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Tony Background Blur Full Frame Vs. Compact Dslr


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#1 geohv66

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Posted 07 February 2016 - 03:15 PM

In one of your videos you said that a full frame DSLR can get better background blur than a compact DSLR. You never said why, using the same lens, ISO, f stop and megapixels one should get the same background blur. What allows a full frame DSLR to get better background blur?

#2 john whittaker

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Posted 08 February 2016 - 11:26 AM

most compact dslr are crop factor sensors.

when using a crop factor sensor with a lens designed for a full frame camera , the effect is the picture looks like you have stepped closer to your subject.

or zoomed in more.

Any time you zoom in more or move closer to your subject your back ground will be more out of focus or more boka... back ground blur, than a full frame sensor size. this is when all settings and distance are the same.

 

so if you take 2 pictures of the same subject , from the same distance the full frame camera will always have less boka or blur as you call it, than a crop factor sensor.

 

hope this helps.



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#3 geohv66

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Posted 10 February 2016 - 02:01 PM

Thank you, that makes total sense, that is the same effect as a compact DSLR has to a old 35 mm when comparing say a 50 mm lens to 85 mm lens being about equal

#4 captain_slow

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Posted 10 February 2016 - 02:12 PM

Um no that's not at all correct

 

With the same camera and lens, the more you zoom in, the more blurred the background gets, the closer you focus, the more the background blurs. 

 

this is why if you have a kit lens and you wan to do a portrait, your best bet is to zoom all the way in and get as close as possible to your subject. 

 

the problem with crop sensors is that you cannot get as close as a full frame sensor and still get the framing you want, so you are usually focusing further away, and you get less background blur. 

 

the other thing is that the larger your sensor/film, the shallower your depth of field will be. to calculate equivalent depth of field, you can multiply your aperture by your crop factor. 

 

so Canon has 1.6x crop, 1.6 x F2.8 = F4.48, therefore a f2.8 lens on a crop canon sensor will yield similar background blur as a full frame sensor with a F4.5 lens, given that focal length and focus distance is the same. 

 

in any case, to get the best background blur use the longest focal length available to you at the widest aperture available, and get as close as possible to your subject. 


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