Is there a difference between walking two steps forwards and just zoom in?


dapao

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Nov 6, 2010
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#1
I am using zoom lens 99% of the time. Is there a difference of IQ( or whatever you can think of) if I take a photo of an stand-still object eg 1) using 105mm focal length and 2) I walk eg two steps forward using eg 80mm(same lens). (Assume I acheive the composition, able to reach the object and Ignore lightings/ISO and DOF and nothing tricky about the still object)
 

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Jul 2, 2010
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#2
zoom lenses tend to have different types of distortion which increase/decrease according to their focal length
 

Timolol

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Sep 24, 2009
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#3
I am using zoom lens 99% of the time. Is there a difference of IQ( or whatever you can think of) if I take a photo of an stand-still object eg 1) using 105mm focal length and 2) I walk eg two steps forward using eg 80mm(same lens). (Assume I acheive the composition, able to reach the object and Ignore lightings/ISO and DOF and nothing tricky about the still object)
Whatever I can think of: http://en.wikipedia.org/wiki/Perspective_distortion_(photography)
 

Jul 2, 2010
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#5
sorry i have to give my two cents here
perspective is more associated with composition than IQ itself
ts mentioned about IQ at different focal length
sample from the digital picture review about canon 18-200mm:
Continuing on the ever-important image quality topic ... At 18mm, CA (Chromatic Aberration) is strong mid-frame and in the corners. CA improves as the focal length is increased until basically gone at 50mm. By 135mm, CA once again begins to show mid-frame and in the corners and continues to be present through 200mm.

Watch the strong barrel distortion in the middle portion of the frame at 18mm. You will want to keep straight lines away from the borders at this focal length; otherwise, you will see a large bump out of the center with lines straightening again near the corners. To see this, look at the green trim on the corner of the building in the example below.


By 24mm, lines are nearly straight again, but pincushion distortion sets in by 28mm and gets relatively strong by 50mm through 200m. Another way to gauge the amount of distortion present at various focal lengths is to watch the top image in the ISO 12233 sample crop tool change size as different focal lengths are selected. Also, compare the 18-200 images to the nearly-distortion-free Canon EF 200mm f/2.8 L II Lens samples for the same camera.

Flare is well-controlled overall, but shows up stronger at the longer end of the focal length range (where the lens hood is less effective). Here is a Canon-Mount Super Zoom Lens Flare Comparison that shows the EF-S 18-200 to be best-in-class in this regard. Color and contrast seem fine.

Vignetting is visible in the corners at wide open apertures. It is moderately strong at the long end of the focal length range and at 18mm. Being an "EF-S" lens, the 18-200 IS does not have the larger image circle size that a full-frame compatible "EF" lens has and therefore shows more vignetting on the EF-S compatible bodies it mounts on (all have a 1.6x FOVCF).

The Canon EF-S 18-200mm f/3.5-5.6 IS Lens is relatively sharp in the center even wide open. Stopping down to f/5.6 brings nice sharpness to the center of the image through 50mm. Use f/8 from 80mm through 200mm for best center sharpness. Corners are soft wide open and need f/8 for good sharpness over most of the focal length range. Corners are decent at f/5.6 at 18mm and prefer f/11 at 135mm. Sharpness out of this lens definitely exceeded my expectations.
so yes to answer the question, different focal length of a zoom lens will give different IQ

ok i realised TS said (whatever you can think of) so yeah perspective would change too
 

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Radiant

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Oct 19, 2009
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#6
Hi TS, since you already have the zoom, you can easily do the simple test yourself. I think you can answer your own question quite easily.

Important thing is to know your equipment and use it effectively. my 2 cents worth.
 

sin77

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Nov 28, 2004
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#7
the perspective got difference one.
call it field of view or view of field??

Also can reduce handshake if u are not using a fast lens that can fixed at largest aperture at all zoom
 

agws1970

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#8
I am using zoom lens 99% of the time. Is there a difference of IQ( or whatever you can think of) if I take a photo of an stand-still object eg 1) using 105mm focal length and 2) I walk eg two steps forward using eg 80mm(same lens). (Assume I acheive the composition, able to reach the object and Ignore lightings/ISO and DOF and nothing tricky about the still object)
All things remaining the same. DOF and perspective changes come to mind.
 

alantkh

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Jun 16, 2009
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#12
simple answer.

your frame has two objects.
Object A at 8 steps away.
Object B at 100 steps away.

If you take two steps forward,
Object A gets bigger by 25%.
Object B gets bigger by 2%.

If you zoom in with a focal length 25% longer,
Object A gets bigger by 25%.
Object B gets bigger by 25%.

SIMPLE? if still cannot understand....
 

pinholecam

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Jul 23, 2007
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#13
I am using zoom lens 99% of the time. Is there a difference of IQ( or whatever you can think of) if I take a photo of an stand-still object eg 1) using 105mm focal length and 2) I walk eg two steps forward using eg 80mm(same lens). (Assume I acheive the composition, able to reach the object and Ignore lightings/ISO and DOF and nothing tricky about the still object)
Assuming you are on a zoom like a Nikkor 18-105 f3.5-5.6)
A few things :
1. Slight DOF difference (80mm@f4.5@2.5m : DOF 0.17m; 105mm@f5.6@3m : DOF 0.18m)
2. Shutter speed needed for less chance of camera shake (1/80 vs 1/100)
3. Likely Bokeh difference (f4.5 vs f5.6; larger oof light sources vs smaller)
4. IQ depending on how the lens is optimized
5. FOV
 

night86mare

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Aug 25, 2006
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#14
it's simple, just think of having a chair in front of you blocking say, the view of the sea.

now, you walk in front 2 steps, the view of the sea is less blocked.

if you walk in front of the chair, there is no issue at all.

simple answer, no?
 

Jul 2, 2010
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#15
it's simple, just think of having a chair in front of you blocking say, the view of the sea.

now, you walk in front 2 steps, the view of the sea is less blocked.

if you walk in front of the chair, there is no issue at all.

simple answer, no?
i like your answer :D
 

torak

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Sep 4, 2009
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#16
in a hazy (or even just abit of haze) atmospheric environment, walking closer to subject, rather than standing further and zooming in, will give a much better detail and IQ.
 

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Oct 22, 2009
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#17
a lot of difference in perspective, you just try it at 18mm and 105mm, with maybe your living room table as the subject. the pictures will speak more then what we can describe to you here.

but short answer is yes, there is a difference!
 

torak

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Sep 4, 2009
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#18
a lot of difference in perspective, you just try it at 18mm and 105mm, with maybe your living room table as the subject. the pictures will speak more then what we can describe to you here.

but short answer is yes, there is a difference!
i think what TS meant is that with the same FOV, will it make a difference to walk forward (to the desired FOV), or to just zoom the lens in, to the same FOV...

Therefore "perspective" will be the same, unless there's something blocking the view, as per night86mare's example.
 

GRbenji

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May 24, 2010
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#20
i think what TS meant is that with the same FOV, will it make a difference to walk forward (to the desired FOV), or to just zoom the lens in, to the same FOV...

Therefore "perspective" will be the same, unless there's something blocking the view, as per night86mare's example.
When one zoom the lens in, it increases the focal length. Increase in focal length reduces FOV. So how can FOV not change?

What TS meant was to have the subject filling the frame at the same size by either moving forward or zooming in. Moving forward uses a wided FOV hence give the perspective that the background is further away. Zooming in used a narrower FOV hence pushing the subject and background closer.

Look at the pics below. Notice the lamp post size is maintained but background is being pull closer as focal length increases.

@ 17mm


@ 35mm


@ 50mm


@100mm
 

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