Check your lenses!

Started 8 months ago | Discussions
Gerry Winterbourne
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Re: Great if you ever need to photograph a test
In reply to Colin Franks, 8 months ago

Colin Franks wrote:

darklamp wrote:

If a users doesn't have any reason to be displeased by their equipment they should leave it alone.

They should leave it alone? That's an odd perspective; why not run this free DIY test and then have the peace of mind knowing that one's kit is as dialed in as best as possible? I guess if one doesn't really care about their image quality, sure, just leave it as is.

The problem with testing focus on lenses is that the test is made at quite close range. Quite a few lenses change their focus characteristics as they change range, so it's quite possible that you might see an "error" in the test even though the lens focuses perfectly at different ranges or conditions. AF modules can be sensitive to light frequency (colour) so you must be careful about your test conditions. Aperture can sometimes have an effect ...

So now we need to consider what "error" actually means: does it mean inaccuracy under some artificial conditions rarely or ever met in practice? Or does it mean a visible inaccuracy in real world use? What darklamp is implying is that it's the second possibility that really matters.

So, yes "should" leave it alone is the correct response. I guess if one doesn't really care about their image quality, sure, play with artificial conditions rather than judging real photos.  That is, if you care about image quality, study images and not tests.

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meland
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Re: Great if you ever need to photograph a test
In reply to Colin Franks, 8 months ago

Colin Franks wrote:

It's interesting to witness such rigidity. Cheese and Rice, we're not talking about taking your lens apart, it's a simple, free test to see if ones lens is focusing properly! You make a simple adjustment which is.....for some strange reason....already in your camera (those stupid engineers) and that's it. If it turns out that it's correct, then great; but if turns out that it could use adjustment (like mine really did), all the better.

Originally MFA was put into certain professional DSLRs because under the arduous conditions some photographers (sports, photojournalists, wildlife) put their equipment through, with little easy access to a service department, it enabled them to make emergency adjustments in the field.

Once amateurs heard that results could sometimes be improved by calibration (especially through forums like this) some of them began sending their equipment in on a regular basis.  Now this is quite a time consuming operation for any service department and unfortunately if you calibrate lens A to body B there is no guarantee that it will retain its calibration for Body C.

So after much debate it was decided to put MFA as a software feature into certain bodies.  Some engineers resisted it because they knew that if you give some people a chance to fiddle they will - and sometimes make things worse.

You should realise that MFA only works for a particular distance.  Get it 'right' for, say, 10ft and you might find infinity focus, or focus at 3ft gets worse.

Now some people love fiddling (or should I be kind and say fine tuning) and if you are one of those then great, go ahead.

But if you're not, then unless you really notice a problem might I suggest you leave well alone and save yourself some grief.

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EinsteinsGhost
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Remember what you say...
In reply to darklamp, 8 months ago

Why are you opposed to the ability ti correct ?

I've explained at some length what I think of micro focus adjustment and in particular that it's not something beginners should be encouraged to do ( in fact they should be discouraged until they've developed more knowledge ).

I did not, however, say that I oppose the feature completely, and I would like you to stop misrepresenting what I say.

The thread is about usefulness of AF micro adjustment, which you attempted to downplay. This can only come across as something you don't believe in. Or, do you?

This is something that ALL should be aware of. I see no reason for beginners to be ignorant about it. In fact, they are better off when they can learn that a missed focus might not necessarily be their own fault.

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EinsteinsGhost
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In reply to JF69, 8 months ago

EinsteinsGhost wrote:

If you can't see it but I can, it makes sense for me to go fix it. And a small difference can also be a nuisance at longer distances. Why are you opposed to the ability ti correct?

If precision is not important, then a lot we claim to want becomes unwarranted.

And as an engineer, I believe in accuracy and ability to fix inaccuracies, rather than wait and either scramble or simply ignore an issue.

I call your FUD; you left the rational discussion table when you wrote "Why are you opposed to the abililty ti(o) correct?"

Stop spreading unnecessary FUD & BS, & read posts/replies before yours before participating in any thread or forum, it's basic manners so as not to waste space & other people's time: my post addresses the issues we're dicussing, read it.

And how well tou fit in. Hypocrisy too. All this nonsense provides a good illustration to how people shouldn't "discuss".

Now, back to the topic... why is it a terrible thing to have the feature and use it when needed? Answer here, not somewhere in the cloud.

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Forrest
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In reply to Colin Franks, 8 months ago

Colin Franks wrote:

It's interesting to witness such rigidity. Cheese and Rice, we're not talking about taking your lens apart, it's a simple, free test to see if ones lens is focusing properly! You make a simple adjustment which is.....for some strange reason....already in your camera (those stupid engineers) and that's it. If it turns out that it's correct, then great; but if turns out that it could use adjustment (like mine really did), all the better.

.

You replied to my post but your reply is unrelated to anything I said.

There's no reason to post an image of text, when you can just post text.

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darklamp
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Re: Remember what you say...
In reply to EinsteinsGhost, 8 months ago

they are better off when they can learn that a missed focus might not necessarily be their own fault.

Beginners will, in my experience, believe even the wildest fantasy if it means they can blame the equipment and not themselves.  They don't need any encouragement to believe this at all.  It's sheer bloody murder convincing some of them that they could be in any way at fault.

That's the whole point. Beginner's think they can "adjust" their way out of problems which are just normal focusing errors. I've see beginners trying to use micro focus adjustment to fix focus when the camera was on auto focus point select and simply did what it was told it could - pick any focus point anywhere in frame, But what did the beginner do ? Blame the camera, the the lens was faulty, then it was the AF system in the camera, then the calibration didn't match and we were down to adjusting micro focus settings.  Then they sold the camera and the whole thing started again.

So beginners, IMO, are better off not having or knowing anything about micro focus adjustment until they learn the core elements of their AF system and how to use it properly.

And, let's remember, AF is NOT perfect. It is not designed to be perfect. It's intended only as an aid to focus. If you want perfect focus, use manual focus.

That's why you'll often see lens reviewers commenting positively on lenses that have full time manual focus capability.

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EinsteinsGhost
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In reply to darklamp, 8 months ago

Beginners ought to be aware of back/front focus issues and while entry level bodies generally don't allow fixing the issue (don't tell me that is a good thing, for anybody), it is another piece of information they can watch for.

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Cane
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Re: Check your lenses!
In reply to Colin Franks, 8 months ago

Colin Franks wrote:

Clueless Wanderer wrote:

Hmm... Never had an issue with lens or camera body AF ..maybe I have been lucky.

You don't really know until you do the proper test. As there is an "acceptable range" of any new lens to be within, a person's new lens could very well be out by a little.

http://www.youtube.com/watch?v=52fBIp4BI84

You can download the pdf to print off, and make your own tool here:

http://petapixel.com/2013/03/12/ghettoca-a-diy-lens-calibration-tool-for-micro-adjustment-enabled-dslrs/

Is there any way to mount one of these tools to a cat? I know there are quit a few cats in here that will feel left out if they aren't involved in camera equipment testing.

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jackdan
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Re: Great if you ever need to photograph a test
In reply to Gerry Winterbourne, 8 months ago

Gerry Winterbourne wrote:

Colin Franks wrote:

darklamp wrote:

If a users doesn't have any reason to be displeased by their equipment they should leave it alone.

They should leave it alone? That's an odd perspective; why not run this free DIY test and then have the peace of mind knowing that one's kit is as dialed in as best as possible? I guess if one doesn't really care about their image quality, sure, just leave it as is.

The problem with testing focus on lenses is that the test is made at quite close range. Quite a few lenses change their focus characteristics as they change range, so it's quite possible that you might see an "error" in the test even though the lens focuses perfectly at different ranges or conditions. AF modules can be sensitive to light frequency (colour) so you must be careful about your test conditions. Aperture can sometimes have an effect ...

So now we need to consider what "error" actually means: does it mean inaccuracy under some artificial conditions rarely or ever met in practice? Or does it mean a visible inaccuracy in real world use? What darklamp is implying is that it's the second possibility that really matters.

So, yes "should" leave it alone is the correct response. I guess if one doesn't really care about their image quality, sure, play with artificial conditions rather than judging real photos. That is, if you care about image quality, study images and not tests.

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Gerry
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Well said. On these forums there is a lot of well meaning, but unqualified people, offering advice. Buyer beware.

I would say anyone that says to adjust a camera's focus without offering the warning that the calibration applies only to a specific focal length for zooms and for a specific camera to subject distance and whatever other variables come into play is not qualified to be giving the advice. I don't fault them for trying to be helpful, though. They just don't know any better.

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JF69
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Did it, found your name there ;)
In reply to EinsteinsGhost, 8 months ago

EinsteinsGhost wrote:

EinsteinsGhost wrote:

If you can't see it but I can, it makes sense for me to go fix it. And a small difference can also be a nuisance at longer distances. Why are you opposed to the ability ti correct?

If precision is not important, then a lot we claim to want becomes unwarranted.

And as an engineer, I believe in accuracy and ability to fix inaccuracies, rather than wait and either scramble or simply ignore an issue.

I call your FUD; you left the rational discussion table when you wrote "Why are you opposed to the abililty ti(o) correct?"

Stop spreading unnecessary FUD & BS, & read posts/replies before yours before participating in any thread or forum, it's basic manners so as not to waste space & other people's time: my post addresses the issues we're dicussing, read it.

And how well tou fit in. Hypocrisy too. All this nonsense provides a good illustration to how people shouldn't "discuss".

Now, back to the topic... why is it a terrible thing to have the feature and use it when needed? Answer here, not somewhere in the cloud.

Read the posts, don't be lazy.

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Doss
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Ability to calibrate is important, but miscalibration with test charts may result.
In reply to Gerry Winterbourne, 8 months ago

Gerry Winterbourne wrote:

The problem with testing focus on lenses is that the test is made at quite close range. Quite a few lenses change their focus characteristics as they change range, so it's quite possible that you might see an "error" in the test even though the lens focuses perfectly at different ranges or conditions. AF modules can be sensitive to light frequency (colour) so you must be careful about your test conditions. Aperture can sometimes have an effect ...

Glad to read someone has made this important point. It's sound advice.

On the other hand, certain lenses with certain cameras can be consistently out. From experience I can tell you some older Nikon AF lenses horrendously back focus on FF dSLRs, so the need to have the ability to adjust is paramount.

I think it's also worth pointing out that all SLRs (all that I have ever come across) can have focus adjusted mechanically, usually with a micro-screwdriver or allen key under the mirror. This is sometimes necessary due to either manufacturing error or a heavy knock. However, this effects all lenses in both auto and manual focusing.

Be it AF fine tune or mechanical: Adjust with caution and prior knowledge.

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Gerry Winterbourne
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Re: Remember what you say...
In reply to EinsteinsGhost, 8 months ago

EinsteinsGhost wrote:

Why are you opposed to the ability ti correct ?

I've explained at some length what I think of micro focus adjustment and in particular that it's not something beginners should be encouraged to do ( in fact they should be discouraged until they've developed more knowledge ).

I did not, however, say that I oppose the feature completely, and I would like you to stop misrepresenting what I say.

The thread is about usefulness of AF micro adjustment, which you attempted to downplay. This can only come across as something you don't believe in. Or, do you?

The OP is promoting MFA as something to do on the basis of a test that is quick and simple. However, what the OP doesn't say - because he doesn't understand all the factors - is that the test is actually not very reliable.

darklamp is saying that doing MFA just on the basis of this test is quite likely to make things worse rather than better, and is therefore something to avoid unless other evidence (such as real pictures that are badly focused) shows a problem.

Although you say "The thread is about usefulness of AF micro adjustment" it isn't.  It's true it started that way but it's actually about the usefulness of a test, whose purpose is to see if MFA is needed.  There is nothing in what darklamp has written to say that he doesn't "believe in" MFA; what he doesn't believe in is unjustified MFA on the basis of a flawed test.

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Gerry
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darklamp
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Chill y'all
In reply to Gerry Winterbourne, 8 months ago

Some people think that beginners should be doing MFA.  I just think it's a recipe for tears before bedtime for beginners and that's just me reporting what I've see happen with many people.

I've expressed that as clearly as possible and I don't care if any particular person does or does not use MFA- it's your camera and it's not going to bother me one way or another if you do or don't.

Why people are taking this generic cautionary advice as an attack on their personal rights and freedoms I don't know.  Every post that doesn't agree with y'all isn't a personal attack.

So please, Chill.

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Gerry Winterbourne
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Re: Chill y'all
In reply to darklamp, 8 months ago

darklamp wrote:

Are you reading in threaded or flat view?  It looks as if this post was addressed to EinsteinsGhost, not me - at least, I hope so.

Some people think that beginners should be doing MFA. I just think it's a recipe for tears before bedtime for beginners and that's just me reporting what I've see happen with many people.

I've expressed that as clearly as possible and I don't care if any particular person does or does not use MFA- it's your camera and it's not going to bother me one way or another if you do or don't.

Why people are taking this generic cautionary advice as an attack on their personal rights and freedoms I don't know. Every post that doesn't agree with y'all isn't a personal attack.

So please, Chill.

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Gerry
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tcg550
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Re: Great if you ever need to photograph a test
In reply to Colin Franks, 8 months ago

Colin Franks wrote:

It's interesting to witness such rigidity. Cheese and Rice, we're not talking about taking your lens apart, it's a simple, free test to see if ones lens is focusing properly! You make a simple adjustment which is.....for some strange reason....already in your camera (those stupid engineers) and that's it. If it turns out that it's correct, then great; but if turns out that it could use adjustment (like mine really did), all the better.

But you said you didn't know you had a problem until you checked. Were your photos in focus before the test? If the test was not available would you have even suspected you had a n issue?

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darklamp
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Addressed to everyone ( including me ) (nt)
In reply to Gerry Winterbourne, 8 months ago
No text.
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Colin Franks
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Re: Great if you ever need to photograph a test
In reply to tcg550, 8 months ago

tcg550 wrote:

But you said you didn't know you had a problem until you checked. Were your photos in focus before the test? If the test was not available would you have even suspected you had a n issue?

No, I didn't know I had a problem until I checked, but suspected.  I had done precious little shooting with the 50mm (I've only had it a short while), but I did have a few images at 1.2 that didn't seem to be focused where I had focused, so started looking into it, which lead me to the many various articles and YouTube videos showing this easy, reversible procedure.

I appreciate the comments about how making these adjustments at a particular distance away from the lens may be deleterious at other distances when shooting, but that makes me curious about why all of the tutorials say to do it at 5-10 times the focal range. Where did they get that from, and is it possibly correct?  I remember finding one YT video where the guy said to set it up at 50 times the focal range of the lens; that clearly was erroneous, or was it?

I may also re-do this test in different lighting (if the sun ever comes out again).  

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darklamp
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The internet
In reply to Colin Franks, 8 months ago

Where did they get that from

Alas people on the internet seem to have no conscience at all about making statements they just made up without bothering with anything as boring as checking they're true.  I could mention at least one oft quoted photography website where the owner can be shown to have posted completely self-contradictory statements about particular pieces of equipment.  It's there to drive people to the website, not help them.

Likewise, many people seem to repeat the first thing google finds and repeat it as if it was bound to be true.  And people seems to confuse something been said often with the truth, when the truth is often drowned out by people repeating the inaccuracy.

One advantage of these forums is that after a time you get to work out for yourself who's a reliable source and who's stuff you should triple check ( you should double check everyone ).

Generalizations about lenses are not easy to make which are not trivial.  Every design has it's own nuances.  Unfortunately people like generalizations.

So let's be careful out there.

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Skipper494
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Re: Check your lenses!
In reply to Clueless Wanderer, 8 months ago

Me, neither.

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meland
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Re: Great if you ever need to photograph a test
In reply to Colin Franks, 8 months ago

Colin Franks wrote:

tcg550 wrote:

But you said you didn't know you had a problem until you checked. Were your photos in focus before the test? If the test was not available would you have even suspected you had a n issue?

No, I didn't know I had a problem until I checked, but suspected. I had done precious little shooting with the 50mm (I've only had it a short while), but I did have a few images at 1.2 that didn't seem to be focused where I had focused, so started looking into it, which lead me to the many various articles and YouTube videos showing this easy, reversible procedure.

I appreciate the comments about how making these adjustments at a particular distance away from the lens may be deleterious at other distances when shooting, but that makes me curious about why all of the tutorials say to do it at 5-10 times the focal range. Where did they get that from, and is it possibly correct? I remember finding one YT video where the guy said to set it up at 50 times the focal range of the lens; that clearly was erroneous, or was it?

I may also re-do this test in different lighting (if the sun ever comes out again).

Canon themselves recommend to check and adjust at 50x the focal length. For the average person this is impossible for the longer focal lengths, unless you do it outside, so people have adapted the test to shorter distances.

In practice, if you are going to do this adjustment, it makes sense to do it at the working distances you would commonly shoot at for the focal length in question.

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