Sharpest F Stop for D90 Video
- Thread starter mrmoe
- Start date
Sharpy rules of thumb
Sharpy rules of thumb
5 good rules of thumb for sharp lenses-
1. Primes are sharper than Zooms.
2. Nikkor is better than Discount.
3. The "sharpest" f/stop is 1-2 stops below wide-open.
4. Glass is sharper than Plastic.
5. Take that filter off!
In general, prime (or "fixed") lenses are sharper than zoom lenses. When zoom lenses first came out 30 or 40 years ago, this was especially so, but in recent years the performance difference has dropped dramatically. If you're willing to pay thousands of dollars, you can buy zoom lenses that are almost as sharp as primes.
Zoom lenses require more lens elements, and the engineers have to compromise quality, usually at the extremes of the lens range and at the image edges. So a cheap zoom lens will often have a defocused, vignetted effect when shot wide open at the widest setting (f/2.8 @ 17mm on a 17-55mm, f/2.8 lens).
Prime lenses do not require as many lens elements, as the elements do not need to move (hence "fixed"). And since there isn't as much engineering going into the lens, they don't cost as much.
Nikon has been designing lenses for a long time now, and they've easily got more patents than Tokina, Tamron or Sigma. So you might as well stick with the best.
The sweet spot of sharpness is 1-2 f/stops below wide open. So if you've got an f/2 lens, then f/2.8 to f/4 will produce the sharpest image. There are thousands of posts on the web as to why & how this happens- personally, I really don't care how it works, I just know that it does...
Finally, the best way to soften the image on any lens is to slap a crappy "sky" filter on the front. You wouldn't wear dollar store sunglasses, so why would you put a $15 filter on the front of your $500 lens? I'll grant that there are situations in which filters are necessary, but digital white balancing has eliminating many of those situations...
Sharpy rules of thumb
5 good rules of thumb for sharp lenses-
1. Primes are sharper than Zooms.
2. Nikkor is better than Discount.
3. The "sharpest" f/stop is 1-2 stops below wide-open.
4. Glass is sharper than Plastic.
5. Take that filter off!
In general, prime (or "fixed") lenses are sharper than zoom lenses. When zoom lenses first came out 30 or 40 years ago, this was especially so, but in recent years the performance difference has dropped dramatically. If you're willing to pay thousands of dollars, you can buy zoom lenses that are almost as sharp as primes.
Zoom lenses require more lens elements, and the engineers have to compromise quality, usually at the extremes of the lens range and at the image edges. So a cheap zoom lens will often have a defocused, vignetted effect when shot wide open at the widest setting (f/2.8 @ 17mm on a 17-55mm, f/2.8 lens).
Prime lenses do not require as many lens elements, as the elements do not need to move (hence "fixed"). And since there isn't as much engineering going into the lens, they don't cost as much.
Nikon has been designing lenses for a long time now, and they've easily got more patents than Tokina, Tamron or Sigma. So you might as well stick with the best.
The sweet spot of sharpness is 1-2 f/stops below wide open. So if you've got an f/2 lens, then f/2.8 to f/4 will produce the sharpest image. There are thousands of posts on the web as to why & how this happens- personally, I really don't care how it works, I just know that it does...
Finally, the best way to soften the image on any lens is to slap a crappy "sky" filter on the front. You wouldn't wear dollar store sunglasses, so why would you put a $15 filter on the front of your $500 lens? I'll grant that there are situations in which filters are necessary, but digital white balancing has eliminating many of those situations...
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I really doubt that. I REALLY do. Got anything that can convince me?
You know, even my Iphone is sharp at 1280x720.
my camera salesman told me it's f5.6 and up if you want sharpness and the sensor inside the dslr to do it's magical thing. Sadly, he's right.. the sensor needs a little bit more light to properly do it's job (especially auto focus). i have less problems with my still cameras now knowing that little fact.
pveal
Well-known member
...and wide open.
thanks, I began my day cackling out loud.
Urkas, I see you point about low bitrate etc but If you doubt or don't believe that good quality glass improves your image, if the informed opinion of others still leaves you suspicious then the only way to know for sure (aside from a side by side screen grab comparison of nikkor prime versus the rest) is to try it out for yourself. I have certainly noticed a difference between 28 2.8 AI, 50 1.4 AI and 18-200 3.5 VR.
If you really want to find the sharpest f stop for a lens take a series of pictures in RAW, on a tripod, at different f stops and compare them at the edges of the picture and the center. Use a scene that will remain constant, and as well defined objects. (So not landscape) And just check the sharpness in post by zooming in 100 percent.
And the poster above is correct about that primes usually give you more sharpness, although if you have the money you can get a 4K dollar lens that might be sharper than a prime.
And the poster above is correct about that primes usually give you more sharpness, although if you have the money you can get a 4K dollar lens that might be sharper than a prime.
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Ye sure, there is a diffrent in sharpness at diffrent f-stops. When your taking 12mpix images that is.
But if your lens isn't sharp at 720p your lens aint good enough for anything. As I said, even my iphone is sharp at that resolution.
And remember, the topic was about sharpness, nothing else.
Mattias: If thats your best argument then you've already failed.
But if your lens isn't sharp at 720p your lens aint good enough for anything. As I said, even my iphone is sharp at that resolution.
And remember, the topic was about sharpness, nothing else.
Mattias: If thats your best argument then you've already failed.
You don't want to go too high in F-stops if sharpness is your main priority, or you start to lose sharpness again, like around 16 and above in many cases. (This is in reference to stills)
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So by that rationale there is no difference in sharpness to be noticed between f1.8 and f4 (the sweet spot (ish)) on nikon 50mm prime shot with a d90? I got curious about this and decided to do a test as im new to all this video with prime lenses on DSLRs business (who isn't!). Just want to see for myself how much the rules of high res stills applys to a much lower resolution. All my common sense says it absolutely does translate. Even evident at much lower resolutions than 720p.
I find this forum great by the way.
Just scrub forward and back on this video to have a look for yourselves.
http://www.vimeo.com/3520639
By the way, before focus is blamed the box is sharp. But if not pick another point in the woodgrain.
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the point of the exercise was to show how bad *your* best argument was. i'm not in this to win, if you don't want to learn it's your loss completely.
/matt
taubkin
Veteran
Absolutely, it makes a huge difference. Especially since we're working with 30+ year old lenses for manual control. Today's lenses are much better in this regard, and even "crappy" lenses like tokina and sigma zooms, are pretty good in that respect. Of course todays lenses tend to be much slower (thus sharper) because of digital's higher sensitivity.