Very newbie question on lens focal length and perspective - 未名空间MITBBS历史存档

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Very newbie question on lens focal length and perspective

Very newbie question on lens focal length and perspective# PhotoGear - 摄影器材

o*s2013-09-23 07:09

1 楼

I am a bit slow, please bear with me,
If I have a 12mm lens on a 1.6X crop body, and another photographer is using
a 19.2mm lens on a full frame and we stand on the same spot, essentially we
are taking the exact same view, right?
If the other photographer is using a 12mm lens on a full frame, I need to
step further back to get the same view as he does, but i will never get the
same view? Since the distance of me to the subject is different than the
distance of him to the subject?
dumb and confused.

a*l2013-09-23 07:09

2 楼

第一种情况，透视相同，景深不同。第二种情况透视不同了，所以可以认为得到的画面
不同。

J*o2013-09-23 07:09

3 楼

终结此贴了

【在 a********l 的大作中提到】

: 第一种情况，透视相同，景深不同。第二种情况透视不同了，所以可以认为得到的画面
: 不同。

o*s2013-09-23 07:09

4 楼

lol thanks apolitical. I am also terrible with Chinese. Have to trouble you
to explain in English. Please please. and assume the person know absolutely
nothing about 景深 or 透视.

J*o2013-09-23 07:09

5 楼

Google perspective and depth-of-field
http://en.wikipedia.org/wiki/Perspective_(graphical)
http://en.wikipedia.org/wiki/Depth_of_field

o*s2013-09-23 07:09

6 楼

Thanks Judsonzhao,
dof = 景深 and perspective = 透视, right?
The first situation, the frame will be the same, but different dof, 2nd
situation, frame is different since the distance of lens to subject changed,
correct?
Now i just have to figure out how/why the dof differ.

a*l2013-09-23 07:09

7 楼

这个对透视的解释非常直观，我都让人看这个
http://www.dpreview.com/glossary/optical/perspective

【在 J********o 的大作中提到】

: Google perspective and depth-of-field
: http://en.wikipedia.org/wiki/Perspective_(graphical)
: http://en.wikipedia.org/wiki/Depth_of_field

a*l2013-09-23 07:09

8 楼

焦距越长，景深越小，背景虚化的更厉害。

changed,

【在 o**s 的大作中提到】

: Thanks Judsonzhao,
: dof = 景深 and perspective = 透视, right?
: The first situation, the frame will be the same, but different dof, 2nd
: situation, frame is different since the distance of lens to subject changed,
: correct?
: Now i just have to figure out how/why the dof differ.

o*s2013-09-23 07:09

9 楼

make sense? I feel like i understood something in college but still get C on
an exam.
so the full frame person will have shallow dof?

【在 a********l 的大作中提到】

: 焦距越长，景深越小，背景虚化的更厉害。
:
: changed,

o*s2013-09-23 07:09

10 楼

Good one. Thank you! I swear I have studied this before but give it all back
again.

【在 a********l 的大作中提到】

: 这个对透视的解释非常直观，我都让人看这个
: http://www.dpreview.com/glossary/optical/perspective

G*m2013-09-23 07:09

11 楼

您老是abc?

you
absolutely

【在 o**s 的大作中提到】

: lol thanks apolitical. I am also terrible with Chinese. Have to trouble you
: to explain in English. Please please. and assume the person know absolutely
: nothing about 景深 or 透视.

o*s2013-09-23 07:09

12 楼

no, but I 老 am at a point where both English and Chinese are broken.

【在 G*****m 的大作中提到】

: 您老是abc?
:
: you
: absolutely

o*s2013-09-23 07:09

13 楼

do you have another nice tutorial on the first case / dof?
Thanks!

【在 a********l 的大作中提到】

: 焦距越长，景深越小，背景虚化的更厉害。
:
: changed,

a*l2013-09-23 07:09

14 楼

是的。

on

【在 o**s 的大作中提到】

: make sense? I feel like i understood something in college but still get C on
: an exam.
: so the full frame person will have shallow dof?

a*l2013-09-23 07:09

15 楼

你可以试验一下，不用两台相机，一台相机就行（残幅只是全幅中间抠出来一部分），
变焦镜头，同样光圈情况下拍照，焦距越大景深越小。

【在 o**s 的大作中提到】

: do you have another nice tutorial on the first case / dof?
: Thanks!

o*s2013-09-23 07:09

16 楼

Okay, dof depends on focal length, focal distance, and aperture, if FD and A
are the same, then longer FL= shallower dof? I can't understand the
physics, can i just memorize the fact as a property? I know (from experience
) that tele-lens tend to have shallow dof.
staying over time at work trying to understand dof...

a*l2013-09-23 07:09

17 楼

是的。拍多了就知道了，不用记忆。

A
experience

【在 o**s 的大作中提到】

: Okay, dof depends on focal length, focal distance, and aperture, if FD and A
: are the same, then longer FL= shallower dof? I can't understand the
: physics, can i just memorize the fact as a property? I know (from experience
: ) that tele-lens tend to have shallow dof.
: staying over time at work trying to understand dof...

o*s2013-09-23 07:09

18 楼

Thank you!
I keep forgetting that the only thing that changes perspective is distance
to subject, that I need to move around. Lens focal length only changes how I
frame the subject.
http://photography-on-the.net/forum/showthread.php?t=672913

【在 a********l 的大作中提到】

: 是的。拍多了就知道了，不用记忆。
:
: A
: experience

J*o2013-09-23 07:09

19 楼

correct
no matter it's a 6mm or 600mm lens, if the subject distance is fixed, you
will get the same perspective, but different frames.

I

【在 o**s 的大作中提到】

: Thank you!
: I keep forgetting that the only thing that changes perspective is distance
: to subject, that I need to move around. Lens focal length only changes how I
: frame the subject.
: http://photography-on-the.net/forum/showthread.php?t=672913

n*s2013-09-23 07:09

20 楼

一？阿婆会讲中文耶。。。奇迹。。。

o*s2013-09-23 07:09

21 楼

man this stuff is hard - perspective and composition.

b*t2013-09-23 07:09

22 楼

看看gaussian beam

【在 o**s 的大作中提到】

: do you have another nice tutorial on the first case / dof?
: Thanks!

o*s2013-09-23 07:09

23 楼

Thanks.

【在 b*******t 的大作中提到】

: 看看gaussian beam

a*l2013-09-23 07:09

24 楼

我中英文一样烂，你没发觉吗？

【在 n****s 的大作中提到】

: 一？阿婆会讲中文耶。。。奇迹。。。

a*l2013-09-23 07:09

25 楼

一图胜千言，你的疑问全部解开了吧？

【在 o**s 的大作中提到】

: Thanks.

w*72013-09-23 07:09

26 楼

try online dof Calculator

【在 o**s 的大作中提到】

: do you have another nice tutorial on the first case / dof?
: Thanks!

G*m2013-09-23 07:09

27 楼

中文是您老母语?

【在 o**s 的大作中提到】

: no, but I 老 am at a point where both English and Chinese are broken.

o*s2013-09-23 07:09

28 楼

I thanked her. Did I say anything else?
I gave up.

【在 a********l 的大作中提到】

: 一图胜千言，你的疑问全部解开了吧？