Another Stupid Question

[zutty]

Well here I go again. Some times when I'm using manual focus, which is a lot these days, The photo just doesn't seem as tack sharp as I thought it was in the viewfinder. This is with my new 24-70 2.8 with my D7100. I never adjusted the diopter and am wondering how this is done and if I'm being neurotic (a good possibility)
or not. Here's an example of this that I shot today. Thanks for all your patience.

 

[Just-Clayton]

What were your settings?? It looks like your f-stop was wide open to get the shot. That means if you set your f-stop at 2.8, the rose has a narrow depth of focus and everything else will be blurry or soft.

 

[FastGlass]

Setting the diopter is pretty easy. Focus on something and rotate the diopter knob untill you see it as sharp. Keep in mind that when putting the focus point on something in the view finder and focusing on that, the diopter adjustment has nothing to do to fix focus issues the camera has. You should also check to see if your lense is front or back focusing.

 

[DraganDL]

Do you rely on a focus confirmation dot?

 

[John P]

What aperature setting?

 

[singlerosa_RIP]

Here's another stupid question. Why are you putting the 24-70 on a DX body when you have a D800?

 

[zutty]

Yes, that photo was at 2.8. I was trying to get the shadow to be soft. Here is one at f18 and shutter speed of 1/13. I focused manually in both, trying to use the closest red rose as my focus point. I try to rely on my eyes more than the dot for focus, but I do glance at it when it's close. I was using the D7100 because I am letting my nephew use the D800 for an important shoot he has. I'll have it back thurs. and then I'll try again with that.

 

[aroy]

Check the sharpness of focus
. If you have a scale, then prop it up at an angle of 45 degrees (approx). The top away from you, the bottom towards you,
. Put the camera on the tripod, and level it so that the centre of the lense is around the middle.
. Use the largest aperture, f2.8 in your case.
. Focus the camera on a full graduation, say 6 inches or 15 cm graduation. It is best to adjust the camera so that it is level.
. Now shoot.

You can also verify AF similarly.

. Load the image in computer and examine the sharpness of graduations.
. If the graduation you focused on is the sharpest, then your focus is perfect.
. If the graduation above the mark is sharpest, then you are focusing is at the back.
. If the graduation below the mark is sharpest, then you are focusing is at the front.

For AF adjust the AF fine tune for this lense. The amount can be found on the net.
For MF, adjust the Diopter wheel; which is on the eye piece, and try a few times till you get it right.

NOTE that if your eyes/glasses are outside the range of the diopter adjuster, then you will never get perfect focus in MF. In that case an additional diopter corrected eyepiece is required. some thing like this
DK-20C -2.0 Correction Eyepiece from Nikon

I have the same problem and with my glasses the diopter correction is just out side the range, so where I find the sharpest focus, is way off.

 

[Marcel]

I find it very difficult if not almost impossible to focus manually with the focusing screens that come with the DSLRs. I've replaced all my ground glasses from my D700, 600 and 7000 just to have a better surface to manually focus on. The focusing screen that comes standard are just too transparent to do a good job of manual focus. You can see THROUGH them, but when you try focusing it gets more difficult, specially with wider aperture lenses. The only way to focus accurately with these lenses is to use "LiveView" of the camera and zoom in to focus. This can be done for non moving subjects, but becomes impossible when shooting people.

So you can try all you want, but the only way to be certain is with Liveview. Of course, you can also use the LiveView to compare your manual focusing when the camera is on a tripod and the subject is still.

To adjust the diopter, you must just use the lines in the viewfinder and make them sharp. Instructions are in the user manual.

 

[yauman]

I never adjusted the diopter and am wondering how this is done and if I'm being neurotic (a good possibility)
or not.

Hmm.. wait if you never adjusted the diopter settings how does anything in the viewfinder - the information at the bottom of the viewfinder screen - look clear? You must have really good eyesight! That's the first thing I do whenever I use any camera - even when I'm handed a DSLR to shoot for a someone, I have to adjust the diopter otherwise everything is blurred! It's really quick and easy - it's the little knob next to the viewfinder - just don't poke your eyeballs out when you do

 

[zutty]

Thanks for the helpful advice all!

 

[zutty]

Setting the diopter is pretty easy. Focus on something and rotate the diopter knob untill you see it as sharp. Keep in mind that when putting the focus point on something in the view finder and focusing on that, the diopter adjustment has nothing to do to fix focus issues the camera has. You should also check to see if your lense is front or back focusing.

I'm not sure how to determine if a lens is back or front focusing. Is it that certain lenses are just that way or is it individual lenses, and I'm not sure what that really means. Please pardon my ignorance..

 

[aroy]

I'm not sure how to determine if a lens is back or front focusing. Is it that certain lenses are just that way or is it individual lenses, and I'm not sure what that really means. Please pardon my ignorance..

It is an individual lense and camera combination.

The back/front focusing is when the Auto Focus focuses behind/ahead of where it is supposed to focus. This is mainly a camera-lense combination problem. The lense servo may be maladjusted so that it sets the lense focus away from where it was supposed to be. Most high end cameras have a facility to enter a number (+ or -) which shifts the focus. In low end camera it is not there.

You take a shot of an inclined scale (with the top away from you and the bottom towards you) and focus at a graduation, say XXX. If there is back focus, then the graduations above XXX will be in focus, if there is a front focus then the graduation below will be in focus. The job of the fine tuning of focus in camera is to shift the focus (in the lense) to compensate for this error. What number to dial is explained on the net in details (Lens Align is one such product which has extensive details on its site).

Ultimately for critical focus, as in Macro, it is best to use manual focus for the fine tuning. The AF is pretty coarse and when the object is small and angular, it may not know where exactly you want the focus to be.