Autofocus/Lens Problem?

htid

htid

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Chris
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Hi,

I have a Nikon d7000 with Nikon 1.4tc and Nikon 300mm f4. The quality used to be pin sharp, but recently I've been finding that I can't see to get any super sharp shots! I'm not sure if there's something wrong with the lens and I wonder what you guys think. Here's an example from Brownsea Island last week - I haven't got a single sharp shot out of 100s even though the weather was brilliant. The following, as you can see, is ISO 250, 1000th/s...surely at such low ISOs and with a fast shutter speed, with the focus point directly on the head, it should be sharper than this? I'm very annoyed that during the whole time I've spent there, not one shot is 100% sharp. Is there any way to fix this? Sorry it's so huge, just wanted to show it at 100% zoom.



Thanks!
 
Was this much of a crop?

You were shooting wide open at f5.6, although it should be sharp wide open.

It could be atmospheric turbulence (heat haze), especially as the weather was good, and if this was shot at distance and cropped.
 
Are you sure that that was the focus point? To me it looks like the water ripple, just at the bottom of the shot where it has been cropped (by the front foot) is sharp. Possible front focusing?
 
That's just 'actual pixels' in photoshop, so it shouldn't matter the crop should it, it should be sharp at that size? Either way, it's a crop but not huge..will have to post the original up tomorrow. It looked really sharp through the viewfinder so I would suspect heat haze isn't the cause...not sure if I'm right in thinking that though.

Ploddles, that's what Nikons own NX2 shows as the focus point, so I'm assuming it is correct. Not sure what front focusing is, I'll have a read.
 
You can get front or back focusing and some cameras have micro adjustment as a menu option to enable you to overcome it.

Also, was it autofocus or manual? If manual is your viewfinder diopter set correctly for your eye.
 
htid said:
It looked really sharp through the viewfinder so I would suspect heat haze isn't the cause...not sure if I'm right in thinking that though.
Click to expand...

The longer the focal length the greater the chance of it spoiling the image, I rarely see it through the viewfinder, but will see it in the shot.

It does not need to be hot for this to become a problem, if the ground is warmer than the air, the heat will rise and cause the turbulence.

It certainly looks like it is the problem with your image, I would be inclined to do a couple of controlled tests in the house or garden with and without the TC just to confirm if there is an issue with the kit.
 
Hi Chris

Feel your pain here, but if you are going to look at 100% crops from an 18MP sensor then pain is the most likely result :D

I too expected my pictures to be zoomable (is that a word?) with so many MP but it very rarely works like that even with the best glass.

Have you tested the lens to check it's not at fault, tripod, IS/VR off, live view focus etc?

Could you post up some images you were happy with the sharpness of??

David
 
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htid said:
That's just 'actual pixels' in photoshop, so it shouldn't matter the crop should it, it should be sharp at that size? Either way, it's a crop but not huge..will have to post the original up tomorrow. It looked really sharp through the viewfinder so I would suspect heat haze isn't the cause...not sure if I'm right in thinking that though.

Ploddles, that's what Nikons own NX2 shows as the focus point, so I'm assuming it is correct. Not sure what front focusing is, I'll have a read.
Click to expand...

NX2 knows which focus point you used - as in that fp is x pixels in from the left and y pixels down from the top in the original frame - but if you crop the image it assumes the fp is still in the same place pixel-wise.

You can test this by taking an image where the fp is in the centre and then cropping - the fp NX2 shows will then be in the centre of the cropped image.
 
Yep I plan to tonight :) Thanks for all the info so far!
 
If you're shooting with a TC, you're better off stopping down a bit.

TCs degrade the image especially wide open and at f5.6 you're as wide as you can be with a 1.4x TC/f4 lens combination. Try shooting after dialing in at least f6ish and upping the ISO a notch or two if you want to keep 1/1000s SS.
 
chromatin64 said:
If you're shooting with a TC, you're better off stopping down a bit.

TCs degrade the image especially wide open and at f5.6 you're as wide as you can be with a 1.4x TC/f4 lens combination. Try shooting after dialing in at least f6ish and upping the ISO a notch or two if you want to keep 1/1000s SS.
Click to expand...

I have the same lens, and have no problems using it wide open with the 1.4 or 1.7TC however in general your point is valid, and if possible I do try and use f7.1 whenever possible.
 


This is the original uncropped version. I've always used f5.6 and been happy with the results before (even at 100% zoom), but it's over the last month or two that I've noticed the problem. The original wasn't an actual crop, so that was definitely the focus point. I just went to 100% and did a screenshot so the focus point hadn't moved in NX2.

I'll try and do some controlled tests and see what the results are. If it's heat haze then I guess there's nothnig that can be done, it's just so annoying to go all the way to Brownsea and get no great sharp shots :/
 
htid said:
I'll try and do some controlled tests and see what the results are. If it's heat haze then I guess there's nothnig that can be done, it's just so annoying to go all the way to Brownsea and get no great sharp shots :/
Click to expand...

Looks fine until you crop it, I am sure it is air turbulence causing it, here a couple of mine from February and March a couple of years ago, the first looked fine through the viewfinder, the second it was so bad I could see the effect through the viewfinder, bear in mind I am shooting 700mm and the longer focal length increases the effect.

At least you had not lugged a 500mm a couple of miles to be disappointed :D

173_057.jpg


176_048.jpg
 
At full size it looks fine to me.

Too many people 'pixel peep' and are then disappointed. By all means crop it but don't pixel peep.
 
Viewing it at 100% isn't pixel peeping imo ;) I've taken many photos before where if I view at 100% it still looks perfectly fine. This was also a crop to 100% and look how sharp the eyes are. I reckon it must be heat haze as Martyn said.

 
looks like front focus water ripples sharp.
 
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