Background blur, aperture and focal length

[ruley74]

Ok, so i have a question that has been lingering in my head for a while (it's pretty empty so it bounces for a while )….

It is often discussed to get those awesome OOF backgrounds the big primes are the way to do it, particularly the 600/4. However, a good deal of the time we tend to shoot these tools at say F8 to ensure DOF for detail.

So, is there/would there be a noticeable difference in the backgrounds between a 600/4 and a say 150-600 (pick a brand) if both were shot at F8 and all else equal?

I've seen some comparisons on the interwebs where people show how much better the big primes are in this sense but are we comparing them wide open most of the time...

Thoughts?

I am unbiased as I use both a 200-500 and a 400/2.8 and both of them produce what i want some times and other times not as much as i thought.

 

[Steve]

It depends (I think that's my catch phrase ).

If you're talking strictly about how blurry the background is due to DoF, then no. DoF is the same for any given focal length and F/stop combination. (Although technically DoF doesn't describe the amount of background blur, but rather the area in the image that displays acceptable sharpness).

Now, if you're talking about how that background his rendered, you'll almost certainly see a difference between those optics - heck, between just about any two optics. The "bokeh" can and does vary between lenses and can make a background look better or worse. Generally, it's better with more expensive primes than it is the less expensive zoom lenses.

 

[DougC]

“Generally, it's better with more expensive primes than it is the less expensive zoom lenses.“
This is oh , so true!

 

[ruley74]

It depends (I think that's my catch phrase ).

If you're talking strictly about how blurry the background is due to DoF, then no. DoF is the same for any given focal length and F/stop combination. (Although technically DoF doesn't describe the amount of background blur, but rather the area in the image that displays acceptable sharpness).

Now, if you're talking about how that background his rendered, you'll almost certainly see a difference between those optics - heck, between just about any two optics. The "bokeh" can and does vary between lenses and can make a background look better or worse. Generally, it's better with more expensive primes than it is the less expensive zoom lenses.

Haha, yep, I guess considering the combination of both achieving the required sharpness (DoF) and still rendering a great background (bokeh...hate that word!). So for me it's more about the optical formula than the focal length vs aperture (taking distance to subject & background being the same).

 

[Callie]

All the above is true, the long, costly glass is better as it has been proven and argued over many years and forums.
I like to play devil's advocate, though. In yesteryear, when slides and negatives were what everyone did, this is true and directly in digital photography too. But once you put a raw file through it paces in your PP, the F/large or F/smaller does not matter because you can make the F/smaller look like the F/larger. I do this all the time and really cannot see the difference. I am biased to the lighter lenses F/ smaleer, for mobility and maneuverability while excepting that the Bokeh directly from the longer f/larger lenses are better in camera. I have owned both the 400 F/2.8 and the 600 F/4 and now the 500 PF and my final images between these lenses are on par after PP. So for me the question is, after the "additional" PP work that I put in, or the less PP time for the F/larger lenses, what is the norm then to compare two similar images. We cannot see > 72 to 96 dpi anyway on a screen, and wildfife is not realy portrait studio work printing. Just my subjective view formed over many years of shooting basically only wildlife in our national parks.

 

[GailTori]

Callie, would you be willing to give a quick description of what you are doing in PP to get the bokken you talked about?

 

[Callie]

Callie, would you be willing to give a quick description of what you are doing in PP to get the bokken you talked about?

@GailTori There is not a quick answer, but I will try and give an overall methodology that I use.
Open ACR, Set Optics.
In basics, set Auto. I always use flat or neutral. Play a bit to visually eyeball what I like. You can fade etc in ACR, but I am not there yet.
Open in PS.
The first thing I do is curves using Alt click on auto. Eyeball this again to get what I want.
Depending on the image, I crop to my preferred fee for the image, loosing the cropped pixels.
Now several things may be done, depending on the image - both subject and BG,
You can now select the subject much easier than previously. I place the subject as a layer mask on a new layer and duplicate this layer with the mask.
I apply the mask to the top layer, this gives a layer with subject only and what other objects I deemed belong to the foreground.
Then I return to the layer below, invert the mask and apply it. Now you have a BG layer with a hole in it where the subject was removed, Lasso the empty space and content aware fill.
This BG layer now forms the basis that I work with.
Firstly, I denoise.
Then I duplicate the layer.
Now I use the duplicated, denoised layer, to run Gausian blur or other blurs, still learning the tricks.
Now, here is the thing. You can blur a lot, or less, but the thing to do is to make your subject visible, so that it is visible on the blurred and denoised layer.
Now you apply a mask to this blurred/denoised layer, but you start off selectively with a low opacity. You paint over the layer to reveal what you want to see, say detail at the subject's feet but little detail in the BG up to the top of the frame. There is normally very little but bush, etc behind the image or just blotches of bad colour and intermingled light.
Now, to get rid on any blotches, highlights etc, you create a new layer above the BG layer we talked about, and below your subject layer, and you paint over, using the brush tool and the BG colours for colour picking by pressing the alt key while clicking in the frame on the colour, using the brush tool.
In this way, you can do to the BG what you want. I personally do not like what is referred to as Bokeh as it looks to me like OOF blotches in many instances, but that is subjective and by no means meant to be derogatory on the taste of others. The image I append of a Lilac Breasted Roller in Kruger is typical of what I do. You see it fades the BG from the FG. Now, the lens does not necessarily give me this. This image I must revisit because I did it 2 years ago and I have since learned and practiced more so should get a better transfer.
The black-backed jackal in Kruger is typical of blurring the BG and again, needs rework as there are patches I would take out today.
Hope this help, but it is hours of trying, Then there is Nik filters too, and they also allows you to do very nice things to the BG and subject too.

You can only see EXIF info for this image if you are logged in.

You can only see EXIF info for this image if you are logged in.

 

[GailTori]

Great explanation, Thank you so much.

 

[gbodave]

No-one seems to have mentioned distance from the subject to the background when trying to obtain good background blur and it's a crucial factor. We can't always get our wildlife subjects to present themselves just in the "right" place but in general I find that when the animal/bird is in the open there isn't a problem with background blur. These comments relate to zoom lenses because I don't use a prime lens.

Here's a typical situation for me where background blur comes out well at 600mm which I shoot at almost exclusively. The background would only be about 30 feet behind the subject.

You can only see EXIF info for this image if you are logged in.

With this one the background stretched out behind the subjects about 1/2 mile. 500mm.

You can only see EXIF info for this image if you are logged in.

 

[ruley74]

No-one seems to have mentioned distance from the subject to the background when trying to obtain good background blur and it's a crucial factor. We can't always get our wildlife subjects to present themselves just in the "right" place but in general I find that when the animal/bird is in the open there isn't a problem with background blur. These comments relate to zoom lenses because I don't use a prime lens.

The question I posed was with all things being equal (did mention distance to subject and background in one of my posts), yes it's definitely one of the biggest factors in getting that smoother background as with a uniform background colour.