Why do my photos look softer than Live View with a 500mm mirror lens on a Canon T7i?
Asked 12/21/2020
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I’m using an Opteka 500mm mirror lens on a Canon T7i, on a tripod with a remote shutter release, trying to photograph the Moon and the Jupiter-Saturn conjunction. I focus manually in Live View using the magnified view, and the image looks reasonably sharp there. But when I take the photo, the recorded image looks noticeably softer or blurred compared with what I saw in Live View. I also saw the same issue when adding a 2x teleconverter. Why would the image look in focus in Live View but come out blurry in the actual shot?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
1
Your focus isn't changing. It's blur caused by vibration, possibly of the mirror and/or shutter. If you're not using a wired or wireless remote, it's also due to pressing the shutter button.
Beyond that, where I was located there was quite a bit of upper atmosphere turbulence shortly after sunset. With the planets low in the west, they're in the area of the sky most affected by the temperature differential along the terminator.
EOS 7D Mark II + Kenko 2.0X Teleplus PRO 300 DGX + EF 70-200mm f/2.8 L IS II. ISO 800, f/5.6, 1/1000. Wired remote with mirror lockup.
This shot of the Moon¹ taken during the conjunction, shows a lot of atmospheric turbulence. Parts of the Moon are much sharper than other parts that are all the same distance from the shooting position.
Or your exposure time may be too long and you're seeing blur due to the motion of the planets during the exposure.
¹ Postprocessed using a CT of 2500K (even when finishing in monochrome, CT will affect relative contrast of the different areas of the Moon), Monochrome, red filter, and adjustments to contrast, highlights, and shadows. Moderate NR and sharpening.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
5y ago
0
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The focus probably isn’t shifting. What you’re seeing is more likely blur from vibration and/or atmospheric turbulence.
At 500mm (and especially with a 2x teleconverter), even tiny vibrations can soften the shot. On a DSLR, mirror and shutter movement can cause blur, so use a sturdy tripod, remote release, and mirror lockup if available. A fast enough shutter speed also matters.
Atmospheric turbulence can be a big factor too, especially for planets and objects low in the sky near sunset. In Live View you may catch brief moments that look sharp, but the recorded frame can still be softened by unstable air.
Also, very high ISO won’t cause focus shift, but it can reduce fine detail. Try keeping ISO around 100–200 and use roughly 1/200s or faster if conditions allow.
Finally, inexpensive mirror lenses are known for modest sharpness, so even with good technique you may not get especially crisp results from that lens, and the teleconverter will usually make things worse.
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AI5y ago
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