried the whole range -/+ 20. I'll try again on the weekend and will post pictures. Whats the best object to focus on? I know its best to use a focus chart to check for front/back focus but I prefer to use a real object to check for sharpness.
Click to expand...

Seriously - use a chart.

Af points are quite big, you could (especially in low light) find the camera locks onto different parts of the object which will throw the results out.

Download a focus chart, print it on card at high quality (or paper, and tape to some card), and calibrate on that. Then check your calibration on an object to ensure you are happy :thumbs:
 
Last edited:
I would like to try this do you know a good place for a download chart?
 
kestral said:
These modern auto-focus cameras are far from perfect.They have a flaw in that you just get stuck with what the auto-focus serves up and that's it.I have lots of issues with auto-focus.I wish my cameras were built and designed as manual focus cameras with the option of auto-focus instead of being built as auto focus cameras with manual focus as an option.:gag:
Click to expand...

you don't half post some rubbish

for one thing modern AF is a lot more accurate than your eyesight and a lot quicker enabling it to lock onto and track moving subjects.

and for another if you want to use MF , it is a simple matter to flick the switch on the lens to MF and focus manually (although I only ever do with extreme macro , or whenthe light is too low - like using a 2xtc on an f5.6 lens - for the AF to work)
 
Thanks for the pointers, I was planning to use this chart but my printer ran out of ink :bonk:

Here's one of the shots done using MF but not one of the lenses I was testing for tuning. I was focusing on Danbo's head. Yes, I know it's not the most contrasty thing to focus on.
 
Last edited:
Is there a link to a concise instruction for checking focus?
Thanks
 
terryt said:
Thanks for the pointers, I was planning to use this chart but my printer ran out of ink :bonk:

Here's one of the shots done using MF but not one of the lenses I was testing for tuning. I was focusing on Danbo's head. Yes, I know it's not the most contrasty thing to focus on.
Click to expand...

You do not need anything special to check AF. In fact, those small angled targets posted all over the web are the bane of every camera service department. Target must be flat and square to the camera, and shot at a realistic shooting distance. If you don't do that, you may well find problems that don't exist normally, and when microadjust is reset it could be out at normal range.

Lots of threads on how to do AF-microadjust. Here's one from the other day, see post #5 http://www.talkphotography.co.uk/forums/showthread.php?t=482821
 
big soft moose said:
you don't half post some rubbish

for one thing modern AF is a lot more accurate than your eyesight and a lot quicker enabling it to lock onto and track moving subjects.

and for another if you want to use MF , it is a simple matter to flick the switch on the lens to MF and focus manually (although I only ever do with extreme macro , or whenthe light is too low - like using a 2xtc on an f5.6 lens - for the AF to work)
Click to expand...

Oh dear a lack of understanding and knowledge again.Someone who never used manual focus cameras with an f1.4 lens I take it. Do you have a 55 inch screen TV hanging on the wall by any chance.:lol:
 
kestral said:
Oh dear a lack of understanding and knowledge again.Someone who never used manual focus cameras with an f1.4 lens I take it. Do you have a 55 inch screen TV hanging on the wall by any chance.:lol:
Click to expand...

Actually I did - but I still have no idea what point you think you are making other than that you don't understand modern technology and subscribe to a fond view that things were 'better' back in the day

you can MF a modern DSLR if you really want - you can even get adaptors to use the old MF lenses (or buy modern MF lenses like those by Samyang

However you can't focus to the same degree of accuracy as quickly as a modern DSLR AF system , except in very low light, nor can you out perform tracking autofocus on a moving target
 
kestral said:
These modern auto-focus cameras are far from perfect.They have a flaw in that you just get stuck with what the auto-focus serves up and that's it.I have lots of issues with auto-focus.I wish my cameras were built and designed as manual focus cameras with the option of auto-focus instead of being built as auto focus cameras with manual focus as an option.:gag:
Click to expand...

big soft moose said:
you don't half post some rubbish

for one thing modern AF is a lot more accurate than your eyesight and a lot quicker enabling it to lock onto and track moving subjects.

and for another if you want to use MF , it is a simple matter to flick the switch on the lens to MF and focus manually (although I only ever do with extreme macro , or whenthe light is too low - like using a 2xtc on an f5.6 lens - for the AF to work)
Click to expand...

kestral said:
Oh dear a lack of understanding and knowledge again.Someone who never used manual focus cameras with an f1.4 lens I take it. Do you have a 55 inch screen TV hanging on the wall by any chance.:lol:
Click to expand...

I'm flabbergasted

I don't know of one modern DSLR that you can't select either manual or auto-focus (and then the further option of focus in live-view or the viewfinder).

What auto-focus 'serves up' is a focus on a surface that is supposed to be the same distance from the focal node as the sensor is. If that distance is different, then you will get 'the flaw' unless you can micro-adjust your camera to compensate for that difference. When you manual-focus through the viewfinder, you are not focussing on the sensor but on a bit of glass that is supposed to be the same distance from the focal node as the sensor is. If you manual or auto-focus in live-view, you are focussing on the sensor. If you manual or auto-focus without live-view, you are not focussing on the sensor.

Non-live-view focussing is typically 'phase-detection' which tends to be faster than plain 'contrast-detection (as used in live-view auto-focus) but because the focal plane is not the sensor, it relies on calibration to give a good result without back or front focus issues.

Although this is not perfect, I would argue that it isn't far from it and that for most DSLR users, autofocus gives better and faster results than manual focus in most situations.

Using manual focus with an f1.4 lens does not equip one with knowledge or understanding of auto-focus performance - it doesn't even equip the user with an understanding of manual focus (I started my photography with a film camera that you couldn't see any effect of adjusting the focus of the lens - you used the scale on the side of the focus ring and you guessed or measured the distance to the subject) - and none of this is affected by the size and placement of your television
 
Last edited:
kestral said:
These modern auto-focus cameras are far from perfect.They have a flaw in that you just get stuck with what the auto-focus serves up and that's it.I have lots of issues with auto-focus.I wish my cameras were built and designed as manual focus cameras with the option of auto-focus instead of being built as auto focus cameras with manual focus as an option.:gag:
Click to expand...

I think many people fall under the assumption that modern AF will do it's job regardless of what you point it at, but you as the picture taker still need to apply some judgement to get the best result. That said, I'd take an AF camera over a manual any day of the week for general use.

The one thing I do miss when I do switch over to manual focus is the split prism / micro prism focus aids; they worked brilliantly. I this what you mean by the camera being built as a manual focus camera?
 
big soft moose said:
you don't half post some rubbish

for one thing modern AF is a lot more accurate than your eyesight and a lot quicker enabling it to lock onto and track moving subjects.
Click to expand...

How on earth can you come up with such absolute claptrap. If you and I stood together and someone picked out a focussing target, my eyes would focus on said object long before your finger had ever got anywhere near the shutter button. In fact, the only possible scenario I can think of where your camera might stand a chance of beating my eyesight in a speed focussing contest is if I was p***ed.
 
Stuart M said:
How on earth can you come up with such absolute claptrap. If you and I stood together and someone picked out a focussing target, my eyes would focus on said object long before your finger had ever got anywhere near the shutter button. In fact, the only possible scenario I can think of where your camera might stand a chance of beating my eyesight in a speed focussing contest is if I was p***ed.
Click to expand...

And by missing the 2nd para you've managed to make it look like Pete was comparing AF to eyesight, whereas we all know he was comparing AF to eyesight and the hand eye coordination required to manually focus.
 
I didn't read it as such, Phil. As far as I am concerned, he was making two separate points, the first of which reads as though he actually believes that camera AF is quicker and more accurate than human eyesight.
 
If only a camera could match the human eye or focusing! The thing is, modern AF is very competant but it isn't infallible, it needs a decent target ie some texture or contrast, sometimes we have unrealistic expectations. Expecting a good focus in a dim night club with at f1.4 is going to be a hard task, that coupled with a very narrow DOF gives plenty of scope for error.
 
Stuart M said:
I didn't read it as such, Phil. As far as I am concerned, he was making two separate points, the first of which reads as though he actually believes that camera AF is quicker and more accurate than human eyesight.
Click to expand...

To MF you need to use your eye's :bonk:
Have you been chatting to my Mrs :thinking: she's very good at taking certain words out of a conversation and turning them around just for an argument :bonk:
 
There's no point in you giving it :bonk: Neil. The bloke made an inaccurate statement. I didn't alter it, I didn't doctor it; I simply quoted what he said in black & white. Anyone that makes such a bonkers statement deserves to be criticised for it.

And, no, I don't believe I've ever had the pleasure of chatting with your wife but I often do the same as she does. I often use sentences or passages from other people's writings to either agree with or criticise what they say ... in historical academic circles it's accepted practice and is commonly known as 'developing an argument'.
 
perhaps if you are having what you believe to be focusing issues have you tried spec savers it could well be you that is having the focus issues and not the camera age is a terrible thing
 
Stuart M said:
There's no point in you giving it :bonk: Neil. The bloke made an inaccurate statement. I didn't alter it, I didn't doctor it; I simply quoted what he said in black & white. Anyone that makes such a bonkers statement deserves to be criticised for it.

And, no, I don't believe I've ever had the pleasure of chatting with your wife but I often do the same as she does. I often use sentences or passages from other people's writings to either agree with or criticise what they say ... in historical academic circles it's accepted practice and is commonly known as 'developing an argument'.
Click to expand...

And selectively quoting on internet forums, for the sake of an argument is commonly known as 'trolling' and bears little or no resemblance to anything done in academic circles:thumbs:.

And you know that (surely because you appear to be quite intelligent), it's quite obvious to everyone reading that post that only quoting half of it changes the meaning of it immensely. Your eyes alone don't perform MF (which is the subject at hand) everyone knows that, why would you assume Pete is stupid?
 
Phil V said:
And selectively quoting on internet forums, for the sake of an argument is commonly known as 'trolling' and bears little or no resemblance to anything done in academic circles:thumbs:.

And you know that (surely because you appear to be quite intelligent), it's quite obvious to everyone reading that post that only quoting half of it changes the meaning of it immensely. Your eyes alone don't perform MF (which is the subject at hand) everyone knows that, why would you assume Pete is stupid?
Click to expand...

Stuart M said:
I agree.
Click to expand...

Nice to see, even if that second quote was taken somewhat out of context, buy hey, who cares about context. (source http://www.talkphotography.co.uk/forums/showthread.php?p=5307872#post5307872)
 
Phil V said:
And by missing the 2nd para you've managed to make it look like Pete was comparing AF to eyesight, whereas we all know he was comparing AF to eyesight and the hand eye coordination required to manually focus.
Click to expand...

Thanks phil - i'm not going to get into an argument with the guy, i can identify a troll when i see one , but I did of course mean that the AF locks on a lot more quickly than one can focus with MF by hand eye coordination.

Everyone knows that the human eye focuses dramatically fast, but this doesnt translate to the ability to roll a knurled focus ring to the right setting and keep the image of a moving object in focus manually.
 
Just got myself a D7000, it is sharper in live view than using the viewfinder:nuts:, had a play with the af fine tune and it needs -5 from a little testing I did, it actually then comes out a little sharper than live view, should I be concerned about this?
 
Ivan S said:
Just got myself a D7000, it is sharper in live view than using the viewfinder:nuts:, had a play with the af fine tune and it needs -5 from a little testing I did, it actually then comes out a little sharper than live view, should I be concerned about this?
Click to expand...

That is exactly what the af micro adjustment is for, there will always be tolerances in manufacturing and your adjusting for that.

If a lens can't get auto focus as accurate as manual focus after trying the full range of micro adjustment, then it was built out of tolerance and needs to go back to the manufacture.



As for the taking paragraphs out of context, somebody can alway make themselves look stupid if they wish, every knows what the topic is about, and plain common sense would have understood what was meant.
 
You must log in or register to reply here.
Back
Top