Showing results for 
Show  only  | Search instead for 
Did you mean: 

Aperture Help


Hello everyone.


I'm new to the dslr world and I have Canon 5d mark ii with a EF 24-105mm 1:4 L IS USM macro ultrasonic lens. On Av I can adjust the aperture from 4 to 22 but it does nothing to blur the background of the subject. When I adjust the apertrue number on the camera I do not see the lens open or close. I have no error codes. And on automatic it takes great photos but I wanted to play with the manual settings and get to know how to use them. Any ideas? Thank you!



The aperture is wide open until you press the shutter regardless of selected F stop so that AF can work properly.  Changing the aperture setting won't change the view through the viewfinder unless you press the depth of field preview button at which point you will see what is in focus at your chosen F stop and if looking through the front of the lens you would also see the aperture blades move when the DoF preview button is pushed.


The standard view you get will always be the minimum depth of field the lens can produce at wide open aperture and pressing the DoF button will let you see the near and far limit focus that will actually be recorded.


With a 100MM lens with a maximum aperture of F4 you will need to be fairly close to a subject for good background blur.  Google depth of field calculator and it will provide a nice presentation of the depth of field at various lens lengths, F stops, and subject distance.  I like the one from site called points in focus.



EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video


I used my favorite one and calculated:

for F/4 (which is not a very small F number)

and 50 mm focal length

and 3m subject distance

the range in focus is 2.6 to 3.6 m, or about 1 m


You would need the background to be much farther away to get good blur.


If you really want to experiment with this, I suggest you get the 50mm, F/1.8 lens with that lens:

at f/1.8 and a 3m subject distance:

the focus range is 2.8 to 3.2m, or less than half of the f/4 case.


Good advice above.  You have at least two learning curves to climb.  


One, you need to learn basic photography.  I suggest that you do web searches for articles about “ exposure triangle “ and “ depth of field “.  The camera will record detailed camera, lens, and exposure settings in the image file every time you take a shot.  This information is called metadata, which is data that describes data.  In the photography world it is called EXIF data.  You need to learn how to read this data, so that you can understand the good, the bad, and the ugly shots you will take as you learn about photography.


Number Two is the Big One.  You need to learn about the camera, and how DSLRs work.  You also need to learn about lenses.  But first, you need an in-depth understanding of how the camera works.  This means learning how to adjust the camera controls and settings to get the type of exposure described by the exposure triangle.  


Secondly, you need to learn how the camera interacts and controls lenses.  The camera has a shooting mode dial on the top surface.  The best mode to learn about the camera’s functions and controls is “P” mode.  The best mode to learn about your lens is probably [A] mode, but you will need to know how to read the EXIF data in your image files.

While [A] mode does not allow you to control settings, which is where “P” mode comes in, you can observe the exposure settings that the camera uses under different shooting conditions.  One of the best things you can do is buy a tripod, and set it up in front of a comfortable chair, along with a copy of the Instruction Manual on a tablet PC, and experiment.


Once you begin to learn how to take the photographs that you want, you will discover that you will discover that you will get better results shooting as RAW, not JPEG files, and “developing” the RAW digital negatives into printable, viewable JPEG files.

"The right mouse button is your friend."


"I'm new to the dslr world and I have Canon 5d mark ii with a EF 24-105mm 1:4 L IS USM macro ultrasonic lens"

"Any ideas?"


You really need to just go out and use the camera. Shoot the same scene at various settings.  Check your results and remember what you like.  You can read all the books and web stuff but actually doing it will provide you with much greater knowledge. Web experts rarely know how photography really works. Go out and shoot.


If you really want nice bokeh and OOF BG's, f4 is not the best aperture. It will work.  A lens in the f2 or f1.8 and better and f1.2 will give you stunning shots.


if you don't have the manual for you very good 5D Mk II get one and read it.  It is a book you need to read......thoroughly.

EOS 1DX and 1D Mk IV and several lenses!


Thanks for the input everyone!. I can see now I didn't have a issue with the lens it was that the lowest f stop is 4 and I need to get a lens that goes to a 2.8 or 2 and of course I need to get out there and practice with the camera!

One of the many advantages of digital is that you can take a lot of images at virtually zero cost other than time so learning through experience is far less expensive than during the film days. 


The DoF preview button really becomes your friend when you are trying to do the opposite of blurring the background; taking a "deep" group photo with everyone in focus.  Keep in mind that the area of acceptable focus is shallower to the front of the perfect focus point than the back so if you are centering focus on a scene of some depth you don't want to focus in the exact center of the set of subjects/objects you want in focus.  The DoF calculator combined with practice will make this simple for you to set up.


With your current lens to blur the background you need to be as close as you can to the subject while still keeping it fully in frame AND making sure the background is far enough away to be sufficiently blurred.  For individual subjects a long and fast lens provides more opportunities but distance from the object and distance to subjects behind still matters. 


The following two shots were both taken with a 300mm F2.8 wide open.  The first was the last soccer game of the season for our younger players and I am surprised that they weren't "smurf blue" given the horrible cold and high wind conditions.  Background blurs nicely because they nearly filled the full frame from a reasonably close shot.  The second image was from the night before at the last high school varsity football game of the season.  In this case the catch was made at the far side of the field so at that distance there is quite a bit of background detail.  It was also shot at 40,000 ISO because of poor lighting conditions and at a lower ISO with less "grain" even more background detail would be evident.


300 2.8 1.JPG


300 2.8 2.JPG



EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video

Great shot of the FB player Rodger.  Smiley Happy

EOS 1DX and 1D Mk IV and several lenses!

Thanks Ernie!  



EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video

"Here's a link to an example I found using to search.  I told it to look for images taken with the 24-105 ..."


This is OK but why not go do it yourself? Why look at other folks doing it instead of you doing it?  Why not get the hands on experience yourself?  You will learn more when you do it yourself.  Rodger made a good point, digital is cheap. Shoot all you want.


"I need to get out there and practice with the camera!"


Yeah, you do.  You really do.


In the olden days we used to think of f4 as the breaking point or middle point.  Anything above f4 was considered a slow lens and anything below was considered a fast lens.  A more open aperture, so you are right in thinking f2.8 and f2 and below will be easier or more practical lets say for OOF BG's.  This is not to say you can't do it with any lens, you just have to know how.  You will learn that outside shooting pictures.

EOS 1DX and 1D Mk IV and several lenses!
01/18/2023: New firmware version 1.1.1 is available for EOS R6 Mark II
01/09/2023: Help ensure your autofocus is properly aligned with a Canon Precision Alignment
01/03/2023: Welcome to CES 2023!
12/08/2022: New firmware version is available for EOS C70
12/07/2022: New firmware version 1.7.0 is available for EOS R5
12/07/2022: New firmware version 1.7.0 is available for EOS R6
11/22/2022: New firmware available for EOS R3, EOS R7 and EOS R10
11/16/2022: We're thrilled to be ranked among the Best Employers for Veterans in 2022 by Forbes.
08/31/2022: New firmware version 1.1.1 is available for RF 70-200mm L IS USM
08/09/2022: New firmware version 1.2.0 is available for CR-N 300
08/09/2022: New firmware version 1.2.0 is available for CR-N 500
07/14/2022: New firmware version 1.0.1 is available for CR-X300
06/10/2022: Service Notice:UPDATE: Canon Inkjet Printer continuous reboot loop or powering down
06/07/2022: New firmware version 1.3.2 is available for PowerShot G7 X Mark III
05/31/2022: Did someone SAY Badges?
05/26/2022: New firmware version is available for EOS-C500 Mark II
05/26/2022: New firmware version is available for EOS-C300 Mark III
05/10/2022: Keep your Canon gear in optimal condition with a Canon Maintenance Service
05/05/2022: We are excited to announce that we have refreshed the ranking scale within the community!
04/26/2022: New firmware version is available for EOS R5 C
03/23/2022: New firmware version is available for EOS-C70
02/09/2022: Share Your Photos is back!
02/07/2022: New firmware version 1.6.1 is available for EOS-1DX Mark III
01/13/2022: Community Update. We will be retiring the legacy profile avatars on 01/20/2022. Click this link to read more.