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toriaj
11-20-2006, 10:12 PM
Why couldn't I get this in focus?

17477

It was a night shot. I used a tripod, with a self-timer delay of 10 seconds. There was no wind.

Granted, it was at 240 mm. Over a block away. And I wasn't able to manually focus it any better. Is this just an impossible shot (at least with the $200 Sigma?)

Here is (I think) a 100% crop of the focus point:

17478

Any suggestions?
Here's the EXIF: (I must have left the -1.7 EV on from the last set of shots)
Nikon D50
2006/11/19 19:59:57.7
JPEG (8-bit) Fine
Image Size: Large (2000 x 3008)
Lens: 70-300mm F/4-5.6 D
Focal Length: 240mm
Exposure Mode: Aperture Priority
Metering Mode: Spot
1/2 sec - F/5.3
Exposure Comp.: -1.7 EV
Sensitivity: ISO 200
Optimize Image: Normal
White Balance: Incandescent
AF Mode: AF-S
Flash Sync Mode: Not Attached
Auto Flash Comp: 0 EV
Color Mode: Mode IIIa (sRGB)
Tone Comp.: Auto
Hue Adjustment: 0°
Saturation: Normal
Sharpening: Auto
Image Comment:
Long Exposure NR: Off

Prospero
11-27-2006, 11:52 AM
I am not sure, but it might not be autofocus failure. I see that you used a shutterspeed of half a second. At that speed you can experience vibrations caused by the mirror. For that reason some cameras (sadly not the D50) have mirror lock-up. This raises the mirror well before taking a picture, which prevents these vibrations.

On the other hand, the Sigma's autofocus is not all that accurate in low light situations due to its small maximum apperture (this allows less light to enter the camera making autofocussing more difficult).

toriaj
11-27-2006, 08:55 PM
Okay, that makes sense. Thanks!

SpecialK
12-07-2006, 06:46 PM
I infer from your comment that you also tried to manually focus the shot which was no sharper. That would rule out the autofocus-problem answer.

I have that lens, which I like and has generally good reviews. I have not yet used it in that low of light.

I would try going to a longer shutter time, say 2 seconds or something, which would minimize any initial vibration from the mirror.

However, the photo did not really seem "shaky", so frankly, I don't have the exact answer, sorry :-(

toriaj
12-07-2006, 09:13 PM
Thanks for your reply, SpecialK. I think I was really stretching the capabilities of the lens :o And if I couldn't even focus it, what could I expect? Like you, I have really enjoyed the lens. I think my next purchase will be a prime lens, "primarily" for low light shots ... (sorry, that was horrible :eek: )

Clyde
12-08-2006, 03:53 PM
Why couldn't I get this in focus?
Lens: 70-300mm F/4-5.6 D

1/2 sec - F/5.3

I'm betting 5.3 is wide open. It would probably be sharper at a smaller aperture, which would also give you a wider DOF. Consider that the narrower the DOF, the smaller the range of things that will appear in focus (a definition of DOF.) So, the smaller the aperture, the more tolerance you have for focusing error. Since you are already at 1/2 sec, why not try at 2 sec, and f/7.1? Maybe even up your ISO to 400, and try 2 sec and f/8?

Just some thoughts...

Clyde

toriaj
12-08-2006, 09:00 PM
Okay, thank you. I hadn't considered aperture change for this shot. Makes sense though! I'll use that next time this comes up.

SpecialK
12-09-2006, 04:27 PM
If you combine the 2 suggestions (longer shutter, smaller aperture - which goes together anyway), I think you'll have a better result. Oh, and zero your exposure compensation :-)

While stopping down a couple stops from the maximum aperture generally is the sweet-spot of lens performance, I doubt that your lens is so poor near maximum that you can't get a much sharper shot than in your sample. It should not be that dramatic an improvement.

However, as far the depth of field increase goes, it will not help on a "flat" subject like the front of a church. It only extends the front-to-back range of what we call acceptable sharp focus. On a 2-dimensional subject like your church, there is no depth by definition. If it's mis-focused, DOF will not really save you.

A night shot on a tripod should not be a stretch for any lens. It just depends how long an exposure you want to wait for. Remember, 4x5-film guys routinely take 20-30 second exposures (at f11 or something).

Razr
12-10-2006, 10:12 AM
Why couldn't I get this in focus?

It was a night shot. I used a tripod, with a self-timer delay of 10 seconds. There was no wind.

Granted, it was at 240 mm. Over a block away. And I wasn't able to manually focus it any better. Is this just an impossible shot (at least with the $200 Sigma?)

Any suggestions?
Here's the EXIF: (I must have left the -1.7 EV on from the last set of shots)
Nikon D50
2006/11/19 19:59:57.7
JPEG (8-bit) Fine
Image Size: Large (2000 x 3008)
Lens: 70-300mm F/4-5.6 D
Focal Length: 240mm
Exposure Mode: Aperture Priority
Metering Mode: Spot
Aperture priority? Use your tripod and full manual mode (only) for all your available light shots.
Is your "spot meter" a true spot (2.5 to 3.5 degrre) meter or an "area" spot?
Did you use your self-timer?
The -1.7 EV should not have affected the shot in any negative way

SpecialK
12-10-2006, 10:20 AM
The soft image is the probem, not metering method or exposure.

toriaj
12-11-2006, 08:20 PM
Aperture priority? Use your tripod and full manual mode (only) for all your available light shots.
Is your "spot meter" a true spot (2.5 to 3.5 degrre) meter or an "area" spot?
Did you use your self-timer?
The -1.7 EV should not have affected the shot in any negative way

Wow, thanks for all the help, everybody.

Razr, I've used Aperture Priority often. I only recently ventured into full manual ... I'll remember your advice. Maybe look at the settings the camera would choose in Aperture Priority, move to Manual, try those settings and go from there?

I don't really know about the spot meter ... it's the D50. I just put the selected focus bracket on the place I want to meter for, and push the button. Is that an area spot?

I did use the self-timer. Thanks again for all your help.

tcadwall
12-12-2006, 06:52 AM
I quickly scanned through the thread, so if someone already suggested this, sorry..

How are you releasing the shutter? That is the first thing that comes to my mind.

I would set the focus, and then use my ML-L3 remote for the shutter release. All the other suggestions are good, but I don't think that mirror-lockup should be necessary since I have seen very sharp night cityscapes come from D50's. Since the remote only costs a few bucks (read under $20) by my memory, it might not be a bad idea to get 2 of them in case you lose one (they are very small). This will work with your D50.

toriaj
12-12-2006, 11:33 PM
I was using the 10-second self-timer. Everyone's advice has been a big help. I haven't tried that shot again yet, but I did do some low-light shots at 300 mm (see http://www.dcresource.com/forums/showthread.php?p=181265&highlight=husband#post181265 ) and I was pleased with the focus. (Although I was just at the minimum focusing distance. A different environment. But I was able to use what I learned here.) Thanks again!

jnpalma
12-15-2006, 09:17 AM
Dear Toriaj,

May I use your picture and get some help from a digital software to work on it please ? ;)

By using digital software I notice that the better focus is on the top of the tower going down maybe to 1/3 of the buildling height.

I understand you want to get it done without any software help. I'm like that too.

I hope all tips here help you next time. It's a beautiful shot though.

Have fun !!! :)

toriaj
12-16-2006, 10:25 AM
Thanks, jnpalma. It looks much sharper now. What did you do?

jnpalma
12-18-2006, 05:35 PM
I used Photoshop (Unsharp Mask feature), had contrast, hue, levels and light adjusted....it takes around 2min to correct that if you have little experience.

You could also use Photoshop to bring the focus to another region by sharpening it more than the rest of the picture.

Anyway, as I said before I always try to get the best picture out of the camera the 1st time without using any software....however sometimes it helps a lot ;)