f1.8 on full frame = f1.8 on crop frame?


furyhawk

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Mar 8, 2010
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#1
as the qns above, doesn't crop sensor capture less amount of light?
 

wildcat

Senior Member
Sep 8, 2004
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Bedok
#2
I think what it means is that 50mm f1.8, when cropped to 75mm will not be 75mm f1.8
 

futsal123

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Jul 15, 2008
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#3
as the qns above, doesn't crop sensor capture less amount of light?
Aperture will still be f1.8. Due to crop sensor factor, focal length will multiply.
Light going through the lense might be lesser (depending on scenario) by 0.3 stop etc.
 

song

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Feb 23, 2002
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#4
does that mean the bokeh effect of F1.8 in full frame is the same as cropped frame? I think the bokeh effect is larger in cropped frame because the effective bokeh that you are looking at is at a larger focal length due to the 1.6X factor.
 

futsal123

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Jul 15, 2008
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#6
does that mean the bokeh effect of F1.8 in full frame is the same as cropped frame? I think the bokeh effect is larger in cropped frame because the effective bokeh that you are looking at is at a larger focal length due to the 1.6X factor.
Bokeh effect as in?
Bokeh should be dependent on the lense no of blades.
 

aspenx

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Aug 10, 2008
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#8
Aperture will still be f1.8. Due to crop sensor factor, focal length will multiply.
Light going through the lense might be lesser (depending on scenario) by 0.3 stop etc.
Actual focal length DOES NOT multiply.

Assuming you have 2 cameras, one full frame and one with a cropped sensor that are both 10MP, have 2 exact same lenses on both cameras, taking the same photo from the exact same spot and settings will give you the same DOF.

However, if you step forward with your fullframe setup such that the subject takes up the same number of pixels in the pictures as it would on the cropped sensor at the previous position, you will get a more shallow DOF then.

This topic has been discussed to death several times already. Try doing a search next time...
 

aspenx

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Aug 10, 2008
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#9
Bokeh effect as in?
Bokeh should be dependent on the lense no of blades.
So you mean a 9-bladed lens by default gives better bokeh than a 7-bladed one? :nono:

I believe the topic of bokeh is in the newbie's corner.
 

Gengh

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May 6, 2007
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#10
A cropped sensor is exactly as the term implies - it's just a crop of the full image. The qualities of the image formed by the lens is not affected by the sensor. The amount of light (energy) per unit area does not change, and the amount and the quality of the bokeh does not change either. Basically, if you take a pic with a FF camera, and crop it by 1.5x in PS, that is what the cropped sensor camera is going to get at exactly the same settings.

The amount of light captured by each individual pixel will be different, just because a FF sensor has larger pixels than a cropped sensor. But this difference is not something that we need to be concerned about since the camera makers have already calibrated the sensors to the ISO standard.
 

futsal123

New Member
Jul 15, 2008
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#11
Think I just embarassed myself in lack of knowledge. Thanks for correcting me.
Long way to learn.
 

Shen siung

Senior Member
May 21, 2008
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#12
as the qns above, doesn't crop sensor capture less amount of light?
It doesn't capture less amount of light. But the field of view will be different. And, the bokeh / back ground blurr will be different.
 

Dec 14, 2008
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#13
for the same framing the background and the background blur will be different too. on full frame there's a wider angle contribution, and you get to approach your subject closer than on a cropped
 

giantcanopy

Senior Member
Feb 11, 2007
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#14
as the qns above, doesn't crop sensor capture less amount of light?
the cropped sensor will capture the same amount of light as the central cropped portion of an equivalent FF sensor with the same aperture setting. aperture and the focal length do not change. A 50mm f1.8 on an aps-c and an ff will not be changed on MF or LF..
 

Numnumball

Senior Member
Mar 6, 2009
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#15
Only the fov changes, the same amount of light will still falls on the sensor though on aps-c ones, on the center portion of the fx lens are used. :)
 

Numnumball

Senior Member
Mar 6, 2009
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#16
does that mean the bokeh effect of F1.8 in full frame is the same as cropped frame? I think the bokeh effect is larger in cropped frame because the effective bokeh that you are looking at is at a larger focal length due to the 1.6X factor.
1.5 lar brother..

1.6 is the other camp (canon) :)
 

May 5, 2009
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#17
Actual focal length DOES NOT multiply.

Assuming you have 2 cameras, one full frame and one with a cropped sensor that are both 10MP, have 2 exact same lenses on both cameras, taking the same photo from the exact same spot and settings will give you the same DOF.
erm, but when i use the online DOF calculator, at same focal length, aperture and subject distance, DX camera will have less DOF than FX camera.

anyone can explain? :think::think:
 

chalib

Senior Member
Oct 4, 2007
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#18
erm, but when i use the online DOF calculator, at same focal length, aperture and subject distance, DX camera will have less DOF than FX camera.

anyone can explain? :think::think:
You can't compare FF and crop at the same subject distance as the FOV is already different.

If you compare using subject distance on the SAME FOV, you will get equal DOF
 

Oct 4, 2008
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#19
erm, but when i use the online DOF calculator, at same focal length, aperture and subject distance, DX camera will have less DOF than FX camera.

anyone can explain? :think::think:
As others mention above, if picture taken at the same spot, there is no differet. However, to achieve the same framing, u need to stand closer to the subject with the full frame, which lead to shallower DOF.
 

May 5, 2009
480
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#20
You can't compare FF and crop at the same subject distance as the FOV is already different.

If you compare using subject distance on the SAME FOV, you will get equal DOF
As others mention above, if picture taken at the same spot, there is no differet. However, to achieve the same framing, u need to stand closer to the subject with the full frame, which lead to shallower DOF.
thanks for the reply, yes i understand about the FOV.

but my question here is, as what bro aspenx said in his previous reply, taking photo from exactly same spot (same subject distance?), with exactly same settings, same lens (same focal length?), one on FX and on on DX, will give you same DOF. of cause the FOV from both camera will be different in this case.

but the data from DOF calculator says the DOF will be different.:dunno::dunno:

Assuming you have 2 cameras, one full frame and one with a cropped sensor that are both 10MP, have 2 exact same lenses on both cameras, taking the same photo from the exact same spot and settings will give you the same DOF.
 

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