No more details/focus past f/16?

DJBee49 · June 2013

Just building on Msmoto's posts - it is normal when using 4X5" cameras in studio, especially for close up work such as jewellery shots, to use apertures as small as f45 and even f90. With the 'standard' lens for 4X5" cameras having a focal length of 150mm (and 200mm - 300mm lenses commonly used), very small apertures and expert use of movements on monorail cameras is the only way to achieve critical sharpness. When you get everything right, the results are truly astounding. Not easy though!

The f64 group used 10X8" cameras for the most part and were forced to use such small apertures and camera movements for the same reasons, except with 10X8s, it is much harder! The 'standard' lens for a 10X8" camera is 300mm - with the same limitations on depth of field as this focal length demonstrates on any other camera.

I am not an expert on optical design but you are obviously dealing with different parameters here, as a lens designed for a 4X5" camera not only has to cover the 4X5" format but also the off-axis movements of the camera's movements. In other words, it must project a sharp image onto an even larger area at the focal plane than the film/sensor size. Presumably, the designer of such a lens builds into this design a minimal amount of sharpness deterioration as a result of diffraction effects, knowing that such apertures would inevitably be used as standard practice.

TaoTeJared · June 2013

I think everyone is circling around the concept that:
Optimum Focus is not the same as Optimum Sharpness.
An image can be in focus (think of a mountain landscape with the focus of the closest object being 1000's of meters away) and could be easily shot at f11-F22 with no noticeable issues. It is all in focus and looks "correct."

Sharpness pertaining to this discussion in my experience, comes into play when the primary focused object is in the foreground and wanting the background in focus.
(This is the best I had on hand without digging in archives)
_STD8485

Shot at F/11

The crane is sharp, the treeline less so but the whole image is in focus.

If I shot that at F32 diffraction would have caused the front subject to not be as sharp as it could be. At that point I dropped the f-stop closer to optimum sharpness but wanted whole image in focus. F11 was the compromise.

This Image I wanted all the detail so I shot at optimum sharpness: f/5.6
_LST8535

And some images, optimum sharpness doesn't matter as long as you got focus (f/8 fisheye)
_8001732

Ade · June 2013

An image can be in focus (think of a mountain landscape with the focus of the closest object being 1000's of meters away) and could be easily shot at f11-F22 with no noticeable issues. It is all in focus and looks "correct."

Mathematically we can show that a D800 shooting any lens at f/22 would be so diffraction-limited that its effective resolution drops to less than 5 megapixels, using green wavelength as a reference point. I would say that is "noticeable" given the 36mp sensor.

TaoTeJared · June 2013

Ade that is plain BS unless you are planning on using a Holga converted lens. You do math like every analyst the I worked with who got fired - decide the result and then modify and choose the math to prove it. It's plain sickening and completely transparent.

Enough on the attacks on me on every single thread I post something too. No one finds it humorous or remotely amusing.

JJ_SO · June 2013

It's your replies that belong in the "Not remotely amusing or humorous"-category. If nothing else helps you complain about being attacked - not realising your kind of attacks.

Ade · June 2013

When people make bizarre claims not supportable by facts, I tend to speak up.

Anyway, for a good introduction into the science behind diffraction limits to resolution, see:

http://www.luminous-landscape.com/tutorials/resolution.shtml

Refer to Table 3: "Number of pixels of optimal size for different apertures of a diffraction limited lens"

Note that in the table, for 35mm full frame sensors at f/22 for green light (0.55 microns), the effective resolution is down to 4 mp.

(Green light is chosen because it is the dominant wavelength for human vision).

Msmoto · June 2013

My experience suggests another factor in diffraction is the ratio of light to dark in the scene. On a recent sunset, the sun was behind a building and there was clearly a diffraction process occurring and when the sun finally set the diffraction went away to a great extent. This was at f/20 on a 400mm f/2.8 with TC-20EIII behind it and a dark red filter. My guess is the limiting of the color wavelengths with the filter may have actually improved the sharpness. The question is really whether this phenomenon was diffraction or flare and how one can tell the difference. Or if there actually is a difference practically speaking.

In this image the building is over one mile away.

http://www.flickr.com/photos/fantinesfotos/8954532251/sizes/o/

DJBee49 · June 2013

Ade. Very interesting (but complicated!) article illustrating just how complex the whole affair actually is.Thank you for pointing us all to it. I have listened for many years to all the discussions about what actually constitutes sharpness, DOF parameters, circles of confusion etc. and some time ago decided to just get decent lenses, use good technique, build up my shooting knowledge and make images that look sharp to me where I wanted them to be so! It seems to have worked for the most part.

Msmoto. Interesting image. Two other factors that might be relevant are, of course, atmospheric particles and the refractive effects from density ripples in the air due to heat rising. I use a telescope quite a lot for ornithology and this (heat haze) is a major factor in how sharp (whatever that may be!) the image looks. In fact it often far outweighs the effective quality of the lens, making my excellent Nikon 'scope no better than a relatively poor, much cheaper example. Happily, not always though and living in England, of course, we rarely get any heat to make a haze anyway!

Perhaps your red filter was also a help here as the blue and to a lesser extent green wavelengths are, I think, the most effected by particle reflection (I know it depends on particle size but in general) and their transmission would have presumably been much reduced.

Ade · June 2013

@Msmoto @DJBee49: good points about possible effects from diffraction, particles and heat haze.

When I look at the image, my first thought is maybe the image didn't require f/20 at ISO 640. Opening up to (say) f/11 or wider might have doubled the potential sharpness of the image, subject to the above conditions.

On the flip side, even a degraded image with "just" 4-megapixel effective resolution still has enough detail to make a good quality 8"x10" print (> 200 dpi) -- maybe a very good quality print with some careful post processing.

So it's easy to take pictures at very small apertures like f/20 or f/22 and conclude that all is well, since the prints may still come out ok. However, the full potential of the camera is not being used, and problems like softness and artifacts may appear when printing at larger sizes.

With modern cameras & lenses, understanding the effects of diffraction and setting the appropriate aperture is part of "using good technique" -- on par with using a tripod, mirror lock-up, cable release, etc.

SquamishPhoto · June 2013

Ade that is plain BS unless you are planning on using a Holga converted lens. You do math like every analyst the I worked with who got fired - decide the result and then modify and choose the math to prove it. It's plain sickening and completely transparent.

Enough on the attacks on me on every single thread I post something too. No one finds it humorous or remotely amusing.

You completely denigrate the guy in one sentence and then almost breathlessly in the next sentence you admonish him for what you oddly perceive as attacks. Having the humility to know when you're wrong is a quality worth aspiring to, as is avoiding hypocrisy in your own writing.

Vipmediastar_JZ · June 2013

All of this thecnical info is great to know. It comes in handy to improve our shooting. But in all honesty the extreme technical stuff gives me a headache and takes the fun out of photography.

I work in the IT field as well and I understand software and hardware very easily.

Self teaching myself photography has been taking a long time but it's part of the challenge in becoming a great photographer.

For education purposes I started to read this article http://en.m.wikipedia.org/wiki/Depth_of_field
but got a headache. Lol

lots of Info but I prefer the learning experience by making mistakes and learning from posts like these even though I have a headache.

Msmoto · June 2013

Let us all try to discuss the issues and not the personalities....please.

Re: My sun photo.... a few of the problems were trying to focus looking at the sun directly with only a 3 f/stop red filter in front of me and 800mm out front. I tried manual and auto, but was attempting to try and figure if there was possibly more infrared coming in than I could see, and hoped I was able to obtain a little DOF to cover this...by stopping down to f/20. The effective max was f/5.6 so I was down 4 stops. This was my first attempt at shooting the sun behind an object over a mile away and learned a lot. The sun was moving laterally so quickly on my first outing I was running down a country road carrying the tripod, gimbal, w/ 400 and D4 on top.....humorous for the observers....

And, as I have discovered from my astrophotography friends...the limiting factor is the garbage in the atmosphere. My direct sun shot in mid day is here for anyone interested....

http://www.flickr.com/photos/fantinesfotos/8982195512/sizes/o/

Shot at f/16...3 f/stops down, ISO 100, Front filter decreasing the light by 99.999% and the dark red in the back. (1/250 sec, VR Tripod mode)

I find this stuff a lot of fun and with a very steep learning curve....LOL

Paperman · June 2013

What are the specs in the middle ?

Msmoto · June 2013

@Paperman

These are the same "specs" the NASA photos have.....called sunspots. The largest is bigger than the size of the Earth. On my first shots of the Sun I thought I had a sensor problem, then looked at the NASA photos
http://climate.nasa.gov/news/878

Howdy, Stranger!

Categories

In this Discussion

Who's Online (0)

No more details/focus past f/16?

Comments