Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-05-2010, 12:53 AM   #1
Junior Member
ladybug's Avatar

Join Date: Jun 2010
Posts: 38
Hyperfocus and diffraction help.

I was browsing youtube for some photo tutorials and came across this clip:

[YT]http://www.youtube.com/watch?v=uQ6DqhPuPpQ[/YT]

For a DSLR with cropped sensor, Bryan suggested a setting like this to achieve hyperfocusing.

lens 12mm - 16mm - F22 and 3 feet
lens 17mm - 18mm - F22 and 7 feet

And he quickly explained that he gets a lot of email about using F22 as that will not render a sharp image and he refuted that argument.

I have searched this forum and came across plenty of posts that suggest that at F22 diffraction certainly comes in and the picture is not at its sharpest.

What do u guys think?

Please, this is not a troll post. just trying to figure out something which i am not smart enough for.

09-05-2010, 05:30 AM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
It all depends on how big you blow up an image

Smaller apertures will lead to refraction and loss of quality but whether you can notice outside of a lab or not is a different question
09-05-2010, 11:32 AM   #3
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
There is no such thing as refuting the argument that f/22 is softer than f/8 - that's like refuting the law of gravity. There is no getting around physics. The only question is whether it is *enough* softer to matter. That is something only you can decide, and I would expect the answer to be different for each picture. All Bryan is saying he is htat he personally doesn't feel the loss in sharpness is big enough for him to worry about, but YMMV. We all have different tastes in food, spouses, and in virtually everything else subjective; no reason to assume his subjective impressions of how important that loss in sharpness is would match yours. Test it for yourself - again, don't assume that the tradeoff that makes sense for one image will make sense for all.
05-10-2012, 01:06 AM   #4
New Member




Join Date: Mar 2012
Location: Melbourne, Victoria
Posts: 24
Ladybug,
thanks for starting the thread

Others who have posted,
thanks for the info you have supplied.

If you have not seen it, you may be interested in the post on 9th May (I think) by wombat2go in the <Pentax Q Forum →Do teleconverters count toward diffraction equation?> and the illustrations he supplies of exposures at f/8 and f/32 of a pinhole backlit by an LED. At f/8 burrs silhouetted at the edge of the hole are clearly defined but quite blurred in the f/32 shot.





05-10-2012, 04:28 AM   #5
Pentaxian
JinDesu's Avatar

Join Date: Jun 2011
Location: New York City
Photos: Gallery
Posts: 5,626
It may also depend on the lens - I know that I was confused as to why my Sigma 10-20 F4-5.6 was taking very soft shots, and then I found out that it was because I didn't mount it properly and it was shooting stopped down at F22. I should have noticed because the shutter speeds were abnormally long.

After remounting it correctly and shooting at F8-F11, I was resolving a lot more detail. I can't provide examples, but I was in Grand Central Station shooting from one staircase across the large lobby - at F8, I could see the criss-cross of the window frames at 300' feet away. At F22, it was too blurred to define anything.
05-10-2012, 05:14 AM   #6
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
it all boils down to all the conditions of the image, not limited to but including how big the final image is projected. Remember things might look sharp on a 4x6 print (remember from the dark ages of film) but just blow that same image up to 13 x 19 (the size of the monitor I am in front of at the moment and it looks a lot worse.

acceptably sharp is a relative term usually based on the print film era of what looked good on an 8 x 10 print.
05-10-2012, 10:09 AM   #7
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,157
There will certainly be some loss of sharpness at very small apertures, but this is the tradeoff for securing very deep depth of field. If you need the DOF, then you have to accept the resolution loss.
05-12-2012, 01:03 AM   #8
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,406
Lens manufacturers should not even let you stop down past f11, the results will be terrible because of diffraction

K-7 with kit DA 18-55 WR and a cheap Sony macro lens adaptor stuck on the front. f40. Full size on Flickr.




05-12-2012, 01:16 AM   #9
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
On APS, diffraction at f/22 will be noticeable with 1) tripodded images that are 2) closely inspected (pixel-peeped). With handheld shots, even with SR on, diffraction will usually be swamped by lens-motion blur. All this is rather easy to test, to see for one's self.
05-12-2012, 11:09 AM   #10
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by kh1234567890 Quote
Lens manufacturers should not even let you stop down past f11, the results will be terrible because of diffraction
I'm not sure what your point is, but that image does suffer from very noticeable diffraction effects from the tiny aperture, as well as pretty obvious CA effects from the (presumably) single-element diopter. These are pretty apparent at the posted size, glaringly obvious at full size. I mean, it's usable for what it is, but compared to an image taken at f/11 and without the diopter, it's nowhere near as sharp as it could be.
05-12-2012, 02:37 PM   #11
Pentaxian
kh1234567890's Avatar

Join Date: Sep 2010
Location: Manchester, UK
Photos: Gallery
Posts: 2,406
QuoteOriginally posted by Marc Sabatella Quote
I'm not sure what your point is.
There is none. As usual, my posts on here are meant to be completely pointless.
05-12-2012, 02:44 PM   #12
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,002
QuoteOriginally posted by Marc Sabatella Quote
I'm not sure what your point is, but that image does suffer from very noticeable diffraction effects from the tiny aperture, as well as pretty obvious CA effects from the (presumably) single-element diopter. These are pretty apparent at the posted size, glaringly obvious at full size. I mean, it's usable for what it is, but compared to an image taken at f/11 and without the diopter, it's nowhere near as sharp as it could be.
Obvious CA? Where?
05-13-2012, 01:46 PM   #13
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by vonBaloney Quote
Obvious CA? Where?
The high contrast edges of the bird - the ends of the hairs - and highlights within. Not the sort of CA that manifests as purple fringing; more just an odd "glow" to the edges and highlights that is typical of the use of single element closeup lenses.
05-13-2012, 04:53 PM   #14
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
If you enlarge a perfect f:22 image by a factor of 10 (ie. APS-C sensor to a display about 240mm wide) the diffraction spot size will be about 0.3mm diameter for 550nm light; larger than a pixel on a typical electronic display.

This implies that 4x6 display would look pretty good.

Dave in Iowa

PS A good approximation for diffraction spot diameter (in micrometers) is 4*F-number/3.

Last edited by newarts; 05-13-2012 at 05:02 PM.
05-13-2012, 05:05 PM   #15
Ash
Community Manager
Loyal Site Supporter
Ash's Avatar

Join Date: Mar 2007
Location: Toowoomba, Queensland
Photos: Gallery | Albums
Posts: 22,695
Yes, diffraction creeps in with smaller apertures. Some lenses handle small apertures quite badly and yet some do well even at the smallest if apertures. I've done a couple of kit lens f/40 shots but was put off using it often more due to the loss of contrast and colour brilliance. As for sharpness, it was acceptably sharp to me, even at full-size on the K10D (don't know how it would fare with the K-5).
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, diffraction, f22, feet, lens, pentax help, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Diffraction in pentax 67 lenses Herb Pentax Medium Format 25 02-23-2010 12:37 PM
Diffraction Limits revisited RioRico Pentax DSLR Discussion 48 05-25-2009 09:56 AM
Diffraction Article by Lloyd Chambers philbaum General Talk 28 01-16-2009 12:48 AM
Silly question but how to set the DA14 to hyperfocus? raider Pentax SLR Lens Discussion 3 10-11-2008 09:14 PM
Diffraction issue montecarlo Photographic Technique 12 09-10-2008 11:12 PM



All times are GMT -7. The time now is 07:53 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top