Home · Register · Search · View Winners · Software · Hosting · Software · Join Upload & Sell

Moderated by: Fred Miranda
Username   Password

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Canon Forum | Join Upload & Sell

1
       2       3       end
  

Archive 2012 · diffraction as you stop down
  
 
dave chilvers
Offline
• • •
Upload & Sell: Off
p.1 #1 · p.1 #1 · diffraction as you stop down


I`ve just been having a read on this web page http://www.kenrockwell.com/tech/diffraction.htm

OK! I`m not a big fan of Ken so what would you lads think is the point that diffraction takes away IQ when using something like the 17-40, would it be around f8?

Thanks



Apr 05, 2012 at 07:22 PM
Geofn
Offline
• • •
Upload & Sell: Off
p.1 #2 · p.1 #2 · diffraction as you stop down


Pixel peeping at 100% aside, on full frame I think you would be hard pressed to see any degradation from diffraction before f11.


Apr 05, 2012 at 07:44 PM
Monito
Offline
• • • • • •
Upload & Sell: Off
p.1 #3 · p.1 #3 · diffraction as you stop down


Diffraction degradation depends on the sensor and aperture, not on the lens.

See this tutorial: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm



Apr 05, 2012 at 07:51 PM
John Shultz
Offline
• •
Upload & Sell: Off
p.1 #4 · p.1 #4 · diffraction as you stop down


Sensor size, the pixel pitch of said sensor, total depth of field in the scene being imaged, and final print size all play a roll. Cambridge in color = good explanation.

Ken Rockwell reminds me once again with his article here how poor he is at conveying anything of substance. "Squint your eyes, that is diffraction!"



Apr 05, 2012 at 08:32 PM
artd
Offline
• • •
Upload & Sell: Off
p.1 #5 · p.1 #5 · diffraction as you stop down


On a DSLR I would not worry about diffraction at f/8, at least certainly not on a full frame DSLR. I doubt you'd see much impact even at f/11. And keep in mind that diffraction onset is gradual. You may see a big difference between f/11 and f/22, but probably not as big a difference between f/11 and f/13, for instance.

Diffraction vs depth of field is always a trade off but it depends on the particular photo. If you have subject matter both near and far that you need to be in focus, it may be better to have a wider area a little softer but all in focus than it is to have one narrow area sharp and in focus but the rest out of focus.

Don't forget too that at as pixels get downsampled (you print smaller) then the effects of diffraction also get minimized.



Apr 05, 2012 at 09:02 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.1 #6 · p.1 #6 · diffraction as you stop down


There is a lot of confusion on this subject mainly because of online "diffraction limit" calculators. (Including the site mentioned above)
There is not really a "limit" where a f/stop causes resolution to suddenly fall. In practice, crossing some threshold will not all of the sudden limit resolution. It's more like a gradual graph slope as aperture narrows. The proof is in the MTF (resolution) curve graphs.

Basically, even a perfect lens aberration will impact resolution at larger apertures and diffraction as it's stopped down. Most great lenses have a sweet spot between f/4 and f/8. Around f/4 aberration is no longer the prominent cause of resolution loss and around f/8, diffraction becomes the main cause. It's safe to say that most lenses need to be stopped down 1 or 2 stops for maximum resolution.

The sensor pixel density will not affect diffraction and that is the problem with these calculators. For example, a 36MP sensor will capture whatever diffraction is already coming through the lens. It's not creating more diffraction, it's just recording diffraction more efficiently which in turn, will become more evident in our pictures.

In the case of the 17-40mm, resolution level is dependent on the focal length used. The best "center" resolution would be around f/5.6-f/8 and after that diffraction becomes the main source of resolution loss. I agree with you. f/8 seems to be a good compromise.



Apr 05, 2012 at 09:49 PM
Monito
Offline
• • • • • •
Upload & Sell: Off
p.1 #7 · p.1 #7 · diffraction as you stop down


Fred Miranda wrote:
There is not really a "limit" where a f/stop causes resolution to suddenly fall. In practice, crossing some threshold will not all of the sudden limit resolution. It's more like a gradual graph slope as aperture narrows. The proof is in the MTF (resolution) curve graphs.


+1 Same thing for depth of field and many other continuosly variable phenomena that people love to try to turn into yes/no go/nogo binary phenomena.




Apr 05, 2012 at 09:53 PM
georgesaad
Offline

Upload & Sell: Off
p.1 #8 · p.1 #8 · diffraction as you stop down


Could someone please post an actual sample of "diffraction" in a landscape photo scene? thank you


Apr 05, 2012 at 09:53 PM
AJSJones
Offline
• • •
Upload & Sell: Off
p.1 #9 · p.1 #9 · diffraction as you stop down


georgesaad wrote:
Could someone please post an actual sample of "diffraction" in a landscape photo scene? thank you

A better way to see the effect would be to see for yourself how stopping down affects the sharpness of a subject of your own choice - a nearby tree with lots of leaf detail would be a landscaper's choice (it's their "test target" !). Just find a nice subject and take a series of shots as you stop down, then look at them a 100% view on screen. The increasing blur is the effect of diffraction.



Apr 05, 2012 at 10:01 PM
georgesaad
Offline

Upload & Sell: Off
p.1 #10 · p.1 #10 · diffraction as you stop down


AJSJones wrote:
A better way to see the effect would be to see for yourself how stopping down affects the sharpness of a subject of your own choice - a nearby tree with lots of leaf detail would be a landscaper's choice (it's their "test target" !). Just find a nice subject and take a series of shots as you stop down, then look at them a 100% view on screen. The increasing blur is the effect of diffraction.


Yes thank you, I have been experiencing this issue for a while now, and since all I shoot is landscape, it is a problem that I face quiet often..is there any work around it aside form sharpening in post?
-I use a tripod and a shutter release to avoid camera shake- MKII/17-40.



Apr 05, 2012 at 10:11 PM
 

Search in Used Dept. 



bobsofpa
Offline
• • •
Upload & Sell: Off
p.1 #11 · p.1 #11 · diffraction as you stop down


The new DPP is "supposed" to correct for diffraction (DLO). Once they get a version out without bugs we will be able to see how good a job it does. The list of lenses that have been programed for this feature is rather limited at this time but hopefully more will be added in the future.


Apr 05, 2012 at 10:23 PM
jcolwell
Offline
• • • • • • •
Upload & Sell: On
p.1 #12 · p.1 #12 · diffraction as you stop down


georgesaad wrote:
Could someone please post an actual sample of "diffraction" in a landscape photo scene? thank you


I recently posted some images from my new X-Pro 1 on the Alt forum. The first three sets of four images shows the XF 18/2R lens is relatively sharp at f/8, but diffraction effects become increasingly apparent at f/11 and f/16.

http://www.fredmiranda.com/forum/topic/1100128/0#10495813



Apr 05, 2012 at 10:42 PM
RustyBug
Online
• • • • • •
Upload & Sell: On
p.1 #13 · p.1 #13 · diffraction as you stop down


Monito wrote:
Diffraction degradation depends on the sensor and aperture, not on the lens.

See this tutorial: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm


+1

Shooting @ 14MP on SLR/c, I can see a difference in contrast between f8 & f16 ... so I try to limit my aperture selection to f11 on most occassions ... but I won't let it stop me from using f16 if I need to slow down my shutter.

Regarding the CIC tutorial / interactive pixel matrix ... I tend to think that a 1/3 pixel overlap is still a very safe amount ... more than 1/2 - 2/3 overlap and I think you'll see it being more evident.


Edited on Apr 06, 2012 at 01:51 AM · View previous versions



Apr 05, 2012 at 10:42 PM
georgesaad
Offline

Upload & Sell: Off
p.1 #14 · p.1 #14 · diffraction as you stop down


I shot this earlier today. 17-40








Apr 05, 2012 at 10:47 PM
Photon
Offline
• • • • • •
Upload & Sell: On
p.1 #15 · p.1 #15 · diffraction as you stop down


georgesaad wrote:
Yes thank you, I have been experiencing this issue for a while now, and since all I shoot is landscape, it is a problem that I face quiet often..is there any work around it aside form sharpening in post?
-I use a tripod and a shutter release to avoid camera shake- MKII/17-40.

Reading between the lines, it sounds as if you find you need to stop down a _lot_ to get the depth of field you need (f/16? 22?), and therefore the resolution is noticeably limited by diffraction. One solution is to use a TS-E lens, using tilt to get the plane of focus close to alignment with the ground in your field of view. That way you can often use an aperture like f/5.6 and still have everything in focus. Fred Miranda has posted (as have a few other photogs) some beautiful examples of this in various threads about TS lenses.



Apr 05, 2012 at 10:54 PM
veroman
Offline
• • • •
Upload & Sell: On
p.1 #16 · p.1 #16 · diffraction as you stop down


dave chilvers wrote:
I`ve just been having a read on this web page http://www.kenrockwell.com/tech/diffraction.htm
OK! I`m not a big fan of Ken so what would you lads think is the point that diffraction takes away IQ when using something like the 17-40, would it be around f8? Thanks


Ken Rockwell has a lot of things to say about a lot of things, and sometimes he's right on the money or at least in synch with what the rest of the photo community thinks/knows. Other times ... even most times ... well, that's another story.

Regarding diffraction: I consistently shoot at f/13 and f/16 with my Canon 5D Mark 1 with little to no ill effects ... at least none that are clearly discernible by either myself or my clients. Interior and architectural work demands these kinds of apertures for maximum DOF and background sharpness. I've also shot at f/22, but with that small an aperture, some degradation is noticeable; but NOT unusable! As Fred and others have pointed out, IQ doesn't suddenly fall off a cliff when you stop down to f/11 and beyond. It's not like going from ISO 200 to ISO 1600, where the differences are pretty clear. Diffraction is gradual and its effects are very dependent on any number of factors.
- Steve



Apr 05, 2012 at 10:55 PM
Photon
Offline
• • • • • •
Upload & Sell: On
p.1 #17 · p.1 #17 · diffraction as you stop down


OK, your example wasn't up when I was writing the above. I see you _were_ at f/16, which may account for the softness, though I'd still expect a bit more detail.


Apr 05, 2012 at 10:59 PM
RazorTM
Offline
• • •
Upload & Sell: On
p.1 #18 · p.1 #18 · diffraction as you stop down


Monito wrote:
Diffraction degradation depends on the sensor and aperture, not on the lens.

See this tutorial: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm


Did you read the whole article?

Here:
Even when a camera system is near or just past its diffraction limit, other factors such as focus accuracy, motion blur and imperfect lenses are likely to be more significant. Softening due to diffraction only becomes a limiting factor for total sharpness when using a sturdy tripod, mirror lock-up and a very high quality lens.

My opinion is that diffraction on the pixel level is something that you shouldn't even think about. Imagine a sensor with infinite resolution. It should theoretically be completely unusable at any normal aperture. Think of a sensor with 1, or 4, or 16 total pixels. How would diffraction affect it?

Basically, you should know your lenses well and where diffraction overpowers their ability to resolve the scene rather than being concerned with how many pixels are in your sensor.



Apr 05, 2012 at 11:07 PM
Monito
Offline
• • • • • •
Upload & Sell: Off
p.1 #19 · p.1 #19 · diffraction as you stop down


RazorTM wrote:
Did you read the whole article?

Here:



Yes, I did read the whole article. That doesn't contradict what I wrote. DId you read what I wrote?

The lens does not make any difference to the diffraction performance. The other characteristics of the lenses will indeed affect sharpness in the way quoted, but the contribution made by diffraction will be the same at the same aperture on the same sensor.



Apr 05, 2012 at 11:28 PM
dave chilvers
Offline
• • •
Upload & Sell: Off
p.1 #20 · p.1 #20 · diffraction as you stop down


Thanks guys, some good replies( thanks Fred)

I should have mentioned I shoot with a 5d2. I was shooting on a beach last week (distances were some at around 30-40 ft and some at infinity) with the 17-40 at f10 and ingeneral the images were pretty sharp. I was passing a small lake today where there had been some tree felling so I stopped to capture the mess before it was cleared away, again at f10 Iso 200 and around 20mm and distances of around 15-20ft (much closer than before) and although I can probably retrieve the images in post there was a definite lack of biting sharpness (in good light)

I quite often just use my contax 21mm (old style) at f8 and just leave it hard against infinity and to be quite honest I can`t remember (other than a genuine mistake) where the images were not on the button over a pretty big variation of distances, even f11 seems to look OK. Thats what caught me out a bit today really.I`m probably wrong but it would seem to me that everything tells me that the lens isn`t the deciding factor as has been stated earlier but the Contax shots just never seem to be unsharp.



Apr 05, 2012 at 11:49 PM
1
       2       3       end




FM Forums | Canon Forum | Join Upload & Sell

1
       2       3       end
    
 

You are not logged in. Login or Register

Username   Password    Reset password