Totally blurred background with sharp subject in macro?

Started Jan 17, 2012 | Discussions
Romaric New Member • Posts: 10
Totally blurred background with sharp subject in macro?

Hi,

I have been playing with my Nikon 60mm macro lens trying to achieve the same type of pictures than in the websites or magazines. There is one thing I never succeed to do: get a perfectly sharp subject (flower) and a completely blurred background. How can they get a full flower perfectly sharp (not just a small portion), while achieving perfectly blurred background where no shapes or lines are visible?

Playing with the aperture I can get one or the other but never both. Typically, my background are blurred but still recognisable while I would like to get only patches of colours.

Is it a limitation coming from my short (cheap) focal length? Do they blur the background in post processing? Or am I doing something wrong?

Thanks for your help,
Romaric

orionmystery
orionmystery Senior Member • Posts: 2,052
Re: Totally blurred background with sharp subject in macro?

You need a longer lens to render the background completely out of focus and blur.

This write up might help you understand better:
http://orionmystery.blogspot.com/2011/01/sigma-150-vs-sigma-180.html

(unknown member) Forum Pro • Posts: 19,115
Re: Totally blurred background with sharp subject in macro?

Do you mean like this?

http://kvincentphotography.ca/macro/h154035fc#h154035fc
http://kvincentphotography.ca/endlesssummer/h24919e97#h19779148
http://kvincentphotography.ca/endlesssummer/h24919e97#h2c01bc32

Please note, all three images were taken with the 105 2.8 VR lens and shot at f/22.

The simple trick is (IF you only have a relatively short lens to work with)...is to position the subject at least 25-30 feet in front the background. Plus, shoot as close as possible to the subject.

Also, they may stack the images (of the subject only) this creating a great DOF...but leaving the background blurred.

This image doesn't have a blurred background but it is stacked just as an example.
http://kvincentphotography.ca/stackedimages/h7247ccf#h7247ccf

Or, they may be using a 300mm lens with an extension tube...which will isolate the subject very well and also create a nice soft backgound bokeh.

Hope this helps...

KEV

"It is a small gesture, but one that can be very effective - especially in a large crowd. So fart, and if you must, fart often. But always fart without apology. Fart for freedom, fart for liberty, and fart proudly" (Benjamin Franklin 'The Dream' 1751)

http://kvincentphotography.ca/stackedimages
http://kvincentphotography.ca/designerflorals
http://kvincentphotography.ca/macro

trulandphoto
trulandphoto Contributing Member • Posts: 880
Re: Totally blurred background with sharp subject in macro?

The distance from the subject to the background is what makes the difference. The greater the distance, the greater the difference in focus between the two.
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OP Romaric New Member • Posts: 10
Re: Totally blurred background with sharp subject in macro?

Thanks everybody. Indeed the background need to be as far as possible but even then I can not achieve the type ofpictures you show me in your links. So it is coming from my short focal. The problem of short distance to subject is well known in all the forums but it seems the problem of lower background blur is not as well known.

I will try to play with stack of images until I can afford a long focal macro lens.
Cheers,
Romaric

trulandphoto
trulandphoto Contributing Member • Posts: 880
Re: Totally blurred background with sharp subject in macro?

Romaric wrote:

Thanks everybody. Indeed the background need to be as far as possible but even then I can not achieve the type ofpictures you show me in your links. So it is coming from my short focal. The problem of short distance to subject is well known in all the forums but it seems the problem of lower background blur is not as well known. [...]

Actually, focal length plays little part in creating what you call "background blur." A rule of macro photography is that if your subject is the same size in the view finder and you are using the same aperture, the depth of field is the same regardless of what focal length lens you are using.

So, regardless of whether you are two inches away with a wide angle lens or ten feet away with a super telephoto, if the insect - or whatever, is the same image size, and you are using the same aperture, the depth of field will be the same.

Granted, with a longer lens you will have a narrower view of the background, and that, in and of itself, can isolate the subject from the background, but "blur" is not a part of it.

Here's a quote from John Shaw's book "Closeups in Nature - The Photographer's Guide to Techniques in the Field", page 50: "All lenses that are focused at the same image size (the subject is the same size in the frame) and the same f-stop have the same depth of field." This is a great book, btw, and while written in the film age, the techniques remain valid.
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_sem_ Veteran Member • Posts: 5,033
Re: Totally blurred background with sharp subject in macro?

trulandphoto wrote:

Actually, focal length plays little part in creating what you call "background blur." A rule of macro photography is that if your subject is the same size in the view finder and you are using the same aperture, the depth of field is the same regardless of what focal length lens you are using.

This is not the whole truth. It is true regarding the DoF calculations that affect the depth of the critically sharp region. But the FL is awfully important regarding the look of the out-of-focus area such as the background. This is why shorter lenses may make the impression of more depth, as the background is relatively less blurred. For example, put a 20mm on the 5.6mm K-1 ring and stop it down, and you can make a close-up with almost sharp mountains in the background.

Dave Martin Senior Member • Posts: 2,160
TC for blurred background with sharp subject in macro...

Use a teleconverter with your macro lens. For the same image in the viewfinder a 2x teleconverter will render background details twice as large which will be perceived as 1/2 as sharp. This is because the teleconverter effectively increases the lens' focal length.

Or, get a macro lens with a longer focal length.

These photos show the effect of changing lens focal length on the rendering of the crackerbox in the background.

trulandphoto
trulandphoto Contributing Member • Posts: 880
Re: Totally blurred background with sharp subject in macro?

sem wrote:

trulandphoto wrote:

Actually, focal length plays little part in creating what you call "background blur." A rule of macro photography is that if your subject is the same size in the view finder and you are using the same aperture, the depth of field is the same regardless of what focal length lens you are using.

This is not the whole truth. It is true regarding the DoF calculations that affect the depth of the critically sharp region. But the FL is awfully important regarding the look of the out-of-focus area such as the background. This is why shorter lenses may make the impression of more depth, as the background is relatively less blurred. For example, put a 20mm on the 5.6mm K-1 ring and stop it down, and you can make a close-up with almost sharp mountains in the background.

That makes some sense. That the degree of "out of focus" is affected by focal length. I'll experiment once it's warm enough to be outside for more than 10 seconds.

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_sem_ Veteran Member • Posts: 5,033
Re: Totally blurred background with sharp subject in macro?

trulandphoto wrote:

That makes some sense. That the degree of "out of focus" is affected by focal length. I'll experiment once it's warm enough to be outside for more than 10 seconds.

You can trust me on this one

For practice you don't have to go out; the computer screen shot at a steep angle is perfect for short/long macro comparisons.

Notice the absolute blur does not depend on the FL, I mean for example at a certain magnification say 1:1 and F-stop a bright dot 10cm behind the focus point gets blurred to 1cm blur disc regardless of the FL. But for the relative blur, the size of the background area captured at this distance matters. With a long telephoto macro, the size is hardly larger than the frame size 35x24mm, so the blur disc is almost half its height. With a short macro, the size of the background area may be many times larger, so the blur disc looks many times smaller.

http://forums.dpreview.com/forums/readflat.asp?forum=1030&message=39021378
http://forums.dpreview.com/forums/readflat.asp?forum=1030&message=38923775

cjed Senior Member • Posts: 2,039
Re: Totally blurred background with sharp subject in macro?

I think you need to have the background much further behind the subject. If the background is reasonably close a change in focal length or aperture will not in itself be enough to throw the background completely out of focus. You may have to change the viewpoint to make sure any visible background is well behind the subject.

Here's a little test I did to show the effect of aperture and focal length on DOF at 1:1 magnification : http://www.pbase.com/cjed/macrodof

In that gallery, the background was fairly close to the subject (but well outside the DOF). In the the following shot, you can see how something in the near background (left-hand side) is still recognizable, while folliage in the far background is not.

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Check out my galleries (lots of macros) at :
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closeupfanatic Senior Member • Posts: 1,184
Photoshop it

Use Photoshop. Select the sharp item with magnetic lasso, invert the selection, then apply blur and soften until it looks the way you want. Much easier than the darkroom methods pros have used for over a century.

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DecibelPhoto Contributing Member • Posts: 791
Re: Totally blurred background with sharp subject in macro?

I really think it only has to do with the RELATIVE distance between your subject and the background. Your subject needs to be as close as possible while still being fully in focus, and your background as far as possible. With a flower, it may need to be within a foot, with your background 20' away.

_sem_ Veteran Member • Posts: 5,033
Re: Totally blurred background with sharp subject in macro?

DecibelPhoto wrote:

I really think it only has to do with the RELATIVE distance between your subject and the background. Your subject needs to be as close as possible while still being fully in focus, and your background as far as possible. With a flower, it may need to be within a foot, with your background 20' away.

Well the relative distance is important, but the FL matters too. In the sample below with the 20/3.5 F/22 on K1 ring, roughly 1:3 closeup, the lens is a couple of cm from the flower, yet the background is far from "totally blurred".

AndreSerfontein Junior Member • Posts: 41
Re: Totally blurred background with sharp subject in macro?

My 2c would be that it depends on the lens you are using. If I shoot with my Tamron 18-270mm Dii VC PZD at full zoom using a +4 diopter, I can blur the background fairly effectively using a smaller aperture.

However, I now shoot macro almost exclusively using a Nikkor N 24mm f2.8 reverse mounted to my Canon 600D. With this lens even at high f-stop, the depth of field is so little that anything further away simply becomes an unrecognizable blur.

Also keep in mind how you light your subject. With dedicated lighting you will have more control over exposing your subject so that the background is much darker.

If you like look at a sample photo I've taken today. The background behind the spider is about 30cm away.

http://www.flickr.com/photos/mikndruk/6774588943/in/photostream

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_sem_ Veteran Member • Posts: 5,033
Re: Totally blurred background with sharp subject in macro?

AndreSerfontein wrote:

However, I now shoot macro almost exclusively using a Nikkor N 24mm f2.8 reverse mounted to my Canon 600D. With this lens even at high f-stop, the depth of field is so little that anything further away simply becomes an unrecognizable blur.

Yes magnification matters - you're using a wideangle lens but that's 5-to-10 times more magnification, so much less DoF, much more absolute blur, so also much more relative blur. Yet your sample still makes much more impression of subject depth than one made with the same magnification with a long lens (on bellows) would.

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