Laowa 2:1 macro lens (Focus/Diffraction?) test
Sep 3, 2015 14:45:41 #
First let me state that I have never done this kind of lens test. I have way too many hours invested in this test so I hope it was done correctly. Here's the steps I followed:
1. Figured step sizes for aperture sizes.
2. Ran stacks at all apertures (f/2.8 - f/22) keeping ISO @ 200 & shutter @ 1/200 while increasing the power settings on flash units by 1 full stop for each decrease in f-stop (f/2.8=1/128 power, f/4=1/64 power, etc.). The exposures were pretty close until I went from f/8 to f/11, where a full stop increase of speedlight power overexposed the image. Power setting for f/8 & f/11 are the same. After that, the full-stop increase in power was reasonably close again.
3. Stacked all images & combined for easy comparison. I then repeated for a 4:1 test.
Reason for test: I can't get a sharp image at f/11 or f/8.
Do I have a bad lens?
Any and all comments will be appreciated, Thanks in advance.
1. Figured step sizes for aperture sizes.
2. Ran stacks at all apertures (f/2.8 - f/22) keeping ISO @ 200 & shutter @ 1/200 while increasing the power settings on flash units by 1 full stop for each decrease in f-stop (f/2.8=1/128 power, f/4=1/64 power, etc.). The exposures were pretty close until I went from f/8 to f/11, where a full stop increase of speedlight power overexposed the image. Power setting for f/8 & f/11 are the same. After that, the full-stop increase in power was reasonably close again.
3. Stacked all images & combined for easy comparison. I then repeated for a 4:1 test.
Reason for test: I can't get a sharp image at f/11 or f/8.
Do I have a bad lens?
Any and all comments will be appreciated, Thanks in advance.
Sep 3, 2015 15:10:51 #
If you did not do focus test and micro adjustment. Read this article and try. http://nikoneurope-en.custhelp.com/app/answers/detail/a_id/51633/~/how-to-use-the-af-fine-tune-function
Sep 3, 2015 15:17:29 #
At 2:1, I like your f/5.6 image best.
At 4:1, I like your f/5.6 image best.
I have no recommendations as how to compare your lens to other Laowa 60-mm 2:1 macro lenses.
At 4:1, I like your f/5.6 image best.
I have no recommendations as how to compare your lens to other Laowa 60-mm 2:1 macro lenses.
Sep 3, 2015 15:58:02 #
naturepics43 wrote:
looks as though camera/lens system diffraction limiting is biting your butt at anything more than F 5.6....Reason for test: I can't get a sharp image at f/11 or f/8....Do I have a bad lens? ...
Is that a crop frame camera?
Sep 3, 2015 16:00:16 #
Yes, f/5.6 seems to be your sweet spot. Thinking out loud, is your background to close too the point of the light from the flash bouncing back into the lens causing a contrasty look? Happens with tubes very easily. In the side by side I also noticed f/8 and beyond are still darker than the larger apertures. If your shooting raw, then you also have to sharpen your images, maybe this is a cause. I shoot only JPEGs and sharpen in camera. I also denoise each photo prior to running thru the stacking software. I hope you find out what's causing the problem.
Sep 3, 2015 16:02:30 #
oldtigger wrote:
At 2:1 I wouldn't think it would kill the shots this much, any higher I would agree. Look on the other side of F/5.6, photos are just as bad. Are you stacking at recommended distances per each f/stop. Adjusting your steps per over lap?looks as though camera/lens system diffraction limiting is biting your butt at anything more than f/5.6. Is that a crop frame camera?
Sep 3, 2015 18:42:00 #
Nikonian72 wrote:
Thanks for looking & commenting.At 2:1, I like your f/5.6 image best.
At 4:1, I like your f/5.6 image best.
I have no recommendations as how to compare your lens to other Laowa 60-mm 2:1 macro lenses.
At 4:1, I like your f/5.6 image best.
I have no recommendations as how to compare your lens to other Laowa 60-mm 2:1 macro lenses.
I agree that f 5.6 @ 2x is best but I'm not satisfied with any of the 4x settings.
Sep 3, 2015 18:45:23 #
oldtigger wrote:
Thanks for looking & commenting. Yes, Nikon D7000looks as though camera/lens system diffraction limiting is biteing your butt at anything more than f/5.6.
Is that a crop frame camera?
Is that a crop frame camera?
Sep 3, 2015 20:57:01 #
I have nothing to compare this lens with in terms of where the "sweet spot" is-- but I think you've found it for this lens. Amazing how bad the diffraction is as you stop down to f/22.
I think your test was well done.
I think your test was well done.
Sep 3, 2015 23:40:46 #
Pretty good test, very methodical.
From the look of the 4:1 images, it looks like vibration is causing you more problems at 4:1 than diffraction, even though you're using flash. Were you using Live View or normal mirror cycling?
You really can't expect good sharpness at 2:1 beyond f/5.6, or at 4:1 beyond f/4, on the D7000. The f/5.6 sweet spot at 4:1 may be due to the lens being way out of its design space due to the extensions. You might get a better result using a 2x teleconverter. Impact on effective aperture is the same as the extension, but the lens is still operating in its design window at 2:1, so overall might give a better result.
I've been thinking about doing just that for a while but life has been throwing me too many curve balls lately.
From the look of the 4:1 images, it looks like vibration is causing you more problems at 4:1 than diffraction, even though you're using flash. Were you using Live View or normal mirror cycling?
You really can't expect good sharpness at 2:1 beyond f/5.6, or at 4:1 beyond f/4, on the D7000. The f/5.6 sweet spot at 4:1 may be due to the lens being way out of its design space due to the extensions. You might get a better result using a 2x teleconverter. Impact on effective aperture is the same as the extension, but the lens is still operating in its design window at 2:1, so overall might give a better result.
I've been thinking about doing just that for a while but life has been throwing me too many curve balls lately.
Sep 4, 2015 11:40:52 #
martinfisherphoto wrote:
All good points. I'll try different lighting set up. I also stack using JPEG frames most of the time. I shoot raw + JPEG all the time since I read somewhere that sometimes with certain subjects you can get better detail with TIF files. I have been using the free CombineZP software since I started stacking several years ago. I just downloaded the trial Zerene software 2 weeks ago. WOW! Yes, f/5.6 seems to be your sweet spot. I shoot only JPEGs and sharpen in camera. I also denoise each photo prior to running thru the stacking software. I hope you find out what's causing the problem.
martinfisherphoto wrote:
I'm using the Zerene DoF (step size) charts but running my stacks at 1/2 the indicated step sizes so I think I have plenty of overlap. Thanks for all you're suggestions.Are you stacking at recommended distances per each f/stop. Adjusting your steps per over lap?
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