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Forum Elite
Posts: 14,342
Registered: ‎12-07-2012

Re: Lens Diffraction vs Image Quality

Ed,

This is not correct.

"the diffraction blurring does not depend on the lens focal length, but only on the f-number."

 

Diffraction is worse with WA and UWA lenses because of the short FL. Why?  Because the hole in the diaphram is smaller at any given f-stop compared to the same f-stop in a normal or tele typle lens. In a WA/UAW the light path is bent at a greater  angle.

 

Another factor is sensor size and pixel size. A camera like the 7D Mk II has fairly small pixels. Its going to be affected sooner than a camera with larger sensor and pixels.

 

It becomes a photographers decission as shooting at wide open apertures all lenses suffer form optical aberrations.  This is one reason most all lenses show their best when stopped down one or two stops. Diffraction is usually even where aberation is not. This makes diffraction less destructive to lens IQ.

 

How about DOF. DOF affects different parts of a scene with differing amounts. Remember we said diffraction is even, however, DOF is not.  The farther away from the focal plane you are, the more blurry your picture will get.

 

Diffraction is easy to correct in Photosop with smart sharpening and/or unsharp mask. Resolving power of most lenses is at its highest or best in the f4 to f8 range. Just anoher factor to consider. 

 

 

EB
EOS 1DX and 1D Mk IV and several lenses!
Frequent Contributor
Posts: 111
Registered: ‎01-04-2013

Re: Lens Diffraction vs Image Quality

EB,

 

How do you do a pano, composed of several shots, with movimg subjects?

 

Ed

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Posts: 11,950
Registered: ‎08-13-2015

Re: Lens Diffraction vs Image Quality


@Edward1064 wrote:

EB,

 

How do you do a pano, composed of several shots, with movimg subjects?

 

Ed


I have never purposely tried it.  But, you can probably pull it off using a high frame rate, provided your subjects are neither moving quickly or close to the camera.  

 

For example,I have captured pano shots of a bridge with moving vehicles,  The individual frames are fine, and are free of any motion blur from moving vehicles.  The only potential for real issues would occur at where the images overlap.  The stitching algorithms tend to throw away differences, and keep what is similar.  

 

Provded your subjects are not moving any significant difference across the frame from one shot to the next, you should be fine under those circumstances.E2414AC3-9D0A-432A-84A2-41571C69883D.jpeg

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"Doctor told me to get out and walk, so I bought a Canon."
VIP
Posts: 11,950
Registered: ‎08-13-2015

Re: Lens Diffraction vs Image Quality

[ Edited ]

@Edward1064 wrote:

Hi Waddizle,

 

Thank you for your responses.  I guess I should tell a little of the backstory.  

 

For several years I have been a bird photographer, using the 7DII and a Canon 100-400 mm II lens.  While hiking, we met another hiker who was doing panoramic photography, and I became interested. Something else to learn. So I set about photographing a unique Monterey Cypress tree at Point Lobos, near Carmel, Ca.  I wanted to make a panorama that included a little of its surroundings, on a cliff above the ocean. It was an experimental adventure, camera handheld in portrait orientation, using a couple of ideas I had gleaned from online reading.  Namely, shoot at high f-numbers for DOF (not really so relevant in this case since the subject was not so close) and in manual mode with fixed focal length.  It turns that a panorama does not enhance the Cypress tree.  See the Monterey Cypress below. It has a name: the Old Veteran.

 

I also took single shots of the Cypress at f/8 that looked a little better than the ones that were to be part of the panorama, taken at higher f-numbers, which got me thinking about diffraction. Thus the derivation that shows the diffraction depends on lens f-number in a straightforward way.

 

Yesterday I received an L-bracket for the 7DII and will use it on my tripod for the next reound of tests with various f-numbers.

 

Ed

 

 

 

Monterey Cypress


You should not need an L-bracket with the 100-400mm, or a 70-200mm.  With those lenses you should be using the tripod foot, not an L-bracket, anyway.  Rotate the camera to portrait mode within the lens collar.  

 

I shot the bridge using a 70-200mm, and rotating the rig within the tripod ring on the lens.  Capturing a panorama does not capture more detail, at least not exactly.  I could capture a similar angle of view shooting the bridge at 24mm.  But, I can create  a higher resolution final image by capturing a series of pano shots while zoomed in on the details.  I shot at 7

I shot the bridge with a 20MP 6D.  The final image was 38MB.  The pixel resolution of the final pano image was, of course, much higher than the 20MP image shot at 24mm.

 

It seems like you were some distance from this beautiful tree.  Capturing a pano image of the tree and its immediate surroundings with a long lens should have more detail than a single photo with a similar angle of view captured using a shorter lens.

 

But, the individual samples captured for a panoramic shot will not look any better than a single still of the same scene that was shot at the same focal length.  The longer lens allows you to zoom in on the details that elude a wider angle lens.

 

[EDIT] I forgot to add the reason I posted the bridge photo.  It was shot in Av mode, at ISO 100.  Each frame used an 8 second shutter speed.  My shooting position forced me to have a sidewalk between me and the bridge.  I could not set up camp in the middle of the sidewalk.

 

During the course of capturing the shots, a couple of joggers passed in front of the camera, as well as a couple that walked past the camera.  Seeing how I was piddling with my smart phone while the shutter was open, they never realized that I was capturing a shot.  I reshot the sequence.  But, the original shots showed no trace of anyone having crossed in front of the camera, which is no doubt due to the long shutter speed.

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"Doctor told me to get out and walk, so I bought a Canon."
Forum Elite
Posts: 14,342
Registered: ‎12-07-2012

Re: Lens Diffraction vs Image Quality

Ed,

"How do you do a pano, composed of several shots, with movimg subjects?"

 

You really can't.  Or at least, you need to be aware of some compromise. The bridge photo, which I have seen many timers on here is beautiful, for sure, but you notice there is no definition in the water in the foreground. That is probably due to the fact it was moving waves or ripples.

 

A person or animal in a single frame will still remain sharp unless it is next to a seam area. If there is too much motion in the various shots Lightroom will not merge them.

 

I don't necessarily agree with a multi-shot pano being better IQ. It is certainly a bigger file but the individual shots are no more  higher IQ than any one single shot. This would greatly depend on camera, lenses and conditions. Panos are different than multi-focus stacking which can increase IQ. Panos take multiple shots and puts them together using LR, or some other software, to allow a wider final photo.  Usually because it can exceed what can be contained within just a single frame.

 

What you may not know is panos also have issues with parallax. A way to correct for parallax error is to use a nodal slide. I don't bother because I am not interested in the highest IQ of these shots because of their final usage. Which is another factor in your decission making, how is the photo going to be used. In fact the two shots shown were hand held using my 1DX, 24-70mm f2.8L lens @ f9.5 (using P modeSmiley Happy), SS 1/350 and ISO 200.

EB
EOS 1DX and 1D Mk IV and several lenses!
Frequent Contributor
Posts: 111
Registered: ‎01-04-2013

Re: Lens Diffraction vs Image Quality

Thanks, EB. I do know about the need to rotate the camera around the lens’s entrance pupil to eliminate parallax. I’ve made some panos in the backyard to show the issue. Using Lightroom to stitch. Will get a nodal slide if I really get into this!
Forum Elite
Posts: 14,342
Registered: ‎12-07-2012

Re: Lens Diffraction vs Image Quality

I tried to edit my first reply but the forum is being contrary. Won't let me edit!  There is a mistake in the description of the second example. It is one shot, not three.  A straight shot from the 24mm lens. I posted it for comparison. Same lens used in different ways. You decide.

EB
EOS 1DX and 1D Mk IV and several lenses!
VIP
Posts: 11,950
Registered: ‎08-13-2015

Re: Lens Diffraction vs Image Quality


@Edward1064 wrote:
Thanks, EB. I do know about the need to rotate the camera around the lens’s entrance pupil to eliminate parallax. I’ve made some panos in the backyard to show the issue. Using Lightroom to stitch. Will get a nodal slide if I really get into this!

For most landscape shots, parallax should not be an issue.  It does not become an issue until there are elements in the foreground that you wish to capture, which are relatively close to the camera compared to more distant subjects in a typical landscape shot.

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"Doctor told me to get out and walk, so I bought a Canon."
Forum Elite
Posts: 14,342
Registered: ‎12-07-2012

Re: Lens Diffraction vs Image Quality

"For most landscape shots, parallax should not be an issue."

 

Nothing is or is not an issue depending on, "...how is the photo going to be used."  For the end purpose of my shown pano, I took no special treatment. It is/was hand held and simply merged in LR.

 

 

EB
EOS 1DX and 1D Mk IV and several lenses!
Frequent Contributor
Posts: 37
Registered: ‎06-22-2021

Re: Lens Diffraction vs Image Quality

I have found this usefull: https://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

 

GMIC Richardson/Lucy deconvolutiion will remove some diffraction.

 

Digital Lens optimization in DPP removes some diffraction.

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