Manual Focus

[eternalforms]

A noob question here.  I recently bought the Nikon D90.  This is my first "real" camera.  I've used a few point and shoot cameras before, but they are very simple and almost entirely automated.  One thing I'm having a slight issue with is manual focus.  Many times, I'll frame up a shot and then focus in manually.  It looks good in the viewfinder.  I snap the photo.  It looks good on the camera view when I play it back.  But then, when I upload it to my computer and look at it in larger view, it is clearly NOT clear and sharp, but fuzzy.  Are there any specific tricks to manual focus, i.e. what point to focus on, etc.?  When I focus, I rotate the focus ring from fuzzy to clear to fuzzy and try to go back to where I think the sharpest focus is, but still having some issues.  Is this a practice thing?  Oh, and I wear glasses, so could that be causing the problem?  I try to get as close as I can to the viewfinder while wearing my glasses ...   

[stamper]

Do you have focus confirmation in the bottom left hand corner? The light will blink and when focus is confirmed then it will stop blinking and will be steady. A small round circle.

[eternalforms]

Well, this illustrates how little I know!  I didn't know about that little light.  I'll have to look for it! 

And I was just reading about adjusting the diopter for my nearsightedness so I could look through the viewfinder w/o my glasses.  Hopefully the +1.0 limit is enough for my eyes.  If not, I guess I can always get a different diopter ...

Think I'll look for the light first, though!

[eternalforms]

Fredjeang, you make some good points ... and I had to do some searching to figure out the difference between a zoom lens and a prime long focal lens.  : /  Noob at work.  Unfortunately, I have only the kit lens: 18-105mm as well as a 50mm.  Would it still be "harder" to go with the 18-105mm at full zoom and train with that? 

[Lost]

I don't think I have ever managed to focus any of my digital cameras reliably using the optical view finder. On my old film SLR, there was a nice focusing grid and split-line that made focus possible, but by DSLR does not have this.

However, manual focusing in live-view (on the back LCD) works really well. I routinely use MF for macro on my DSLR and old manual focus lenses on my GF1. As long as you can take the time to check the focus is spot on it works really well. At a pinch, I can focus using the printed distance scale on the lens with some of my older lenses, stopping the aperture down to increase depth of field (and crossing several fingers when pressing the shutter button!).

[lookit]

Autofocus is almost always more precise, provided that it is working (it will say when it isn't) and it is focusing on the right thing (generally something in the viewfinder will indicate the point of focus, which can be changed manually, or the correct point of focus can be approximated by autofocusing, reframing and shooting (not 100% perfect because lenses are generally made to focus across a plane, not a spherical surface, and by reframing the subject off-center you move it to a plane nearer than the distance you focused on, but generally good enough).

Manual focus (except by magnified live view, or guided by AF confirmation which is pointless for a lens that can be autofocused by motor) is not at all precise without a proper focusing screen -- those supplied with autofocus cameras (which are often not swappable) are optimized for brightness, not ease of focusing.

Since the light is basically scattered on the focusing screen, the refractive error caused by the need for glasses (or the glasses themselves) can make it hard to see the screen clearly to focus, but does not introduce focusing error.  There may be an adjustable diopter setting slider or wheel near the viewfinder to adjust it to your eyes for optimum sharpness of viewing.

[stamper]

Well, this illustrates how little I know!  I didn't know about that little light.  I'll have to look for it! 

And I was just reading about adjusting the diopter for my nearsightedness so I could look through the viewfinder w/o my glasses.  Hopefully the +1.0 limit is enough for my eyes.  If not, I guess I can always get a different diopter ...

Think I'll look for the light first, though!

My reply was aimed at Nikon cameras as the poster stated he has a D90. I noticed that some of the replies don't seem to take this into account and seem to wander into focusing in general rather than a Nikon camera.

[Ken Bennett]

The focusing screen is designed for a bright view, not accurate focusing. That means that the image may look in focus when it's really not. Kind of a pain, but the camera manufacturers assume you'll be using auto focus.

Try setting your AF to the rear thumb button (which I assume the D90 has. Hope so, anyway.) That de-couples focus from exposure, making it easier to use AF, then release the thumb button, recompose, and shoot away, without disturbing the focus.

You may be able to get a focusing screen that provides a more accurate view, but at the expense of being a lot darker. I have those in my Canon cameras, and they are great with the f/1.4 primes, okay with the f/2.8 zooms, and really dark with anything slower.

[Graystar]

Modern cameras are not meant to be manually focused, so they don't have split-circle focusing screens.  If you really want to focus manually (have no idea why) then you can purchase a split-circle focusing screen for $105 from KatzEye...

http://www.katzeyeoptics.com/item--Nikon-D80-D90-Focusing-Screen--prod_D80.html

The AF on my D90 was off slightly, causing all autofocused images to be off slightly.  I fixed it myself (I don't recommend it) and now the autofocus is very sharp.  If you're having a problem with focus accuracy then you probably should send the camera back to Nikon for an adjustment.  Switching to manual focus is definitely not a good solution.

[stamper]

Modern cameras are not meant to be manually focused, so they don't have split-circle focusing screens.  If you really want to focus manually (have no idea why) then you can purchase a split-circle focusing screen for $105 from KatzEye...

http://www.katzeyeoptics.com/item--Nikon-D80-D90-Focusing-Screen--prod_D80.html

The AF on my D90 was off slightly, causing all autofocused images to be off slightly.  I fixed it myself (I don't recommend it) and now the autofocus is very sharp.  If you're having a problem with focus accuracy then you probably should send the camera back to Nikon for an adjustment.  Switching to manual focus is definitely not a good solution.

I think an experienced photographer will take this with a pinch of salt. Are you trying to be provocative or are you not sure what you are talking about? Have you ever used a 10 stop ND filter? It can only be used with manual. I won't say any more for fear of offending you.

[Graystar]

I think an experienced photographer will take this with a pinch of salt. Are you trying to be provocative or are you not sure what you are talking about? Have you ever used a 10 stop ND filter? It can only be used with manual. I won't say any more for fear of offending you.

You're the one who's being provocative (more like being an ass, really.)  If you had read the opening post you would know that this is a new user with his first DSLR.  You would also know that his problem is with his attempt to manually focus *many* of his images.  If you had tried to use your brain you might have considered that quite possibly my answer was placed in this particular context, and was NOT a general diatribe on manual focus.  I have a very hard time believing that this noob is using a 10-stop ND filter on many of his images. 

That being said, he’s got a D90, which I also have.  AF works down to -1 EV, and I’m telling you right now...there is no way you’re going to manually focus at -1EV on a D90.  Not only has the meter stopped working (only works to 0 EV) but the viewfinder is nearly black.  It’s a great viewfinder...but it’s not THAT good.

Maybe you should work on keeping your responses within the context of what was asked, as well as the context of the equipment in question.  That way you won't come out looking like someone who has nothing better to do than pick a fight.

[stamper]

Quote

Modern cameras are not meant to be manually focused, so they don't have split-circle focusing screens. 

Unquote

This was the statement I was referring to. It is a ridiculous one in my opinion. I was the first to reply to the poster and gave him good advice which he acknowledged was something that he didn't know about. My reference about the 10 stop filter wasn't about the poster but about the need on a camera for manual focusing. It can only be used with manual focusing. I can't find anything in his post about -1EV so that wasn't an issue for him. You are the one who should reflect on attitudes and read up on manual focusing and modern cameras.

[Graystar]

“Modern cameras are not meant to be manually focused, so they don't have split-circle focusing screens.“

This was the statement I was referring to. It is a ridiculous one in my opinion.

But they aren’t.  If they were, they would have split circle focusing screens!

I was the first to reply to the poster and gave him good advice which he acknowledged was something that he didn't know about.

The focus indicator you’ve recommended comes from the AF system.  If you can get a green dot during manual focus, then you can autofocus.  Otherwise, you’re just as in the dark as the AF system.

My reference about the 10 stop filter wasn't about the poster but about the need on a camera for manual focusing. It can only be used with manual focusing. I can't find anything in his post about -1EV so that wasn't an issue for him.

My reference to -1EV, besides coming from the D90 manual, wasn’t about the poster but about your 10-stop ND filter reference.  As I said, the focus indicator comes from the AF system.  If you can’t focus with AF, then you won’t get a focus indicator.

You are the one who should reflect on attitudes and read up on manual focusing and modern cameras.

I have read up on manual focus on modern cameras as I was interested in the subject when I saw that cameras no longer came with split-circle focusing screens.  That’s how I focused my Canon F1 25 years ago so that’s what I was used to.  What I came to realize is that most of those articles are written by people who don’t understand autofocus.  It’s just like the old guys who say always use manual exposure, but then don’t know what exposure compensation does.  I’ve even read a webpage suggesting that manual focus was better for sports and action photography!  Talk about not wanting to let go!  But it *is* time to let go, and let technology give us a seriously helpful hand by letting the camera focus.

[stamper]

Quote

My reference to -1EV, besides coming from the D90 manual, wasn’t about the poster but about your 10-stop ND filter reference.  As I said, the focus indicator comes from the AF system.  If you can’t focus with AF, then you won’t get a focus indicator.

Unquote

As an owner of 4 Nikon DSLRS I can assure you that with manual focus you get a focus indicator when focus is manually acquired. I do not wish to fall out with you but you have this all wrong.

Quote

The focus indicator you’ve recommended comes from the AF system.  If you can get a green dot during manual focus, then you can autofocus.  Otherwise, you’re just as in the dark as the AF system.

Unquote

Simply not true

[Gary Brown]

Quote

My reference to -1EV, besides coming from the D90 manual, wasn’t about the poster but about your 10-stop ND filter reference.  As I said, the focus indicator comes from the AF system.  If you can’t focus with AF, then you won’t get a focus indicator.

Unquote

As an owner of 4 Nikon DSLRS I can assure you that with manual focus you get a focus indicator when focus is manually acquired. I do not wish to fall out with you but you have this all wrong.

Quote

The focus indicator you’ve recommended comes from the AF system.  If you can get a green dot during manual focus, then you can autofocus.  Otherwise, you’re just as in the dark as the AF system.

Unquote

Simply not true

The green dot comes from the autofocus system. As the manual explains in the "electronic range finder" explanation for manual focus:

"If the lens has a maximum aperture of f/5.6 or faster, the viewfinder focus indicator can be used to confirm whether the subject in the selected focus point is in focus (the focus point can be selected from any of the 51 focus points). After positioning the subject in the selected focus point, press the shutter release button halfway and rotate the lens focusing ring until the in-focus indicator is displayed." [Quoting the D300 manual, but same for other Nikon DSLRs.]

Basically, when using the green dot, you're using autofocus minus the focus motor — you still select an autofocus point and you're still dependent on the camera's autofocus system's ability to detect focus at that point (thus the aperture note and a later note that the green dot won't work in the same situations where autofocus won't work).

It's just that instead of the focus motor adjusting the lens, you adjust the lens; but you're still using the autofocus system if you use the green dot.

[Graystar]

"My reference to -1EV, besides coming from the D90 manual, wasn’t about the poster but about your 10-stop ND filter reference.  As I said, the focus indicator comes from the AF system.  If you can’t focus with AF, then you won’t get a focus indicator."

As an owner of 4 Nikon DSLRS I can assure you that with manual focus you get a focus indicator when focus is manually acquired. I do not wish to fall out with you but you have this all wrong.

"The focus indicator you’ve recommended comes from the AF system.  If you can get a green dot during manual focus, then you can autofocus.  Otherwise, you’re just as in the dark as the AF system."

Simply not true

Question posed to Nikon...
are there two different methods used to determine correct focus (one for manual and one for auto,) or is the same method used in both manual focus and autofocus?

Also, I have a D90. With regard to the question above, is a camera such as the D3 different in operation?

Here is my question put another way...if AF cannot get a focus lock, will manual focus mode give me a steady Focus Indicator?
The answer seems to be "No", and that both AF and manual focus use the same exact focus indication system. But I wanted to check.

Nikon’s response...
Hello [Graystar],

Thank you for contacting Nikon USA.
Yes, you are correct. The indicator will never be steady. It will always blink in both Manual and Auto focus. This applies to both cameras.

Hope this helps.

Regards,
Claribel C.


So, getting back to eternalforms and the focus problems.  As I was saying...modern cameras are not meant to be manually focus.  If the AF system can’t get a lock then you’re left guessing at focus by how the viewfinder looks.  So it is not a “practice thing”.  Also, it shouldn’t be your glasses.  If you adjusted the diopter correctly (see D90 manual, page 32) you will see the viewfinder as well as anyone (point the camera towards a bright white wall that’s out of focus when doing this.)

If you’re really hot to manually focus, then a split-circle focusing screen is needed, as I’ve already mentioned.  But really, manual focus doesn’t really get you anything.  AF-S lenses focus very quickly, and the D90 kit lens takes about 1/2 sec to go from infinity to 2 ft.  You’ve got multiple focus points, focus-&-recompose techniques involving focus lock and focus decoupling, focus assist lights...there are so many ways to get focused automatically that there’s just no benefit to manually focusing everything.  You paid a lot of money for this camera...make use of the technology in your hands.  It works.

That said...do not keep a camera that doesn’t autofocus accurately.  That’s a real problem.  Return and exchange the camera or send it to Nikon for repair.