Max Aperture on Crop Sensor


Status
Not open for further replies.

KY1977

New Member
Jan 3, 2008
947
0
0
#1
Pardon me for my potential silly question. Does a FF lens appear to be give a crop camera a larger aperture?
 

HHenrYY

New Member
Mar 18, 2009
235
0
0
Singapore
#2
maximum aperature depends on the lens.

FF lens on dx body
or
dx lens on FF body
maximum aperature is the same,
it all depends on lens ..
 

drakon09

New Member
Aug 12, 2005
3,877
0
0
#3
The FF lens will project an image circle too large for a cropped-sensor camera (hence the use of the term "crop" in the first place, as the smaller sensor uses the centre crop of the image circle).

Aperture is a function of the lens and is independent of camera.
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,517
31
48
Pasir Ris
#4
Pardon me for my potential silly question. Does a FF lens appear to be give a crop camera a larger aperture?
You might want to read a bit about Aperture. You'll notice that the whole article doesn't even mention the camera body.
 

3in1c

New Member
Oct 23, 2008
609
1
0
40
East
#5
Would you like to share why you think that way? Could be interesting...
 

Richter

New Member
Sep 11, 2005
147
0
0
#7
I am also not sure if I understand the question by TS correctly.

The aperture size is the same.

However, the DOF of FX will be shallower than DX using lens of same focal length and subject of the same size. The reason is because for DX to have the subject of the same size as the FX using lens of same focal length, you have to move back. The increase of focus distance will increase the DOF.

You can use this website to calculate the DOF that you will have. http://www.nikonians.org/html/resources/guides/dof/hyperfocal2.html

Not sure if I am right. Can the experts please correct if I have misunderstooding on the Apertures.
 

LukaviZ

New Member
Feb 3, 2009
367
0
0
Singapore, East Sider
#8
last heard, the bokeh of an F4 on FF is about the same as F2.8 on crop. Not sure how true it is, but I believe it. Anyone concurs on this?
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,517
31
48
Pasir Ris
#9
last heard, the bokeh of an F4 on FF is about the same as F2.8 on crop. Not sure how true it is, but I believe it. Anyone concurs on this?
How can you seriously believe something if you are not sure whether it is true? Photography is not a religion.
Apart from that, a little bit of reading about bokeh and aperture (plenty of links available here in forum) will show you the factors that contribute to bokeh. Here is a recent thread discussing Out of Focus and Bokeh. The sensor size is never mentioned...
 

Last edited:

Rashkae

Senior Member
Nov 28, 2005
19,105
12
0
#10
Not sure how true it is, but I believe it. Anyone concurs on this?
I definitely do not concur on this. Also, you should not believe things you do not know to be true. If you do, I would like to interest you in a deal, I have $60M hidden away from a dead warlord in Somalia, I just need some assistance from you to transfer it, my dear trusted friend...
 

Pupster

New Member
Feb 22, 2009
28
0
0
#11
In terms of exposure, the aperture is only dependent on the lens. This is because exposure is a factor of light intensity, it doesn't matter if you crop out the center part of the image circle, the intensity is still the same.

Bokeh is a little more difficult to understand. It is related to the physical size of the aperture, lens-to-subject and lens-to-background distance, if my memory serves me correctly. Anyway, the image circle cast by your lens is fixed. Take for example a 135mm f/2 lens on a fullframe sensor, you get a certain image. On an APS-C sensor, you are just taking the center part of the image circle, equivalent to cropping the image from the fullframe sensor.
 

swhyge

New Member
Apr 5, 2003
524
0
0
Jurong
Visit site
#12
.......... Also, you should not believe things you do not know to be true. ...........
100% agreed!. Unfortunately, some do, and a few even come out with own theories and experience to support it. Quite sad..
 

Last edited:

ZerocoolAstra

Senior Member
Mar 13, 2008
9,522
0
0
rainy Singapore
#13
Richter said:
I am also not sure if I understand the question by TS correctly.

The aperture size is the same.

However, the DOF of FX will be shallower than DX using lens of same focal length and subject of the same size. The reason is because for DX to have the subject of the same size as the FX using lens of same focal length, you have to move back. The increase of focus distance will increase the DOF.

You can use this website to calculate the DOF that you will have. http://www.nikonians.org/html/resources/guides/dof/hyperfocal2.html

Not sure if I am right. Can the experts please correct if I have misunderstooding on the Apertures.
Yes you are right. SPOT ON! :)
The depth of field is a function of:
a) lens' focal length
b) aperture
c) focus distance
Up to this point there's no mention about the camera body itself.

The reason that 50mm f/1.8 can give a thinner depth of field on FF vs cropped is that with the FF camera, you can go closer (reduction in focusing distance) to get the same FOV as on the cropped camera. And vice versa, you have to step back with the cropped camera, causing an increase in focus distance, and consequently greater depth of field.

ps. I don't know what is "misunderstooding" though ;)
 

Last edited:

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#14
size of aperture is still the same, value is still the same
however, the depth of field will change, larger the film format, narrower the depth of field.

so on when on digital sensor, FX sensor will have narrower depth of field compare to a DX sensor using the SAME lens.
 

swhyge

New Member
Apr 5, 2003
524
0
0
Jurong
Visit site
#15
size of aperture is still the same, value is still the same
however, the depth of field will change, larger the film format, narrower the depth of field.

so on when on digital sensor, FX sensor will have narrower depth of field compare to a DX sensor using the SAME lens.
You missed out an important parameter for this to be true.... cf Richter's post.
 

Del_CtrlnoAlt

Senior Member
Feb 15, 2003
16,268
0
0
Outside the Dry Box.
Visit site
#16
size of aperture is still the same, value is still the same
however, the depth of field will change, larger the film format, narrower the depth of field.

so on when on digital sensor, FX sensor will have narrower depth of field compare to a DX sensor using the SAME lens.
simplest way to explain...

if you have a full frame camera, shoot an image with say 50mm f1.4 with a subject in the middle. (pic A)

then using that same image, draw a square box in the middle then cut it out. (pic B)

Pic A is the full frame with more 'bokeh' than Pic B as Pic B is your Cropped Sensor.

Image is the same, as aperture and shutter speed, etc is the same, standing at the same distance, hence same bokeh.

Too tight for Pic B, take a step back.

Take the image again with full frame. (pic C)

then same crop on pic C (pic D)

Pic C will have much more room than Pic D, but after cropping althou subject look the same. Bokeh of Pic B & D will not be the same. Distance change affect bokeh.
 

ZerocoolAstra

Senior Member
Mar 13, 2008
9,522
0
0
rainy Singapore
#17
simplest way to explain...

if you have a full frame camera, shoot an image with say 50mm f1.4 with a subject in the middle. (pic A)

then using that same image, draw a square box in the middle then cut it out. (pic B)

Pic A is the full frame with more 'bokeh' than Pic B as Pic B is your Cropped Sensor.


Image is the same, as aperture and shutter speed, etc is the same, standing at the same distance, hence same bokeh.

Too tight for Pic B, take a step back.

Take the image again with full frame. (pic C)

then same crop on pic C (pic D)

Pic C will have much more room than Pic D, but after cropping althou subject look the same. Bokeh of Pic B & D will not be the same. Distance change affect bokeh.
Sorry I don't quite understand what you mean by the sentence I highlighted in bold.
Pic A and Pic B both have the same depth of field, as Pic B is just a crop of Pic A.
What is "more bokeh"??
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#18
thank you for highlighting missing out something in my last post, I just assuming that everyone will compare the same size of the subject relativity to the image frame.
 

Status
Not open for further replies.
Top Bottom