When metering off the sky, is it important to have the aperture wide-open?

[greg_w]

I'm reading the book "Understanding Exposure," and there's something I don't understand. The author describes several situations where metering off the sky is the best option. He usually starts with a wide-open aperture, figures out the correct shutter speed, and then adjusts the aperture to the desired setting (which requires re-adjusting the shutter speed). Why not just start with the desired aperture? Is there some advantage to metering with a wide-open aperture?

~Oops. I put this in the wrong forum. I'm going to ask it again in the "Talk About Photography" section.

[In2Photos]

No, you can start at your desired aperture since the physical size of your aperture will not change until you press the shutter or DOF preview button.

Perhaps he does this to get you to stop and think about your settings before shooting. If you get in the habit of resetting your camera before each shot and then adjusting the settings for each situation, you are less likely to use the wrong settings.

[tonylong]

That may have been a holdover from the days of manual cameras/lenses (he wrote the first edition of the book prior to digital photography, so it may have been referencing manual cameras as well).

Automatic exposure systems take meter readings at wide open apertures so it doesn't matter what your initial settings are.

[40Driggs]

Good post. I read the same book and had the same question after finishing. On another note, I would recommend this book highly for a beginner like me. I really feel like I learned a lot. I would also recommend the 40D guide by David Busch for all of you 40D owners out there.

[Alexajlex]

Portrait work where you want a shallow DOF (or any kind of work where you need subject isolation).
Then again you say that he changes the ap and stops down on it so at this point I guess he decided to shoot landscapes instead :)

As far as what the book says I don't see any benefit to having the ap wide open and then tweaking the shutter then having to change the ap again.

Besides if you are outdoor shooting landscapes or the sky you should be able to get a few things dialed in right of the bat (stopped down ap f16, ISO 100) then all you have to mess with is the shutter.

Sunny 16 rule can be a good starting point for outdoor landscape work (and adjusting accordingly for different light conditions).

ISO, shutter, aperture, all have an effect on exposure.

There is no right or wrong way to choose your main leading setting and then adjust all the others around that.

The main thing that will decide what you are adjusting will be what you are taking pictures of.

Panning cars to blur the background for example will require a shutter around 160-250.

For a portrait you may want to start @ f2.8-3.2 and adjust the ISO and shutter around that.

[Wilt]

Peterson mentions the Pentax Spotmatic in his book. It was a 'stop down' metering camera...when you turned on the meter, the lens stopped down to the aperture selection automatically, so that you could meter the scene at that aperture. That would be why he would set the lens to wide open.

I hate it when people write things in the context of older equipment that behaves unlike any of the cameras of today, and fail to update the text accordingly to what the modern reader can comprehend!

[mangaloreaviators]

I have read about the Sunny Rule 16, I use a XTI. When ever I do Landsacape, I choose Manual Mode, Set the Aperture to F22with my 18-55 IS Lens.

I use the DEF Preview button to check the Depth of Field...all I see is the View finder dims for a second and then back to normal.

How would one guess what F Number to choose if the DEP button is not available.
I know people use F22,16 as they consider that as the best.

Please help me understand this concept.

I use the Sunny Rule 16 concept when I do Landscape Photography
F16@ ISO 100 SS 1/100
F22 @ ISO 100 SS 1/60

I do this give and take calculation during this.
Close Aperture- Decrease Shutter Speed and Vice Versa. The last resort is ISO.
I also make sure I use Tripod when ever possible irrespective of what shutter speed I'm working on.

[greg_w]

Thanks everybody. Mystery solved!

It's a great book, but it seems pretty clear that the revised edition still has some obsolete information. In addition to this issue, he also talks a lot about focusing using the distance scales on the lens. I was struggling with that too, and it seems like that doesn't work very well with modern lenses (and is mostly unnecessary with improvements to autofocus systems).

[Hermeto]

Thanks everybody. Mystery solved!

It's a great book, but it seems pretty clear that the revised edition still has some obsolete information. In addition to this issue, he also talks a lot about focusing using the distance scales on the lens. I was struggling with that too, and it seems like that doesn't work very well with modern lenses (and is mostly unnecessary with improvements to autofocus systems).

Here is the help for understanding the Understanding Exposure book, written by POTN member Robert_Lay.
Take a look, it’s well worth reading:

http://www.zaffora.com/W9DMK/BryanPetersonUnofficialHelpFile.htm

[PhotosGuy]

Try this, too: First set the f-stop & shutter speed you need. Then adjust the ISO.
Need an exposure crutch? (http://photography-on-the.net/forum/showthread.php?t=89123)

This shows how the subject can affect the exposure & why manual keeps me worry free:
Post #47 (http://photography-on-the.net/forum/showpost.php?p=5191658&postcount=47)

[PhotosGuy]

Duplicate posts are against the forum rules, so I'm merging this with your other thread.

[tzalman]

I have read about the Sunny Rule 16, I use a XTI. When ever I do Landsacape, I choose Manual Mode, Set the Aperture to F22with my 18-55 IS Lens.

I use the DEF Preview button to check the Depth of Field...all I see is the View finder dims for a second and then back to normal.

How would one guess what F Number to choose if the DEP button is not available.
I know people use F22,16 as they consider that as the best.

Please help me understand this concept.

I'm afraid you have been misinformed. f/22 is definitely not reccomended for landscapes with a 1.6 crop camera and even f/16 is questionable. It is best not to go smaller than f/11.

Because of the XTi's dim viewfinder, the DOF button is of very limited utility at f/11 and completely useless at f/22 in any sort of normal light.

Sunny 16 is all very well for sun-lit scenes, but what do you do if a cloud comes along? Or late in the day or early morning? Or in the shadows? Use your meter. You paid for it and used properly it is a good tool. Sunny 16 was used 50 years ago before cameras had meters.

[tdodd]

Sunny 16 does have derivitives, which aren't quite so catchy to remember....

http://medfmt.8k.com/mf/sunny.html

http://www.fredparker.com/ultexp1.htm

I find it very helpful to be aware of Sunny 16, as a starting point when figuring out manual exposures. Of course, my palm comes in pretty darn handy too :)

I have to agree, the use of f/22 should be used with caution on crop bodies with high pixel density sensors. I try to make f/16 my upper limit, but keep it lower if poss.

[mangaloreaviators]

Tzalmann and Tdodd- I have been using F16 and F22 for Landscape all these days. I have around 35 images till date.

Is there any reason why we should not use F16 and F22 on cropped sensor?

I have ordered 2 books recently from USA. Understanding Exposure and Slow Shutter Speed by Bryan Peterson. I will read them and see what knowledge it gives me.

[tdodd]

I shot a series of test images to demonstrate the problem. Album here....

http://picasaweb.google.co.uk/EezyTiger/POTNDiffractionTestWithFStop?authkey=zi1h_3k1k0s

I don't print my photos but I do view and display them as 50% crops on a 40" 1920 x 1080p LCD TV. I prefer to lose a little sharpness close up and in the distance, with a pin sharp focus point, rather than have the entire photo soft throughout.

Lens test results put some science into the argument....

http://www.photozone.de/Reviews/Canon%20EOS%20Lens%20Tests/181-canon-ef-s-18-55mm-f35-56-is-test-report--review?start=1

Your lens is sharpest, with least CA, at around the f/5.6 - f/8 mark.

At 55mm and f/8 the hyperfocal distance is 65.5' and you can have everything in focus from 32.7' to infinity
At 55mm and f/11 the hyperfocal distnace is 46.3' and you can have everything in focus from 23.2' to infinity
At 55mm and f/16 the hyperfocal distnace is 32.8' and you can have everything in focus from 16.4' to infinity
At 55mm and f/22 the hyperfocal distnace is 23.3' and you can have everything in focus from 13.6' to infinity

Maybe there is a use for f/22 and more, but at what cost?

[In2Photos]

Tzalmann and Tdodd- I have been using F16 and F22 for Landscape all these days. I have around 35 images till date.

Is there any reason why we should not use F16 and F22 on cropped sensor?

I have ordered 2 books recently from USA. Understanding Exposure and Slow Shutter Speed by Bryan Peterson. I will read them and see what knowledge it gives me.
Yes. It is called diffraction. The short of it is that the images will soften due to diffraction. There are a few threads on POTN about the subject, some are pretty lengthy!

[mangaloreaviators]

I stubled upon this article and this created further confusion.
http://www.dpchallenge.com/tutorial.php?TUTORIAL_ID=49

In this article, Photographer uses F4 and F3.5 for Night Photography. Are't we supposed to have a small Aperture like F11 or F16 as we were discusing.

[tonylong]

I stubled upon this article and this created further confusion.
http://www.dpchallenge.com/tutorial.php?TUTORIAL_ID=49

In this article, Photographer uses F4 and F3.5 for Night Photography. Are't we supposed to have a small Aperture like F11 or F16 as we were discusing.

First, the "best" aperture is in the mind of the photographer! If you take the time to learn about how various apertures affect your photo, then you decide for yourself what you want the outcome to be.

For the night shots, it sounds like it's possible that the ones taken at wide apertures were hand-held. Not certain, of course, but that would be a strong possibility. If the subjects of interest were in the depth-of-field range, such as a city skyline, you could still get things in focus. On a tripod, of course, you can use a narrower aperture for max DOF.

With landscape photography, you can get by with, say, f/11 as long as you don't have foreground objects that need to be sharp as well as distant background objects. Bearing in mind that with a crop (small pixel site) camera diffraction begins to be a concern narrower than f/11, only you decide what is best for your image.

Yes, plenty of pro landscape-type photographers have produced great shots at f/22, which is too narrow to escape diffraction for full-frame shooting. There is a time when you sacrifice one quality of an image for another. But you have to learn how to make those tradeoffs!

[monochrome]

I just finished the book tonight. I got the impression that he did this on very low light situations where the shutter speed at his desired aperture might be over 30 seconds. He starts out wide open to get the overall exposure, then closes down to his desired aperture and adjusts the shutter speed. If by chance the calculated shutter speed is in the bulb range, he knows how long to hold it open. If the desired shutter speed is not in the bulb range he sets it and takes the shot. Maybe I read too much into it.

[tdodd]

I stubled upon this article and this created further confusion.
http://www.dpchallenge.com/tutorial.php?TUTORIAL_ID=49

In this article, Photographer uses F4 and F3.5 for Night Photography. Are't we supposed to have a small Aperture like F11 or F16 as we were discusing.
With your lens at a wide angle setting you get a quite phenomenal DOF at almost any aperture. In my earlier post the examples I gave were worst cases for your lens, as far as DOF is concerned, by choosing the telephoto end of your zoom range - 55mm. If you shoot at the wide angle end - 18mm (which in the range that article talks about - then you can shoot with much larger apertures and still get everything in focus. I don't agree at all with his advice to focus in the far distance, because focusing at 15' will get far more in focus than focusing at 400' or something.

If you shot at 18mm and f/4 and focused the camera at 15' - about 4.3m - you would have everything in focus from around 8' away to infinity.

This example is taken from the http://www.dofmaster.com/dofjs.html website. Go to the website and have a play around with some of the variables and see how DOF gets affected. For any combination of focal length and f/stop, have a look at the hyperfocal distance on the right hand side. That is a "special" distance that will keep everything in focus from as close as possible while also keeping things at infinity also in focus. For the landscape photographer it can be a very handy thing to know.

Look at the figures I've also attached for a 10-22mm lens at 10mm and wide open (f/3.6 actually, because I can't pick f/3.5 on the website). If you focus at ~5' away you can get everything in focus from 2.5' to infinity - with the lens wide open! At 10mm you really don't need f/22! In fact, you may as well use the aperture that gives the sharpest images over all. Looking at the figures here - http://www.photozone.de/Reviews/Canon%20EOS%20Lens%20Tests/174-canon-ef-s-10-22mm-f35-45-usm-test-report--review?start=1 - it looks like around f/5.6 - f/8 is around the optimum.

So, with wide angle lenses, your choice of aperture has very little impact in terms of DOF - you will get lots and lots of the scene on focus, whether you want to or not. But the aperture still has a purpose in terms of helping you have more options for shutter speed. You can open up the aperture and keep fast shutter speeds, to freeze motion and camera shake, or close down to get longer shutter for creamy smooth stream and waterfalls or long trails of vehicle lights at night, for example. So for wide angle your creative choices are more about shutter speed than aperture. Aperture just helps you use the shutter speed you want.

[mangaloreaviators]

I shot a series of test images to demonstrate the problem. Album here....

http://picasaweb.google.co.uk/EezyTiger/POTNDiffractionTestWithFStop?authkey=zi1h_3k1k0s

I don't print my photos but I do view and display them as 50% crops on a 40" 1920 x 1080p LCD TV. I prefer to lose a little sharpness close up and in the distance, with a pin sharp focus point, rather than have the entire photo soft throughout.

Lens test results put some science into the argument....

http://www.photozone.de/Reviews/Canon%20EOS%20Lens%20Tests/181-canon-ef-s-18-55mm-f35-56-is-test-report--review?start=1

Your lens is sharpest, with least CA, at around the f/5.6 - f/8 mark.

At 55mm and f/8 the hyperfocal distance is 65.5' and you can have everything in focus from 32.7' to infinity
At 55mm and f/11 the hyperfocal distnace is 46.3' and you can have everything in focus from 23.2' to infinity
At 55mm and f/16 the hyperfocal distnace is 32.8' and you can have everything in focus from 16.4' to infinity
At 55mm and f/22 the hyperfocal distnace is 23.3' and you can have everything in focus from 13.6' to infinity

Maybe there is a use for f/22 and more, but at what cost?

Tdodd I did not check this post. Thank you very much for doing all the test to explain why I should not be using F16 and above on a cropped camera.