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#1
Posted 18 September 2021 - 03:11 PM
#2
Posted 19 September 2021 - 12:38 AM
IQ differs a lot between different mirror lenses. I have no experience with the one you're using here. I have used Tamron Adaptall lenses and they definitely perform a lot better than this. There is also a variance between copies and you can find good and bad with all brands.
The shot here could also suffer from motion blur. It's hard to tell from only one shot.
I don't think that you could clean away the problem here. Some dust doesn't affect the shots.
Bottom line, mirror lenses can be fun but don't expect them to outperform normal lenses. With a good quality 300 mm you should be able to get netter results cropping.
- TBonz likes this
#3
Posted 19 September 2021 - 06:53 AM
A sideeffect of the unexpensive solution with little correction by glass, especially in the narrow lens tube, is that imagequality suffers. As Bengan however mentioned there are different qualities on the market, each going with their own pricetag.
Another aspect to consider is the small max aperture (f8) which is at the absolute limit for getting enough light to autofocus.
In general don’t expect a mirrorlens to outperform an average glass based lens.
Mirror based lenses *might* be interesting for astronomy due to the long focal lenghts, but then again it will not be a single capture to take, but multiple ones which are then processed and combined (allowing to correct for some bluriness)
As for the example capture given here, have a look at the top of the writing « Kabel » or the top of the smaller pole/stick. You will identify a shadowzone, larger than the thickness of the writing. A clear indication that the lens moved vertically during the shot.
- TBonz likes this
#4
Posted 19 September 2021 - 08:37 AM
Everything that Bengt & Jerry_ wrote.
Also, I find mine difficult to focus in poor light.
My best moon shot with my Tamron mirror 500 + x2 teleconverter is only just about ok.
#5
Posted 19 September 2021 - 10:16 AM
Thank you all.
I looked at some other photos (including both more of the same island and some (poor) photos of the moon) this effect is actually visible in all of them. I did use the moon for testing when I cleaned the lens but I wanted to do a comparative test on something more realistic. On the moon photos the top side is smooth, suggesting that the camera is moving down. This sounds like there could be a tripod issue. I should investigate this and also try to take some photos in portrait mode.
Also, I don't expect a mirror lens to outperform a glass lens in general, however I thought that the 500/300 mm difference would show. Otherwise we could all do like the phone photographers, shoot everything in wide and crop...
#6
Posted 19 September 2021 - 01:15 PM
If I remember correctly, the best 500 cat in F-mount was the Tokina, closely followed by the Nikon with the Tamron SP and Vivitar series one trailing a bit behind. Then there were the cats from Panagor etc and the lowest quality from the Exakta. I think the Hansa is at about the same level as the Panagor.
The best overall were the Minoltas, Pentaxes and Olympus catadioptric lenses.
#7
Guest_ctintera605_*
Posted 12 September 2022 - 04:58 AM
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