Why do my Nikon D750 photos look blurry or show a slight double image, even on a tripod?
Asked 4/16/2018
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2 answers
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I’m photographing trains, both moving and static, with a Nikon D750 and Sigma 24-105mm f/4. Even when using a tripod, some parts of my images look soft or almost like a slight double image, especially fine details like trees or wires. I understand the basics of shutter speed, aperture, ISO, depth of field, and continuous focus, but I still don’t get consistently sharp results.
What should I check first? Could this be caused by aperture choice, focus point selection, or something else in my setup?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
1
I think the problem is, the lens/camera combination you are using cannot meet your expiations. Top that with the fact that most lenses are compromised when tasked to work at or near their maximum aperture. If I am right, you can run a simple test. Compose a shot similar to what you have posted. Make sure the visa contains electric lines and their associated poles plus trees. Set the camera on a tripod and focus on a distant tree or power line. Now shoot a series covering each f-stop your camera/lens has. Shoot the first a f/4 and note the shutter speed. Now stop down to 5.6 by cutting the shutter speed in half. Now shoot f/8, again cutting the shutter speed in half. Now shoot f/11, again cutting the shutter speed in half. I will bet that the shots at f/8 and f/11 will be just fine.
What you will have discovered is, every lens has “sweet spot” when it comes to aperture. As a rule of thumb, this will be about 2 f-stops stopped down from the maximum. Clarifying cut shutter in half -- each time you stop down, less light enters the camera, you must compensate by allowing the shutter to remain open twice as long.
As to focus: Your shots are essentially “landscapes” meaning most of the content is quite distant. My advice, for now, set your camera’s focus to infinity and take your shot. To refine, read about “hyperfocal distance”. This is a distance focusing setting that keeps infinity (as far as the eye can see) in focus while maximizing the focus of foreground objects. If you learn about hyperfocal, it will make a big difference (improvement).
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
8y ago
0
Generated from our catalog & community — verify before relying on it.
Two likely causes were raised: focus placement and lens sharpness at wide apertures.
First, verify exactly where the camera focused. Use single-point AF rather than multi-point so you control the focus location precisely, and enable the D750 playback option that shows the focus point used. If the camera focused somewhere other than your intended subject, nearby or distant details can look soft.
Second, test the lens at different apertures. Many lenses are less sharp at or near maximum aperture, and stopping down often improves fine detail noticeably. On a tripod, photograph a detailed distant scene with wires, poles, or trees, and shoot the same composition at f/4, f/5.6, f/8, and f/11, adjusting shutter speed to keep exposure consistent. Compare the results closely.
If the images become clearly sharper at f/8 or f/11, the issue may simply be that the lens performs better stopped down. If they are still inconsistent, the focus-point check will help confirm whether autofocus placement is the real problem.
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