Questons about Aperture(From Understanding Exposure. B.Peterson))

[allendehl]

Hi guys,

Following your recommendations I just bought Bryan Peterson's Understanding Exposure. Its great so far, very well explained but still can't figure out some things.

I'm now in the Aperture section(page 38,39 to be specific) and there are some doubts I hope some of you can help me with.

1- Auto-Depth-of-Field Scale: What is this? I have a Canon EOS Rebel XS and cant find this feature neither in the camera or the manual. If exists..how to use it?

2- "Distance Settings". He talks about it and says it allows you to "preset the depth of field"...can any body tell me where to find it and a little bit about it? He also says that for taking storytelling exposures he doesn't focus the lens at all, he just preset the focus via Distance Settings.

3- "Preset Focus"..in the pics he included he says he "preset the focus so that the distance of two feet is aligned directly above the center mark near the front of the lens"....Totally lost here..don't know how to preset the focus(or what that is) or what he means with the whole sentence.

I know these are quite few questions and probably too specific, but I know some of them are conceptual and in the other hand many of you have the mentioned book so can see better what Im talking about.

Thanks a lot in advance!

[kauffman v36]

you need a lens with a distance scale on it. neither of your lenses have this im afraid, making preset focus, along with the rest pretty useless.

[PhotosGuy]

you need a lens with a distance scale on it. neither of your lenses have this im afraid, making preset focus, along with the rest pretty useless. I agree with the first part, but not the second. Maybe you can't set the distance according to the scale on the lens, but you can use the DOF tables to find the distance you need, estimate where that is in the image, & focus on that spot? Then turn auto focus off on the lens.
See the DOF calculator at the bottom.
Depth of field and aperture selection question. (http://photography-on-the.net/forum/showthread.php?p=2407876)

[SkipD]

Most of what was described there applies to old-school lenses. In the olden days before automation took over and before zoom lenses became so popular, our lenses had both a distance scale and a (usually colored) graphic indication of the expected depth of field for each f-stop setting. The photo here is of my 50mm f/1.4 Nikkor, circa 1967. You can see that the focus is set for 10 feet and the f-stop is set at f/8. The f/8 setting number is in pink. You can see pink lines that show you the approximate depth of field limits for this lens at f/8 and focused at 10 feet.

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[allendehl]

Thanks all!!

Still confusing..:confused:, so in your own words, how would you guys achieve an exposure like the one I'm referring to? (page 39, a field of yellow flowers with a tree at the end). Where you guys decide to focus at? Do you use the central focus point?....The Canon Rebel XS has 7 to choose from.

PD: Mainly those who don't have the DOF meter in the lens.

Thanks

[allendehl]

Also,

Peterson mentions that new SLR Canon cameras has "Auto-Deph-of-Field" Scale. What is that and where can I find it in my camera?...I know I have a button for DOF Preview in my Camera but I dont understand how it works. Is this useful some how to what we are discussing here?

[kauffman v36]

yes, you can use the DOF preview button to see where your DOF is going to lie in the composition. while looking through the viewfinder hold the DOF preview button and the viewfinder will dim and the lens will stop down. what you see when you do that is what the end result will look like. so if something is not in focus that you want to be then change settings accordingly.

and photoguy, i was going to assume the OP did not want to hassle with DOF charts/scales/graphs, of course with those tools he can do the things peterson mentions, just a major PITA.

my advice, use the DOF preview button and you will see where your area of focus lies. adjust accordingly. it is much easier with an old school lens though, lol. good luck

[WaltA]

In my experience, in landscape its not necessary to know the DOF down to the inches (or mm's) especially if your a beginner.
The OP is talking about a field of flowers so as long as you know that F16 will have everything in focus and F4.5 will have only a few feet each side of your Focus Point then you can take good pictures.

The rest is learning through taking gazillions of pictures and testing.

[allendehl]

yes, you can use the DOF preview button to see where your DOF is going to lie in the composition. while looking through the viewfinder hold the DOF preview button and the viewfinder will dim and the lens will stop down. what you see when you do that is what the end result will look like. so if something is not in focus that you want to be then change settings accordingly.

and photoguy, i was going to assume the OP did not want to hassle with DOF charts/scales/graphs, of course with those tools he can do the things peterson mentions, just a major PITA.

my advice, use the DOF preview button and you will see where your area of focus lies. adjust accordingly. it is much easier with an old school lens though, lol. good luck

Hi Kauffman,

Thanks for the DOF Preview explanation.

I think I'm starting to understand, I did some experiments at home and I can see how the DOF Preview works. Basically if I want to shut that field of flowers I just close the aperture as much as I can and then find the correct point to focus on using the preview.

There will always be some blur in the furthest areas from the focus point, so the decision is about where I want these areas to be..closer to the front or to the end of the frame.

I'm I right? Please find bellow the result of my experiments:

f/36, just focusing on the first coin from the front:
http://i492.photobucket.com/albums/rr286/allendehl/IMG_3980.jpg

f/36, just focusing on the 6 coin from the front:
http://i492.photobucket.com/albums/rr286/allendehl/IMG_3981.jpg

f/36, just focusing very close to the quarters tower:
http://i492.photobucket.com/albums/rr286/allendehl/IMG_3982.jpg

Its pretty evident that even with small apertures as the focus point is moving from the front to the bottom the quarters tower gets sharper and the first coin blur.

[kauffman v36]

first off, your first image nothing is in focus, i am going to assume the first coin is closer than the min. focusing distance. i could probably write a whole paper on aperture, DOF, CoC, and how it all corresponds to DOF. the problem is that a given aperture will not have the same DOF at all distances focused. the closer you are focused the less DOF you will have generally at a given aperture. there is a hyperfocal distance (which will confuse you even more) but forget about that for now. f32 focused at 2 feet will give you a DOF thinner than f32 focused at 50 feet...a lot thinner. instead of using a DOF calculator of graph/chart/scale i suggest using the DOF preview button to just check where the focus lies. IMO, you do not need to shoot f32 for anything, i would avoid it as diffraction is already evident. a large DOF when speaking about slr's is f8-f16. and with a crop body you get even a larger DOF, this is why our lenses only go to f22 or f32 where as my MF lenses all go to f32 and large format lenses can have f100 or crazy numbers like that. pm me with questions if your confused. this is probably one of the hardest parts of photography technicality to understand, you have to really udnerstand the concept behind it instead of just listening to the settings people tell you to shoot at.

you can catch a fish for a man and hell have dinner for one night...or you can teach the man to fish and hell have dinner forever. same thing applies here.

-Robert K