Background blur in photos: I took this photo using an EF50mm f/1.8 Mk1 lens on my EOS 40d. The subject was about 4-5 feet from my position. The background blur was not as I had hoped...

EoS_User Loc: Oshawa, Ontario Canada

I took this photo using an EF50mm f/1.8 Mk1 lens on my EOS 40d. The subject was about 4-5 feet from my position. The background blur was not as I had hoped for. I was using Av mode with the aperture set to 1.8. I changed it to 22 (max for this lens) and as expected got very deep depth of field. To increase background blur do I need longer focal length or shorter focal length?

One of 20 painted hydrants

Nikonian72 Loc: Chico CA

The larger an aperture, the more shallow the DoF. (f/4 is larger than f/22).
The longer the focal length, the more shallow the DoF.

FAQ: Understanding Depth of Field
http://www.uglyhedgehog.com/t-45532-1.html

robert-photos Loc: Chicago

EoS_User wrote:

I took this photo using an EF50mm f/1.8 Mk1 lens on my EOS 40d. The subject was about 4-5 feet from my position. The background blur was not as I had hoped for. I was using Av mode with the aperture set to 1.8. I changed it to 22 (max for this lens) and as expected got very deep depth of field. To increase background blur do I need longer focal length or shorter focal length?

For DOF of various lenses, apertures and distances see:

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

cesarakg Loc: Candelaria - Brazil

AFAIK, these are the things that affect the background blurr (shallow Dep of Field = background blurr):

1. lens focal length - the biggest focal length gives the shallow DOF.

2. the aperture - the biggest aperture gives the shallow DOF.

3. the relationship of the distances: lens - subject - background.

http://www.photomatters.org/aperture-focal-length-distance
http://en.wikipedia.org/wiki/Depth_of_field

And there's that thing, the "bokeh", the effect of background blurr on background light sources.

St3v3M Loc: 35,000 feet

Nikonian72 wrote:

The larger an aperture, the more shallow the DoF. (f/4 is larger than f/22).
The longer the focal length, the more shallow the DoF.

FAQ: Understanding Depth of Field
http://www.uglyhedgehog.com/t-45532-1.html

That was easy

RTR Loc: West Central Alabama

What Nikonian72 said.

Gary Truchelut Loc: Coldspring, TX

the longer the focal length the more bokeh or blurred background. It also makes a difference how far the background is from the subject. If you had used a telephoto lens, say in the 135 to 200mm range your background would have been much more blurred.
Of course you would have been farther from your subject in order to keep it the same size in the shot.

rpavich Loc: West Virginia

Gary Truchelut wrote:

the longer the focal length the more bokeh or blurred background. It also makes a difference how far the background is from the subject. If you had used a telephoto lens, say in the 135 to 200mm range your background would have been much more blurred.

Ok...this is slightly highjacking the thread but...since the OP has his / her answer I'll mention it.

Isn't what Gary said actually IN-correct (that focal length determines (partially at least) DOF and therefore blur of the background?

Isn't the DOF ALWAYS the same no matter what focal length you use (assuming that you frame the subject the same everytime (i.e. subject same amount of frame filling)

Or do I have it wrong?

cesarakg Loc: Candelaria - Brazil

Gary Truchelut wrote:

Isn't the DOF ALWAYS the same no matter what focal length you use (assuming that you frame the subject the same everytime (i.e. subject same amount of frame filling)

I think you are right. If you move the camera to make the subject the same size in the frame, then the DOF will be almost the same, AFAIK.

There's a table comparing different focal length and different distances from the subject, and the resulting DOF, here:
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

It would be better if you try it with a camera, as in this link here:
http://www.photokaboom.com/photography/learn/tips/037b_dof_focal_length.htm

katbandit Loc: new york city

personally i like the way it was shot ...why would you have wanted the background to distract from the main subject of the fire hydrant ..if you wanted to include the entire background then maybe stepping further away from the whole scene and shooting at f22 would have given you more of what you wanted..

docrob Loc: Durango, Colorado

EoS_User wrote:

I took this photo using an EF50mm f/1.8 Mk1 lens on my EOS 40d. The subject was about 4-5 feet from my position. The background blur was not as I had hoped for. I was using Av mode with the aperture set to 1.8. I changed it to 22 (max for this lens) and as expected got very deep depth of field. To increase background blur do I need longer focal length or shorter focal length?

neither - just move closer to the subject

mafadecay Loc: Wales UK

EoS_User wrote:

I took this photo using an EF50mm f/1.8 Mk1 lens on my EOS 40d. The subject was about 4-5 feet from my position. The background blur was not as I had hoped for. I was using Av mode with the aperture set to 1.8. I changed it to 22 (max for this lens) and as expected got very deep depth of field. To increase background blur do I need longer focal length or shorter focal length?

There was not much more you can do with this lens. The closer to the subject you get and the further away the background then you would have got more blur. The long end on a tele would also give more blur.

Can I just add that this lens is notoriously sharp but not at f/1.8 When I used it I did stay away from the f/1.8 realm and used the lens to its best potential and sharpness around f/5.6, f/8, f/11 although this is not the effect you were looking for in this particular image.

I would try and stay away from the mins and max of a lens where ever possible as it will perform better out of this zone.

coco1964 Loc: Winsted Mn

mafadecay wrote:

quote=EoS_User I took this photo using an EF50mm ... (show quote)

Exactly---at 1.8 on a 50mm you're going to have the blurred background. It looks to be daylight out so why were you shooting at 1.8 if you wanted to get the entire photo in focus. These "Nifty Fifty" lens take some getting used to---tack sharp but touchy with the blurring.....

mafadecay Loc: Wales UK

coco1964 wrote:

quote=mafadecay quote=EoS_User I took this photo... (show quote)

No I think the OP intended to get more blur on the background hence the f/1.8 aperture. The OP was suprised at how little blur there ended up being. You are right Coco about having to get used to the nifty fifty.

If it is background blur you seek off your 50mm you could maybe try adding a close up filter (is it a 52mm thread) to it allowing you to achieve focus much closer to the subject. Trouble is you would be too close for the framing you demonstrate here. This would really blur the BG then though. Otherwise you can get an adapter ring that allows you to mount the lens backwards on your body turning it into a better than macro lens. Not technically better but more magnification than 1:1

coco1964 Loc: Winsted Mn

mafadecay wrote:

coco1964 wrote:

quote=mafadecay quote=EoS_User I took this photo... (show quote)

No I think the OP intended to get more blur on the background hence the f/1.8 aperture. The OP was suprised at how little blur there ended up being. You are right Coco about having to get used to the nifty fifty.

If it is background blur you seek off your 50mm you could maybe try adding a close up filter (is it a 52mm thread) to it allowing you to achieve focus much closer to the subject. Trouble is you would be too close for the framing you demonstrate here. This would really blur the BG then though. Otherwise you can get an adapter ring that allows you to mount the lens backwards on your body turning it into a better than macro lens. Not technically better but more magnification than 1:1

quote=coco1964 quote=mafadecay quote=EoS_User I... (show quote)

Sorry I misunderstood, can't hardly believe it, lol...........