How to focus but blur the background?


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syous

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#1
Hi all, like to check with you guys how do i focus an object but blur out the background and vice versa? i did a few experiment but didnt seem to get it right leh... thanks for helping wor.. need to learn photgraphy asap have a very important event next week..
 

_espn_

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#3
i) use a large aperture f/1.4~f/2.8

ii) Make the person stand as far away from the background as possible

iii) Zoom to the max your camera can do.
 

#5
should have posted this at Panasonic forum leh.. im also a FZ7 user.. well.. yeah.. like the guy said.. set to aperture priority at f2.8 then try zoom to 8x is enough to get a blur background, to make the background more blur go all the way to 12x.. but u need a shutterspeed higher then 1/400 to get really nice shots.. I've used it at 1/250 and its nice.. i forgot who told me to use 1/400 le.. i forget how to get the speed also.. anyone teach me how to calculate? i forgot leh.. heh heh
 

raptor84

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#7
Cause at 12x zoom its the 35mm equiv of 420mm so you need a shutter speed of at least 1/400 (general rule) to elimnate handshake. With the OIS on (assuming its a 2-3 stop advantage)you can shot at 1/100 of a sec with no issues though...
 

#8
raptor84 said:
Cause at 12x zoom its the 35mm equiv of 420mm so you need a shutter speed of at least 1/400 (general rule) to elimnate handshake. With the OIS on (assuming its a 2-3 stop advantage)you can shot at 1/100 of a sec with no issues though...
oh yeah,, this is how u see it.. haha.. thanks alot.. and yes.. i usually have my OIS on at mode 2.. Thx a bunch
 

syous

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#9
LightStalker said:
should have posted this at Panasonic forum leh.. im also a FZ7 user.. well.. yeah.. like the guy said.. set to aperture priority at f2.8 then try zoom to 8x is enough to get a blur background, to make the background more blur go all the way to 12x.. but u need a shutterspeed higher then 1/400 to get really nice shots.. I've used it at 1/250 and its nice.. i forgot who told me to use 1/400 le.. i forget how to get the speed also.. anyone teach me how to calculate? i forgot leh.. heh heh
Hey thanks man, i dont quite get it higher then 1/400 meaning 1/500, 1/640 etc... or 1/320, 1/250 etc. so sorry I'm a newbie wor.. Forgive my stupidity.. haha:bsmilie: thanks man!
 

#10
syous said:
Hey thanks man, i dont quite get it higher then 1/400 meaning 1/500, 1/640 etc... or 1/320, 1/250 etc. so sorry I'm a newbie wor.. Forgive my stupidity.. haha:bsmilie: thanks man!
wa.. see u type this very similar to my signature leh.. hahaha.. i also newbie.. so far already had more then 3k clicks on my FZ7.. hahaha.. only had it for 1 month !! and yeah, higher then 1/400 i mean 1/500 and so on.. but the most you really need to go at 12x zoom is 1/400.. which is at about 432mm.. i usually go to 1/500 or 1/1000 on bright sunny days when i wanna freeze something..
 

Apr 12, 2005
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#11
The actual focal length for the FZ7 at 12x optical zoom is only 72mm. So shooting at 1/100 should be ok even without OIS.

Getting a blur background has got to do with the Depth of field which depends on the actual focal length used, distance to the subject, aperture size and the sensor size (Circle of confusion). Read up on depth of field and use the DOF calculator below, you will get an idea :

http://photoinf.com/Tools/Don_Fleming/Depth_Of_Filed_Calculator.html

To have the background blur, it means the background must be outside the focus range (focus range is the near and far limit within which objects will be in focus) as determined by the DOF. Usually, it means using a shallow depth of field (i.e. larger aperture, longer focal length and nearer distance to subject).

If you're interested in the actual calculation of DOF, see here (notice how the DOF will vary with greater/lower values of the paramenters and see how a shallower/deeper DOF can be achieved by varying the focal length, aperture and distance to subject) :

http://www.dofmaster.com/equations.html
 

syous

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#12
LightStalker said:
wa.. see u type this very similar to my signature leh.. hahaha.. i also newbie.. so far already had more then 3k clicks on my FZ7.. hahaha.. only had it for 1 month !! and yeah, higher then 1/400 i mean 1/500 and so on.. but the most you really need to go at 12x zoom is 1/400.. which is at about 432mm.. i usually go to 1/500 or 1/1000 on bright sunny days when i wanna freeze something..
Wah, you make me look so bad. i also bought this camera for 1 month plus but u seem so pro. i took only 600+ photos... haiz. Hey will you be going for the newbie outing to MacRitchie Reservoir 13/08/2006 (Sunday)?
 

Zaknafein

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#13
Clockunder said:
The actual focal length for the FZ7 at 12x optical zoom is only 72mm. So shooting at 1/100 should be ok even without OIS.
.....
hmmm, its this true? can someone verify this pls?
i always thought its the that the general rule of 1/focal length refers to 35mm equivalent?
 

Apr 12, 2005
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#14
Zaknafein said:
hmmm, its this true? can someone verify this pls?
i always thought its the that the general rule of 1/focal length refers to 35mm equivalent?
There have been some discussions before and opinions differ.

I've been shooting at 1/60 for my Nikon Coolpix 5700 at 8x optical zoom (actual 71mm which is 280mm on the 35mm equivalent format) without any much handshake blur problem.

An image formed using 71mm (280mm on 35mm equivalent) on the Nikon 5700 is about the same size as one formed using 71mm (about 420mm on 35mm equivalent) on the FZ7. The difference in 35mm equivalent is due solely to the difference in image(CCD) sensor size. The Nikon 5700 has a larger sensor and therefore the subject appears smaller in the frame than the same image in the frame taken by the FZ7 and therefore the subject looks as if it's taken at only 280mm on the 35mm equivalent format compared to 420mm on a 35mm equivalent format by the FZ7 even though the actual subject size in the image formed is the same for both pictures taken at the same actual focal length (71mm in this example).

Indirectly, it also means that both images are susceptible to the same handshake blur risk if they're taken at the same actual focal length. The 35mm equivalent focal length is just a number telling us the focal length that would be used to have the subject(s) appear this size in the frame if the film/CCD sensor is the full frame 35mm format.

The picture below was taken at 71mm (280mm equivalent on the 35mm format on my Nikon 5700) at 1/60 shutter speed and there is no VR (Vibration Reduction for Nikon, equivalent to OIS for panasonic or IS for Canon) and it's near the threshold of getting handshake blur. If the 35mm equivalent focal length is erroneously used as a guide, then it would demand shooting at least 1/280 already (check the EXIF info in the picture) :


 

_espn_

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#15
Clockunder said:
There have been some discussions before and opinions differ.

I've been shooting at 1/60 for my Nikon Coolpix 5700 at 8x optical zoom (actual 71mm which is 280mm on the 35mm equivalent format) without any much handshake blur problem.

An image formed using 71mm (280mm on 35mm equivalent) on the Nikon 5700 is about the same size as one formed using 71mm (about 420mm on 35mm equivalent) on the FZ7. The difference in 35mm equivalent is due solely to the difference in image(CCD) sensor size. The Nikon 5700 has a larger sensor and therefore the subject appears smaller in the frame than the same image in the frame taken by the FZ7 and therefore the subject looks as if it's taken at only 280mm on the 35mm equivalent format compared to 420mm on a 35mm equivalent format by the FZ7 even though the actual subject size in the image formed is the same for both pictures taken at the same actual focal length (71mm in this example).

Indirectly, it also means that both images are susceptible to the same handshake blur risk if they're taken at the same actual focal length. The 35mm equivalent focal length is just a number telling us the focal length that would be used to have the subject(s) appear this size in the frame if the film/CCD sensor is the full frame 35mm format.

The picture below was taken at 71mm (280mm equivalent on the 35mm format on my Nikon 5700) at 1/60 shutter speed and there is no VR (Vibration Reduction for Nikon, equivalent to OIS for panasonic or IS for Canon) and it's near the threshold of getting handshake blur. If the 35mm equivalent focal length is erroneously used as a guide, then it would demand shooting at least 1/280 already (check the EXIF info in the picture) :


Actually it's blur liao.
 

Apr 12, 2005
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#16
_espn_ said:
Actually it's blur liao.
I do not disagree that it's not sharp and may even be said to be blur.

That's why I said it's near the threshold level of 1/71. In fact, it's below the guideline.

I was just trying to show that if the actual requirement is 1/280, the a picture taken at 1/60 would have lots of handshake blur liao as I was aiming and shooting without making any conscious effort to steady my shots at that time.

To reinforce my point that the guideline should be based on actual focal length rather than the 35mm equivalent, here are some handheld taken pictures (with the 35mm equivalent focal length in brackets) many of which I've posted in this forum before. They may not be very sharp (partly due to the wide-opened aperture at long focal length), they provide evidence to support my argument about using actual focal length as a guide for handheld shots :

71.2mm (280mm) @1/60


56.7mm (223mm) @1/60



71.2mm (280mm) @1/74


71.2mm (280mm) @1/125
 

Zaknafein

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#17
hmmm, sounds logical. thx for talking sense into my head...
now i need to break everything up and figure it out in my head just to be sure i get what u mean.
thanks for explaination!
 

ortega

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#18
to get minimum DOF

1. maximum focal lenght (the longer the better)
2. minimum subject to camera distance (the closer the better)
3. maximum subject to background distance (the further the better)
4. biggest aperture (the bigger the better)

so if you max out the above 4 points you will get the best that your camera can do.
i hope it helps
 

Zaknafein

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#19
does that means there is also an advantage in smaller sensor size compared to bigger sensor size in this sense? excluding other factors like ISO, picture quality.

for a PnS shooting at 300mm, one would need only about 1/100 shutter speed to get a relatively sharp shot. but for DSLR, if 1 is using a 188mm focal length with 1.6x crop factor, bringing it to shooting at ~300mm, would need about 1/200 shutter speed to get a relatively sharp shot?
 

Zaknafein

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#20
ortega said:
to get minimum DOF

1. maximum focal lenght (the longer the better)
2. minimum subject to camera distance (the closer the better)
3. maximum subject to background distance (the further the better)
4. biggest aperture (the bigger the better)

so if you max out the above 4 points you will get the best that your camera can do.
i hope it helps
diagram 1: shortest focal length, closest focus distance to subject(but further than diag. 1)

camera...Xm...Subject................................Ym.....................................Backgnd


diagram 2: Longest focal length, closest focus distance to subject

camera................>Xm............Subject.......................Ym................................Backgnd


given same distance from subject to background, which would have shallower DOF?
or does it depends on focal length used, + all other factors etc etc.....
 

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