Display:
  • Small aperture = bigger depth of field = more of the picture in focus.

  • Long lens = smaller depth of field.

  • Wide lens = bigger depth of field.

  • Effective focal length on D80 = marked focal length * 1.5

  • For hand holding, you need a shutter speed of 1/(effective focal length)

So, 50mm lens, you need 1/75s shutter. 105mm lens you need 1/150s.

  • Close in shake has a bigger effect. Faster shutter for close-ups.

  • Use ISO settings to allow you get your shutter speed up higher.

  • Exifs are the information about the photograph that's embedded in the file. Depending what you use to process your photos you should be able to see shutter speed, focal length and stuff like that.

With practice you can get away with more - I can get a good hit rate holding a stop or two slower than I should be able to , and margouillet's picture below at 1/30 shouldn't be sharp in theory.

Ask for explanations of the other jargonese in there!

by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 05:37:45 AM EST
[ Parent ]
Someone trying to learn who's willing to ask "stupid" questions to extract information from people would be highly useful here!
by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 05:58:59 AM EST
[ Parent ]
Well, I'm not entirely up to scratch with understanding focal length.

Ad astra per aspera
by In Wales (inwales aaat eurotrib.com) on Fri Mar 7th, 2008 at 06:06:56 AM EST
[ Parent ]
That wasn't a question!
by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 06:20:13 AM EST
[ Parent ]
Alright then. What's focal length all about, Colman?

Ad astra per aspera
by In Wales (inwales aaat eurotrib.com) on Fri Mar 7th, 2008 at 06:23:43 AM EST
[ Parent ]
It's the distance from the "optical centre" of a lens to the film. You can think of it as the distance from a pinhole to the film. To understand the effect, put a small (say 1cm) hole in a sheet of paper and look through it.

Really: I'll wait.

The closer you hold the hole, the more you can see of the scene, the further away, the less you see. So, short focal length means a wider angle view, long focal length means narrow angle view.

To illustrate the effect, I'll demonstrate why I do photography rather than drawing: on the left we have a pinhole very near the sensor, so the tree(!) only occupies a small part of  the frame, on the right the pinhole is much further away, so the tree occupies lots of the frame.

So far so good?

Now, where this gets interesting is when you change the size of the sensor the light is falling on:

Three sensors indicated there, for a 60mm focal length: 35mm, the DX sensor in the Nikon digitals and most other digital SLRs and 6x6 film. Digital compacts have much smaller lenses.

If you trace the light you can see that the "house" (or "robot")  is covering most of the 6x6 frame, that only a small part of it is visible to the 35mm sensor and even less to the DX sensor. A compact camera thinks that a 60mm lenses is a long telephoto while a 6x6 sensor sees it as a normal lens and a 4" x 5" would see it as an extreme wide-angle. Thus the 60mm lens on a 35mm is equivalent in angle  of view to a 90mm on the DX sensor.

DId that help?

by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 07:11:23 AM EST
[ Parent ]
In understanding why you choose photography... Yes! LOL

More seriously, great effort, you must have a scan nearby !
Next step: perspective (or the face you don't recognize with that big nose in the middle :-) )... Or why it is independent of the focal length but in direct relationship with the distance between the subject and the film plane (or captor, or CCD)...

The fact, as shown in Colman's drawings, that different focal lengths (i.e. the usual lens naming) gives you different viewing angles is often confused with the "perspective" effect (the too big nose).
Most people think that with a wide angle you have a "bad" portrait, while with a mid-tele that's not a problem...

As in the drawings above, we tend to "fill" the frame for a portrait (just an example), so with a tele we are at some distance of the subject, while with a "wide-angle" we would be much nearer, thus accentuating the perspective effect.

It works with buildings too, when people want to get the whole church "in the frame" they often favor a great wide-angle lens increasing the weird feeling that parallels spires are meeting in some not too far points !

When you don't have the backing space for a "frame filling" shot (often the case in old cities) it is often easier (i didn't say better) to find a distant viewpoint (the hill outside the village ) and to use a big tele lens...

Or to use your ordinary lens (35m or 50mm) and frame part of the church in a way that conveys the feeling you had when seeing it (the church). :-)


"What can I do, What can I write, Against the fall of Night". A.E. Housman

by margouillat (hemidactylus(dot)frenatus(at)wanadoo(dot)fr) on Fri Mar 7th, 2008 at 07:50:04 AM EST
[ Parent ]
margouillat:
Or to use your ordinary lens (35m or 50mm) and frame part of the church in a way that conveys the feeling you had when seeing it (the church). :-)

As in gioele 's Prague picture below :-)

"What can I do, What can I write, Against the fall of Night". A.E. Housman

by margouillat (hemidactylus(dot)frenatus(at)wanadoo(dot)fr) on Fri Mar 7th, 2008 at 07:53:24 AM EST
[ Parent ]
Scanners are on the desk beside me and Vuescan makes using them convenient ...

Isn't that two separate issues? The face distortion is due to the way it's spread over the frame (compared to how we expect to see it - you can get the same effect by eye if you pay attention to what you're actually seeing), while the meeting spires is more to do with the sensor plane not being vertical - you point it up at the church and that causes distortion.

That's why view cameras can correct for it: you can set the back parallel to the subject and use the front movement to get the framing you want:

x

From Ansel Adam's The Camera.

by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 08:04:24 AM EST
[ Parent ]
You are right about the different problem of non vertical sensor plane :-) (though it's also perspective, but not the one I wanted to mention, two vanishing points are quite enough just now)!

The face distortion is about distance and as you say you can see it if you get near the subject's nostrils :-)

But for a given distance, a tele shot and a wide angle shot will generate the same perspective deformation if you superpose the two pictures (blowing one up or shrinking the other)...

"What can I do, What can I write, Against the fall of Night". A.E. Housman

by margouillat (hemidactylus(dot)frenatus(at)wanadoo(dot)fr) on Fri Mar 7th, 2008 at 08:23:25 AM EST
[ Parent ]
ah, Scheimpflug. Was busy with that a few weeks ago when I had to photograph a muesli box with 4 different perspectives.

I just came back from a sudden trip from Finland; have I missed much?

You have a normal feeling for a moment, then it passes. --More--

by tzt (tztmail at gmail dot com) on Fri Mar 7th, 2008 at 01:56:08 PM EST
[ Parent ]
perspective (or the face you don't recognize with that big nose in the middle :-)

The folks I know who do portraits on a regular basis swear that 100mm to 135mm (35 mm cameras) lenses are the best for such work--just to avoid the problem you mention.  

These lenses also mean that you can get detailed shots without getting too close to the subject.

"Remember the I35W bridge--who needs terrorists when there are Republicans"

by techno (reply@elegant-technology.com) on Fri Mar 7th, 2008 at 11:03:13 AM EST
[ Parent ]
That's the conventional wisdom, certainly.
by Colman (colman at eurotrib.com) on Fri Mar 7th, 2008 at 11:04:13 AM EST
[ Parent ]
It's the CW because it works.  My dad had a 100mm just for portraits.  Man! was that a sweet lens.

"Remember the I35W bridge--who needs terrorists when there are Republicans"
by techno (reply@elegant-technology.com) on Fri Mar 7th, 2008 at 12:56:55 PM EST
[ Parent ]
It depends what you mean by "portrait": if you mean it in the sense of a head-and-shoulders (more or less) picture of a person then yes, a focal length of 75mm to 135mm in 35mm equivalent is considered the most flattering - though some fashion (and "glamour"??) photographers will use much longer lenses than that. I like the shorter end of that - 85mm, which is keeping with more modern convention, I believe. Though I have a nice little 100mm 2,8 which works well too.

For portraits - in the sense of a depiction of a person - that include the environment you can use much wider lenses without making the person look too scary. It's all a matter of how much of the frame they're filling.

by Colman (colman at eurotrib.com) on Sat Mar 8th, 2008 at 04:38:41 PM EST
[ Parent ]
I go out to a meeting and come back to a doubled number of comments!  You hit on a winner.

This is helpful, thanks.  I will have to read over everything again when I am not supposed to be working!

Ad astra per aspera

by In Wales (inwales aaat eurotrib.com) on Fri Mar 7th, 2008 at 10:57:45 AM EST
[ Parent ]
I've been working on this topic since I got the f/1.8 50mm this past week (I didn't think to post any photos though, I have a portrait shot probably worth submitting).

One thing I found in an article - and verified myself experimentally - is that this particular lens reaches a max sharpness at f/2.5. Below that it is noticeably less sharp. The spendier f/1.4 50mm is at max sharpness throughout the aperture range.

I'm really appreciating the VR on my zoom lens after working with the new one. It's really tough to get decent low light shots even at f/1.8 that don't exhibit a fair bit of camera shake.

you are the media you consume.

by MillMan (millguy at gmail) on Fri Mar 7th, 2008 at 01:57:51 PM EST
[ Parent ]
You still can't hand old it below 1/40. Mind you, I've never noticed any softness in either of my 50mm 1.8 lenses* - don't get too caught up on lens tests!

(We have both the AF-D one and a much older manual version.)

by Colman (colman at eurotrib.com) on Sun Mar 9th, 2008 at 11:29:12 AM EST
[ Parent ]
Having less of the picture in focus is actually an advantage. Look at my picture of a bottle on a mountain background below; it's out of focus on purpose. You can't do that with a point and shoot, and my FZ-30 can barely do it.
Artistically, it serves the purpose of focussing the attention on something, and emphasizing depth, frontground vs background, object vs context, etc.
To obtain this effect you need maximum iris operture. In this picture I had to put on a grey filter and 1/1200 exposure, as well as sitting quite close to the bottle while zooming up a bit.
The opposite of this is a camera obscura, ie a pinhole camera, whereby light goes through a tiny puncture, instead of an actual lens system. Everything that gets (somewhat slowly) captured on the sensor is basically in focus. That's about what you get with a point-and-shoot in good lighting condition; just about everything should be focused.
Typically, the more expensive a camera, the larger the sensor and operture, and therefore the more you get this effect.

A 'centrist' is someone who's neither on the left, nor on the left.
by nicta (nico@altiva․fr) on Sun Mar 9th, 2008 at 09:04:17 AM EST
[ Parent ]
Having less of the picture in focus is actually an advantage. Look at my picture of a bottle on a mountain background below; it's out of focus on purpose.

It can be an advantage, depending on what you're trying to achieve - if you don't want the background it's a good thing. Otherwise it's a bad thing.
by Colman (colman at eurotrib.com) on Sun Mar 9th, 2008 at 10:43:05 AM EST
[ Parent ]
Yes but high end cameras can do both (just close the iris down) while cheap cameras can only do one.

A 'centrist' is someone who's neither on the left, nor on the left.
by nicta (nico@altiva․fr) on Sun Mar 9th, 2008 at 10:59:12 AM EST
[ Parent ]
Only if the lens in long enough though - good luck getting any noticeable circle-of-confusion out of a 20mm lens on 35m. It's not just about aperture and focal length either: sensor size makes a big difference as well. My GR-D, which has quite a small sensor and a 28mm wide angle lens, has massive depth-of-field even at f2.8. With the 21mm adaptor you hardly need to focus it, except for macros, while with the 40mm you can get a bit of isolation if the background is far enough away from a reasonably close subject.
by Colman (colman at eurotrib.com) on Sun Mar 9th, 2008 at 11:11:36 AM EST
[ Parent ]

Display:
Login
. Make a new account
. Reset password
Occasional Series