Aperture settings, DOF and Diffraction - samples

I'm aware of the problems diffraction can cause, when attempting to maximise depth of field and choosing a small aperture to achieve that goal. However, having spent some time in other threads, where people are following the advice in Bryan Peterson's "Understanding Exposure" religiously, as if it was their bible, I am concerned that some people may be suffering from soft pictures because they think f/22 is the holy grail for sharpness within a scene. Maybe it is with a full frame 35mm sensor, but I think for a crop body with a high megapixel count that opinion needs to be reviewed.

With that in mind, I've shot three sequences of photographs, at different aperture settings, to try to illustrate the problem, and uploaded them to a web album. I find the best way to study the impact of diffraction is to watch the images as a slideshow, or manually skip from each one to the next, so that each image appears in exactly the same place as its predecessor. I find it much harder to compare critical sharpness when viewing photos side by side. Flicking back and forth with a different image in the exact same place tends to emphasise the differences.

Anyway, here's the album - http://picasaweb.googl​e.co.uk …FStop?authkey=z​i1h_3k1k0s

The setup was my 40D mounted on a solid tripod, weighted with my camera bag hanging below. The lens was my 100-400 set to 100mm. I focused manually using Live View and 10X magnification. Once everything was locked down I shot in Live View mode, using a 2 second shutter delay to minimise vibration. The pictures are 100% centre crops. The images were shot in raw and cropped and output to jpeg using DPP. Sharpening was set to 3/10.

For each sequence the f/stops were - f/4.5, f/5.6, f/8, f/11, f/16, f/22, f/32. EXIF is intact.

I don't think the aerial shots show diffraction effects terribly well (although they are there), but they do show how sharp the lens can be. However, in the shots of the plant and the satellite LNB, what I find interesting is that at f/22 and f/32, rather than increasing DOF bringing the background into sharper focus, it actually seems to soften, with f/11 and f/16 clearly giving better results.

Something I've just noticed, as I was about to upload a couple of examples here as a teaser, is that the file sizes of each jpeg do vary between the different f/stop settings. The less detail present, the smaller the file. For the satellite dish shots, where the scene does not move at all, the f/stops and file sizes are....

4.5 = 148KB
5.6 = 153 KB
8.0 = 154 KB
11 = 152 KB
16 = 146 KB
22 = 135 KB
32 = 126 KB

So that puts some sort of objective measurement (I think) on the relative sharpness of each image and confirms that f/8 is the optimum while f/22 and f/32 are quite hopeless, relatively speaking.

I hope people find this little study useful. Any comments gratefully received

Here are shots at f/4.5 (the sharp image) and f/32 (the soft image). Focus was set manually on the back edge of the LNB (left hand side in the picture) to get the sharpest edge I could relative to the dish behind it.

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Excellent example. My immediate reaction is that we need to suggest Peterson to update his book based on similar examples. Now I understand MUCH better how to approach this subject.

THANKS!

Ferrari_Alex wrote in post #4940184
Excellent example. My immediate reaction is that we need to suggest Peterson to update his book based on similar examples. Now I understand MUCH better how to approach this subject.

THANKS!

Actually I'm feeling quite inclined to write my own "book". Whether I attempt to sell it or just give it away online is another matter. All the information is in the public domain and really it isn't rocket science - it just needs pulling together into a concise and comprehensible reference. I feel like I've half written it already, just responding to threads on POTN and elsewhere, as, of course, have many others. A sticky at the top of one of the forums should be more than adequate. People have kindly put in the effort to do similar things here for wedding photography, or flash photography, for example.

Either way, I don't believe the topic needs stretching to well over 100 pages. I should think about ten pages of text and another ten pages of pictures/examples should about cover it, at least for beginners. (OK, let's say 20+20, just in case ) How many pages are really required to say "meter off the sky" or "meter of the grass" or "meter off the palm of your hand", or a grey card, or a sheet of white A4 and bump up the EC by x.y stops? How many pages are required to say "Fire a test shot and check your histogram, then adjust exposure to suit."? How many pages are required to say - "A wide aperture gives a shallow DOF, a smaller aperture a deeper DOF."? How many pages are required to say "A high shutter speed freezes motion, while a slow shutter speed emphasises motion."? How many pages are required to explain spot vs partial vs CWA vs evaluative metering and when to use each variety? etc. etc..

I can be the one to test how good the book is, if you want It has to be simple and self explanatory, but also give a chance to get some deeper knowledge. The ideal situation is when you show people different example. Say the shot would look like this if you will do this and this.

One important things! Somehow all books are missing one point - what does it take to make shots that will eventually appear on the National Geographic cover. It can kill all desire to learn and understand photography, whereas results are about to come...just need to be patient, devote your time and be willing to learn and see the world in your own eyes

tdodd wrote in post #4940301
Actually I'm feeling quite inclined to write my own "book". Whether I attempt to sell it or just give it away online is another matter. All the information is in the public domain and really it isn't rocket science - it just needs pulling together into a concise and comprehensible reference. I feel like I've half written it already, just responding to threads on POTN and elsewhere, as, of course, have many others. A sticky at the top of one of the forums should be more than adequate. People have kindly put in the effort to do similar things here for wedding photography, or flash photography, for example.

Either way, I don't believe the topic needs stretching to well over 100 pages. I should think about ten pages of text and another ten pages of pictures/examples should about cover it, at least for beginners. (OK, let's say 20+20, just in case ) How many pages are really required to say "meter off the sky" or "meter of the grass" or "meter off the palm of your hand", or a grey card, or a sheet of white A4 and bump up the EC by x.y stops?

Ferrari_Alex wrote in post #4940371
One important things! Somehow all books are missing one point - what does it take to make shots that will eventually appear on the National Geographic cover. It can kill all desire to learn and understand photography, whereas results are about to come...just need to be patient, devote your time and be willing to learn and see the world in your own eyes

IMHO the first thing is to have an interesting subject. Without that you can shoot the most technically perfect image - but who will want to see it? - only a measurebator. I doubt many people will walk past a news stand and comment - "Wow, look at how the photographer nailed the eposure on that shot!" The subject is what will draw people in, the technical judgement comes afterwards. Of course, that has to be (near) perfect too.

Here's an analogy - would you rather watch a boring TV series or film in glorious high definition with full surround sound, or one of your favourite shows/films in standard def and plain old stereo? Personally I would not want to watch technically excellent "rubbish".

By the way, Bryan does have another book, called "Learning To See Creatively". I haven't read it so I can't comment on its usefulness, but it may help plug a gap in your understanding for capturing that magical image.

I perfectly understand what you mean, this is very correct and true. So why not to write a book and teach people how to see things in a creative way and also develop a "begin with the end in mind" photography thinking?

You have to be technically skilled enough to stand ready once the opportunity arises, therefore we need a book on:
1. Technical Mastery
2. Seeing things creative

tdodd wrote in post #4940438
IMHO the first thing is to have an interesting subject. Without that you can shoot the most technically perfect image - but who will want to see it? - only a measurebator. I doubt many people will walk past a news stand and comment - "Wow, look at how the photographer nailed the eposure on that shot!" The subject is what will draw people in, the technical judgement comes afterwards. Of course, that has to be (near) perfect too.

Here's an analogy - would you rather watch a boring TV series or film in glorious high definition with full surround sound, or one of your favourite shows/films in standard def and plain old stereo? Personally I would not want to watch technically excellent "rubbish".

tdodd & Alex.

This is great information!

I am very happy that you have shared this valuable & interesting detail!

You are a great teacher and have the ability to explain things clearly...

Thank you very much...

Roland

I guess tdodd is going to be famous

booju wrote in post #4942068
tdodd & Alex.

This is great information!

I am very happy that you have shared this valuable & interesting detail!

You are a great teacher and have the ability to explain things clearly...

Thank you very much...

Roland

tdodd wrote in post #4940301
Either way, I don't believe the topic needs stretching to well over 100 pages. I should think about ten pages of text and another ten pages of pictures/examples should a

If anybody can stretch this topic to well over 100 pages, it's the folk here on POTN!

Just ask lightrules.

Ferrari_Alex wrote in post #4940473
I perfectly understand what you mean, this is very correct and true. So why not to write a book and teach people how to see things in a creative way and also develop a "begin with the end in mind" photography thinking?

You have to be technically skilled enough to stand ready once the opportunity arises, therefore we need a book on:
1. Technical Mastery
2. Seeing things creative

Yes, yes, yes!!!

You have a GREAT style and skill in your presentation of the PRINCIPLES of PHOTOGRAPHY...

As beginners we can read and read but your explanations with live examples is very helpful and readily acquired!

Analogies are great in explaining things but live examples as you furnished are AWESOME...

Some of us are more VISUAL than others and these aids help TREMENDOUSLY...

I will be shooting in [Av MODE] quite regularly and only Manual Mode when using a FLASH when my XTi with Kit lens comes in...

What are some of the parameters I should know when shooting in different types of light...

i.e.,...6am?
.........12 noon?
.........3pm ?

In other words just like how you showed on your diffraction example, anything more than f/16 on certain cameras might prove negative results to the user...

ISO and its relationship to Aperture, Shutter Speed, and DOF is a topic that needs a bit more clarification to me in terms of real life shooting...

May I get your take on this subject, please?

I understand the basics to this as I've read a lot of info...

But, something is missing in my understanding and would just like to have more clarity...

Anything you could share would be greatly appreciated even if its an abbreviated version...

Coming from you I believe it will have a lot of impact on my present understanding...

Thank you!

Roland

Because of diffraction, it's often best to limit your smallest aperture, roughly to around the following, for each sensor size:

1.6x - f/11
1.3x - f/13
FF - f/16

You can play around with various settings to come up with your own guidelines here: http://www.cambridgein​colour.com …ffraction-photography.htm

Roland, thank you for your kind words. I'm afraid my knowledge of photography is not extensive - I've only been shooting seriously for the last 18 months, although 30 years on and off in total, but like you I have a thirst for knowledge and enthusiasm to learn. Where I feel I can help others I shall certainly try. Sometimes I would like to know the answers to questions myself

My background is in IT and I have a very logical mind, so elements of photography that are more logical, technical and mathematical I can understand quite easily. So things like figuring out DOF and exposure (especially with a histogram) are quite easy. This is my well developd left brain at work.

The creative aspects of photography - visualisation, understanding lighting and so on are subjects I still need to understand and become comfortable with. This is my weaker, less artistic, right hand brain letting me down.

You have to remember that mostly there are no absolute rules in photography. There are guidelines, which help you start from the right place, but if photography was as simple as following strict rules from a book we would all be as good or as bad as each other. The skill and artistry comes from our interpretation of those guidelines. For example, as Bryan Peterson says, there is no "correct" exposure as such, it's really just getting the exposure as you would like it in order to portray the scene as you wish others to see it.

Let's take as an example your question above - "What parameters should I know to shoot at 06:00 or 12:00 or 15:00?". I don't think there is any way to answer that question meaningfully without knowing so many more things. For example....
- What is your subject?
- What is the setting for your subject?
- In what direction is the light falling on your subject? - from above/beside/behind/he​ad on? Do you have the option to change that?
- Is the subject large or small? Can you use a reflector to bounce light back onto the subject?
- Is the sky visible in the frame?
- Is there snow, or bright lights, or reflections off water?
- Are you indoors (big or small windows?) (north/east/south/west facing windows - one or more of those)
- Are you outdoors (what's the weather like?) (is the subject in direct sun or in shade?)
- What colour is the light?
- Do you want to emphasise the colour or diminish it?
- Is the subject moving? How do you want to portray (or freeze) motion?
- Is "now" a good time to take the shot, or should you wait for better conditions, either later today or maybe tomorrow or next week? Do you have that luxury to chose?
- What mood do you want to create?
etc. etc.

Here are some recent threads I have contributed to. I believe people found my advice to be helpful. Perhaps you can also learn something from my comments. I'm afraid I don't have answers for everything though

https://photography-on-the.net/forum/showthre​ad.php?t=449936

https://photography-on-the.net/forum/showthre​ad.php?t=449890

https://photography-on-the.net/forum/showthre​ad.php?t=447510

https://photography-on-the.net/forum/showthre​ad.php?t=450073

https://photography-on-the.net/forum/showthre​ad.php?t=448059

https://photography-on-the.net/forum/showthre​ad.php?t=450259

https://photography-on-the.net/forum/showthre​ad.php?t=453262

https://photography-on-the.net/forum/showthre​ad.php?t=448058

https://photography-on-the.net/forum/showthre​ad.php?t=445912

https://photography-on-the.net/forum/showthre​ad.php?t=444708

https://photography-on-the.net/forum/showthre​ad.php?t=404223

https://photography-on-the.net/forum/showthre​ad.php?t=446301

I think that should be enough to be getting on with. It may well be a good idea to hang out in the Critique Corner forum. Of course you can post your own photos and ask for advice or just see what people are saying about other people's work. In the same way that you found my examples on diffraction helpful, it is often easier to offer advice when presented with a picture for critique rather than just talking in general terms about what to do in certain situations.

tdodd,

I really appreciate you posting that here also, as you said maybe others could benefit as well instead of PM's...

I understand that no one knows everything and you are a great man and humble enough to share the TRUTH with us all...Even in my trade as a LANDSCAPE DESIGNER for over 20 years I don't know everything and always enjoy learning!

So I understand where you are coming from with your OPEN attitude instead of the self-professed gurus that mark society and I respect you for that...

All I know is in this thread you have threaded many pieces of the puzzle I had while reading because of your explanations and picture/examples...

I'll learn to observe the variables in my shots and learn to manipulate my shots to creatively capture my images...

As you said to many variables here and weren't these rules made to be broken, hence the guidelines...

Thank you for your advice and comments!

Roland

tdodd,

I've learned a lot in seeing your examples especially the tree...

I will start doing these types of experiments when my equipment comes in using the Kit Lens as it will give me a greater understanding in various settings...

I'll set up my tripod and photograph various subjects at different distances in a variety of light conditions using a 2-second timer to eliminate any vibration from me...

I'll choose Av Mode...

I'll run each sequence as you did right up the aperture values...

Will try at a different ISO after a complete sequence...

This should generally give me a better idea of how this baby works and some foundation and basics before trying to get CREATIVE...

Thanks again for the help!

Roland, It's great to see that you are keen to learn and practice for yourself. There's nothing quite like taking control yourself and seeing the results with your own eyes.

However, while not wanting to see you take too much on board at once, and confuse yourself, do appreciate that Av mode is only one option. If all you're interested in is portraits, landscapes and still life then Av (or manual) is surely the mode to use. But if there is anything with movement - sports, dancing at a party, a flowing stream or waterfall - then you need to pay equal or more attention to shutter speed. Ideally you will pay attention to both, and the ISO setting you need to get the aperture and shutter speed you want. In some situations manual will actually be the easiest mode of all to use.

Have a look at this post - https://photography-on-the.net …hp?p=4869991&po​stcount=39 - in one of the threads I linked to earlier. I go into more depth on linking aperture, shutter speed and ISO together, and why manual mode cn sometimes be the best of all (even/especially for a beginner).