Photography forum: How I learned about f-stops

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Name: Dirt
(Zone 5b)
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dirtdorphins
Sep 21, 2014 9:47 PM CST
Frustrated by my inability to produce pictures of some pretty flower where all of it was in perfect focus I asked, innocently enough, "how do I get the whole thing in focus?" and then I got a lesson about how cameras work, in some kind of practically foreign language and a demonstration.
At this point, I actually do understand much better than I can articulate, so I will share with you the demonstration because it was extremely valuable to me in learning to understand the language used to describe how cameras work.

Here is the set up: 14 batteries arranged diagonally across a table spanning about 13 inches
Thumb of 2014-09-21/dirtdorphins/ca8a03

Here are photographs of the batteries at a 45degree angle coming straight across the table from about two and a half feet away from the center of the line of batteries. The only variable manually manipulated is the f-stop (The camera is auto-adjusting the other parameters accordingly; auto focus in the center; ambient light/no flash; tripod mandatory for experiments like this!)

Note that the depth of field increases, or that the entire line of batteries will come into focus as the f-stop increases

Thumb of 2014-09-21/dirtdorphins/92a332 f/5.6; 1/15sec; ISO-800

Thumb of 2014-09-21/dirtdorphins/7e16da f/10; 1/5sec; ISO-800

Thumb of 2014-09-21/dirtdorphins/d83efc f/20; 0.8sec; ISO-800

Thumb of 2014-09-21/dirtdorphins/01f758 f/29; 1.6sec; ISO-800

Thumb of 2014-09-21/dirtdorphins/e190c9 f/40; 3sec; ISO-800

Note also that the ISO is relatively 'fast' and constant-- the light was low and the camera was trying to minimize exposure times by using the upper end of its preset bracket. The bracket was preset at 100-800 to avoid graininess.
Most importantly, check out those increasing exposure times with the increasing f-stops and ask yourself how long you can hold a camera perfectly still. I can hold still for about 1/250sec if I don't breathe...
Honestly, I blame the wind and I blame the cats (both are to blame on occasion), but 99.9% of my unfocused pictures are either because I moved (I don't lug the tripod around the yard) or because I actually focused in front of or behind my subject somewhere...

The same principle applies for close up shots as well, but the really confounding thing is that the closer you are to the subject the more compressed the field becomes such that the area that is in focus with a particular aperture/time/sensitivity combination is necessarily a smaller 'slice' of the whole.
Here again, with the ruler now, looking down at it from about a 30degree angle and closer to it (about 15 inches away)
Thumb of 2014-09-22/dirtdorphins/1299c3 Thumb of 2014-09-22/dirtdorphins/821831 Thumb of 2014-09-22/dirtdorphins/fac406 Thumb of 2014-09-22/dirtdorphins/b98b7e Thumb of 2014-09-22/dirtdorphins/0177ed Thumb of 2014-09-22/dirtdorphins/b131b1 Thumb of 2014-09-22/dirtdorphins/02c117
the dust specks, numbers, hash marks, and scratches on the table are all in focus at about the 10 and 1/2 mark with f/5.6 in the first photo and in each subsequent photo with increasing f-stops (and, necessarily, exposure time) more of the whole comes into focus - both in the foreground and in the background. If the photos were taken exactly perpendicular to the table and ruler then everything would have been in focus because it's all in the same plane with no foreground or background.

But plants are, of course, three dimensional...so it's good to figure out what you want to focus on and how big of a slice you need in focus (versus how long you can hold still).
Thumb of 2014-09-22/dirtdorphins/4c326e f/13; 1/400sec; ISO-200
And then there is the ever important consideration of background. Sometimes it can be very critical to blur the neighbor's boat, for example, into a non-distracting, unrecognizable assortment of color and texture with a shallow depth of field.

Name: Lynn
Dallas, OR (Zone 8b)
Charter ATP Member Garden Sages I helped plan and beta test the plant database. I helped beta test the Garden Planting Calendar I was one of the first 300 contributors to the plant database! Plant Database Moderator
Forum moderator I helped beta test the first seed swap Celebrating Gardening: 2015 Plant and/or Seed Trader Garden Ideas: Master Level Sempervivums
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valleylynn
Sep 22, 2014 11:36 AM CST
I will have to keep reading through this bit by bit, and playing with my camera, for it to connect usable information in my brain. It is starting to sink in.
Time to play with my camera.

I took this photo a few years back. I don't know what I did to get the background darkened, and the leaves and some blooms clear. But lots of the blooms are over exposed. .Sony Cybershot ISO-100, f/5.3 Exp. 1/320 sec.
Thumb of 2014-09-22/valleylynn/28f45d

It seems that I had much better luck with the little Sony than I do with my Nikon D40.
Name: Asa

Bee Lover Garden Photography Region: Utah Garden Ideas: Master Level Photo Contest Winner: 2016
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evermorelawnless
Sep 22, 2014 5:28 PM CST
dirtdorphins said:
And then there is the ever important consideration of background. Sometimes it can be very critical to blur the neighbor's boat, for example, into a non-distracting, unrecognizable assortment of color and texture with a shallow depth of field.


Yep. The first picture, shot at f/6.3 has a nicely obscured, non-distracting background. The second, shot at f/45, tells the en-tire story...and is...well, a throwaway for that reason.


Thumb of 2014-09-22/evermorelawnless/e4263a Thumb of 2014-09-22/evermorelawnless/db3baf

Also notice that slice or chunk of what's in focus - in the case of the first picture, the foreground and background are blurred to a degree and the focus (unfortunately) is on the backmost petals of the centered blossom.

Tip: (that I didn't follow here): If you're having problems with focus (and that could be an artifact of your camera or lens), select a slightly bigger chunk (increase the f-stop number) of stuff that will be in focus...and then focus on something that's slightly in front (nearer to the lens) of the part of the subject that you need to have in focus.
I share this blog with the unwashed cetacean - have a look! - http://garden.org/blogs/view/evermoredorphins
Name: Asa

Bee Lover Garden Photography Region: Utah Garden Ideas: Master Level Photo Contest Winner: 2016
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evermorelawnless
Sep 23, 2014 7:49 PM CST
valleylynn said:
It seems that I had much better luck with the little Sony than I do with my Nikon D40.


If this reply gets a little wooooo-spooky-outthere-esoteric, forgive me...

And...this is probably not the right place to start this discussion...but...maybe I or someone can make a thread on the subject.

Preambles out of the way, a note on cameras (and even lenses) is in order: In my experience every camera brand and every camera has its own personality. Although each camera is doing more or less the same thing (exposing a photo-sensitive medium to light), the way that medium (and even the medium itself) varies from camera model to camera model.

Maybe it would help to think of it this way. Imagine that you had a pile of napkins and you asked 100 people to each fold a napkin for you. You'd end up with 100 folded napkins, but how the napkins were folded and how neatly they were folded would vary by napkin folder. With cameras, it's similar. If you had 100 digital cameras, set all to "automatic", and shot the same subject from the same distance -- I contend that you'd end up with 100 different photographs. Some radically different.

The reason for this, of course, is twofold. First, the cameras themselves are different physically. They have different optics (glass), different photo sensors, and different physics, generally. Second, digital cameras are really computers, so the firmware (think software or program) varies from brand to brand and camera to camera - and necessarily approaches the same problem somewhat differently from its peers -- which obviously will yield different results.

But I would contend that if you took the time and fiddled with some of the settings (and necessarily the more obscure ones), you could probably approximate the same photograph with all 100 cameras.

That said, I think that your D40 is superior to the Cybershot in almost every way. I *think* the trouble that you're running into when comparing the two is that the Cybershot is making better guesses about how to fold that napkin (take a shot) to your liking than is the Nikon. So that means that you need to figure out how to tell the Nikon to fold that napkin to your specs.

Practically, I think a couple of things are going on (here I'm mostly guessing about what you like about that shot and how you hope to make your Nikon behave): 1): Your Sony thought/thinks about light in a little bit different way from how your Nikon does (either inherently - which is probably true to a degree) or with certain, default settings (generally), and 2) that photo that you posted was lit from the back/side in a way that the background wasn't. That is to say that part of the reason that you took the photograph in the first place (I'd guess) is because its lighting/composition/effect asked you to - that there was something inherently interesting about how that bunch of flower was lit (or, if you're like me, maybe you just blind-pigged it and found an acorn in that shot ;).

But the real deal here, it seems to me, is that your Nikon is frustrating you a little - and I'd assert that's a function of the settings rather than the camera itself. So...this is what I suggest:

Shoot - I just read the manual and a bunch of stuff about the camera - seems that the light metering on it is a little wonky and it could get a little bit complicated to sort out...so... I think the best play would be to post and describe a couple of photographs that didn't come out the way that you imagined them - and maybe I can make a couple of suggestions vis a vis the camera-specific settings.

In the mean time, please have a look at Dave's thread on metering, mine on light, and the stuff about depth of field in this thread. Having an overview on the ideas that are discussed in those threads is gonna be key to making your Nikon obey your will - or at least fold your napkins more like you want them folded.
I share this blog with the unwashed cetacean - have a look! - http://garden.org/blogs/view/evermoredorphins
[Last edited by evermorelawnless - Sep 23, 2014 7:49 PM (+)]
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Name: Lynn
Dallas, OR (Zone 8b)
Charter ATP Member Garden Sages I helped plan and beta test the plant database. I helped beta test the Garden Planting Calendar I was one of the first 300 contributors to the plant database! Plant Database Moderator
Forum moderator I helped beta test the first seed swap Celebrating Gardening: 2015 Plant and/or Seed Trader Garden Ideas: Master Level Sempervivums
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valleylynn
Sep 23, 2014 9:33 PM CST
Thank you evermorelawnless. I will check out those two threads tomorrow, when I am rested and my mind will work better.
Name: Dave Whitinger
Jacksonville, Texas (Zone 8b)
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dave
Sep 28, 2014 7:38 AM CST

Garden.org Admin

I took some photos this morning and shot this Crepe Myrtle 'Natchez' using two different aperture settings. Everything else was identical:

Thumb of 2014-09-28/dave/2ebf52
f/20

Thumb of 2014-09-28/dave/5d0aa2
f/5.6

Notice the background change as the aperture opened up.
Name: Asa

Bee Lover Garden Photography Region: Utah Garden Ideas: Master Level Photo Contest Winner: 2016
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evermorelawnless
Sep 28, 2014 7:47 AM CST
dave said:I took some photos this morning and shot this Crepe Myrtle 'Natchez' using two different aperture settings. Everything else was identical:

Notice the background change as the aperture opened up.


Cool photos, Dave.

Now, the next step in this progression is to take identically framed photos at f/5.6 and f/20 from different distances (too rainy here to do it right now) and notice how the depth of focus changes (thins as you near the subject) and the bokeh characteristics necessarily change, too.
I share this blog with the unwashed cetacean - have a look! - http://garden.org/blogs/view/evermoredorphins
Name: Asa

Bee Lover Garden Photography Region: Utah Garden Ideas: Master Level Photo Contest Winner: 2016
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evermorelawnless
Sep 28, 2014 8:21 AM CST
dave said:I took some photos this morning and shot this Crepe Myrtle 'Natchez' using two different aperture settings. Everything else was identical:

Notice the background change as the aperture opened up.


This is probably a little pedantic and inconsequential, but I think it's important on at least some level to note that when you change the aperture value either the shutter speed or the ISO value (or both) need to change to get a similar exposure.

And that's what happened here, too:

f/5.6, ISO 100 , shutter speed 1/200
-vs.-
f/20, ISO-500, shutter speed 1/83
I share this blog with the unwashed cetacean - have a look! - http://garden.org/blogs/view/evermoredorphins
[Last edited by evermorelawnless - Sep 28, 2014 8:27 AM (+)]
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Name: Ronnie
Southeastern PA (Zone 6b)
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luvsgrtdanes
Sep 28, 2014 9:40 AM CST
Big difference Dave, especially good for flower close ups that the focus is just the flower. I like that with my morning glory photos.
It happens in a flash, but the memory of it last forever. It can not be borrowed or stolen, and it is of no earthly good until it is given away. So if in your hurry you meet someone who is too weary to smile, leave him one of yours, for no one needs a smile quite as much as he who has none to give...

Name: Dave Whitinger
Jacksonville, Texas (Zone 8b)
Charter ATP Member Region: Texas Master Gardener: Texas Permaculture Raises cows I was one of the first 300 contributors to the plant database!
Garden Ideas: Master Level Beekeeper Garden Sages Avid Green Pages Reviewer Celebrating Gardening: 2015 Plant Identifier
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dave
Sep 28, 2014 10:33 AM CST

Garden.org Admin

Pedantic is good, evermorelawnless. Thanks for pointing out the other changes to the images.

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