Depth of Field Help

[TheBigE]

I am looking for some advice on how to control DOF. To give a bit of background, lets look at the attached picture below, my goal was to really isolate Olaf, but I really was not able to do so with my equipment - D5300 and 18-140mm f3.5-f5.6. I had a vision in my mind and could not seem to get it to work on the camera.



I played with 140 mm and 18mm Focal Lengths (and their corresponding widest apertures), along with moving closer and further to Olaf. In the end, nothing seemed to produce the image I was looking for - Olaf in sharp focus with a very out of focus background.

I guess I would like to know a starting point in terms of minimizing depth of field. For example, I have found the Sunny 16 rule to be quite helpful when outside and walking around. I always try to dial back my camera to this point as I walk around. It is just a good starting point for my settings and then I can dial in as needed, does anything like that exist for DOF? I also know that I could use a DOF calculator, but I do not always have time to pull out my phone and calculate (in this case only had a few minutes before someone else took over Olaf). So what can be my starting point e.g. - Max Zoom and Aperture and minimum Distance.

Given the variables I can control I believe the following are in order of impact on DOF - Aperture, Focal Length or Distance to Subject. So in my case, perhaps my equipment was not optimum and my 35mm f1.8 Lens lesson should have been the answer (I did not have this with me at the time) Any thoughts on how I could approach this situation and in the future would be very helpful. Thanks for the help.

[NorthernFocus]

It sounds like you are already acquainted with DOF calculator. It may be very instructive for you to look at your settings for each shot that you took, recall the distance you were shooting, and try to reconcile that after the fact with what the DOF calculator is telling you. You can gain an understanding much quicker by using a much simpler scene. Set something on a post or table with nothing in the background for at least a few meters. Then with you zoom lens go out and shoot it from a fixed distance with various zoom and aperture settings and compare.

It is not difficult once it clicks with you. Good luck.

[NorthernFocus]

By the way, I looked at your galleries. You have a creative eye.

[Polar01]

Erik it may help us if we had some idea of your vision of Olaf, to say it has to do with DOF really does not give much info.

Cheers: Allan

[Mike Buckley]

I've got a few ideas for you to consider, Erik.

You need to determine, perhaps first, whether you want all or only part of Olaf to be in focus. If the former, you are restricted in this scene because the width of Olaf is large enough that your aperture that keeps all of him in focus will at best throw items near Olaf out of focus only slightly. The change might be so slight that you would have to review the image at a very large size to perceive the difference in sharpness.

If you decide that you want all of Olaf in focus, you could more easily throw the background out of focus by controlling what is and is not in the background. As an example, you could take a profile view of Olaf that includes only or at least mostly the vegetation in the background. The vegetation is so far away from Olaf that you could keep all of Olaf in focus and throw the vegetation considerably out of focus.

As I mentioned, you could also decide to keep only part of Olaf in focus. That decision would of course make it a lot easier to throw all of the background items, even the items that are close to Olaf, out of focus because even parts of Olaf would be out of focus.

My long-winded point is that compositional changes in your image will render the background in or out of focus even though the distance between the subject and camera, the focal length and aperture remain unchanged among the various compositions.

[TheBigE]

It sounds like you are already acquainted with DOF calculator. It may be very instructive for you to look at your settings for each shot that you took, recall the distance you were shooting, and try to reconcile that after the fact with what the DOF calculator is telling you. You can gain an understanding much quicker by using a much simpler scene. Set something on a post or table with nothing in the background for at least a few meters. Then with you zoom lens go out and shoot it from a fixed distance with various zoom and aperture settings and compare.

It is not difficult once it clicks with you. Good luck.

By the way, I looked at your galleries. You have a creative eye.

Dan, thank you for the compliment!!! I have played around with the DOF calculator and cannot seem to draw a conclusion on where I need to be, and I think as you suggested more practical exercises are the answer. It is funny, sometimes I hit it and sometime I do not. I really think my Lens (in this case) was at its limit of it capabilities for DOF. I think I could have meet my vision with my 35mm f1.8.

Erik it may help us if we had some idea of your vision of Olaf, to say it has to do with DOF really does not give much info.

Cheers: Allan

Allan - Sure not a problem. Basically I was looking to pull out Olaf from the photo. I saw all the "action" in the background and thought it would look good out of focus with Olaf in strong focus. Similar to a Portrait photo in some cases. I am not sure how to explain it, other than I really wanted a blurry background. If you look close on the photo the background is not perfectly clear but still viewable. Perhaps something similar to the photo below is what I was looking for...

[Polar01]

Erik that is what I thought you wanted but just wanted to make sure. To get that nice soft background is also largely dependent on the distance from said subject to the background. The shorter the distance the harder it is to get that soft background you want. Two possible things that may work, if the DOF is say 3ft (that is 1ft in front and 2ft behind) without refocusing move back until Olaf is at the back of the 3ft DOF, now what will change is your FOV (field of view). Another is in post, if working in Photoshop using smart objects, make a selection of Olaf and place on new layer with mask, then go back into the smart object and use negative clarity to blur the back ground.

Cheers: Allan

[chauncey]

Allan's technique is what I would use...it does, however, require knowledge of Photoshop.

[DanK]

Erik,

You may need to consider background blur as well as DOF. See the section on background blur here: http://toothwalker.org/optics/dof.html. If you take two lenses, one shorter and one longer, and change your position so that Olaf is the same size in the frame, the DOF will be the same, but the background blur will be greater with the longer lens.

Dan

[Mike Buckley]

If you take two lenses, one shorter and one longer, and change your position so that Olaf is the same size in the frame, the DOF will be the same, but the background blur will be greater with the longer lens.

Thanks for sharing that link. I had never thought about the details of apparent blur as opposed to actual blur.

[AB26]

Erik,

I am very stupid when it comes to doing all sorts of calculations while shooting.

In my experience: the closer you are to the subject and the wider open the aperture, the shallower the DOF will be. The opposite is also true: the further you move away from your subject and the narrower the aperture the more DOF you will get.

Try shooting Olaf at 18mm F3.5 moving closer and further away and see if there is any difference.
A good starting point - wide open at shortest FL and close to the subject.

I can see a princess in the BG but I think she has melted!

[Manfred M]

Try shooting Olaf at 18mm F3.5 moving closer and further away and see if there is any difference.

Umm, no. At 18mm focal length, even at f/3.5 on a crop frame at a normal shooting distance, just about everything will be in focus. I would do the opposite and start at the longest focal length at f/5.6; that will more likely achieve what Erik is trying to do.

That being said, DoF is dependent on the aperture and amount of magnification, so regardless of the focal length, if the framing is identical, the DoF will be the same regardless of the focal length. With a longer focal length the amount of magnification will tend to be higher, so DoF tends to be shallower.

With a crop sensor one loses about 1 stop of DoF versus FF due to crop factor, so fast glass, shot wide open is even more critical on a crop camera.

[Polar01]

Andre sorry to say that you are incorrect, if you had experience shooting in the UWA range you would know that there is no way, and that most everything would be in focus. I find this pretty well true with anything under 27mm, at 28mm and up I find that I need to watch my DOF, this is because I usually shoot landscapes and cityscapes, personally liking a large DOF to get everything in focus.

[William W]

I am looking for some advice on how to control DOF. To give a bit of background, lets look at the attached picture below, my goal was to really isolate Olaf, but I really was not able to do so with my equipment - D5300 and 18-140mm f3.5-f5.6. I had a vision in my mind and could not seem to get it to work on the camera.

IF it is ONLY Depth of Field that is your question, then it is simple Mathematics which will provide the answer.

FACTS:

> Your lens is a varying maximum aperture zoom lens.

> (for most shots made at a usual Portrait Shooting Distance) Provided the Aperture and Camera Format do not change – for any one particular FRAMING, the DoF will remain CONSTANT no matter what Focal Length is used.


Therefore

You will attain the SHALLOWEST Depth of Field possible, for ANY framing that you choose, by using any Focal Length that allows you to use F/3.5.

The TIGHTER the FRAMING the shallower will be the DoF.

My guess is, with your lens, that you will be using FL = 18mm to about 22/24mm.

WW

[William W]

Dan mentioned Background Blur.

I think that there are three subsections of ”Background Blur”.

> 1. The Background Blur which quantifiable by those technical elements that will also constitute Depth of Field (I understand that is what Dan refers to, when he posed the example of using two different Focal Lengths at the same FRAMING –the DoF will be the same but the Background Blur will be different.

> 2. The Background Blur intrinsic to the lens design that which makes it different to other lens’s Background Blur (for two examples: the shape of and the number of the Aperture Blades in a lens)

> 3. The Texture of and Lighting on the Background will affect the Blur Image.

I do NOT think of the Quantifiable Background Blur (as described in point one) as the equivalent of BOKEH.

I think of BOKEH as the combination of the THREE Background Blurs I sectioned.

If you want a “calculator” for Background Blur (the first one that I mentioned) then seek out ‘Bob Atkins’ Background Blur Calculator’ – I have found it handy, not so much in the field but for studying and anticipating the BB with different lens’s Focal Lengths and Framings, to allow me to include in my choice of Focal Length, Background Blur dynamics, especially when using Zoom Lenses.

Incidentally, Bob's calculator also makes a measurement of Foreground Blur, which is part of HEKOB, but most who rave lyrical about the wonders of BOKEH, never give even a slight mention to HEKOB, which is very biased thinking, in my opinion.

WW

[AB26]

Manfred and Allan,

I am not so sure how incorrect I might be.

For any given focal length lens: the closer the focal plane gets to the subject the more the BG will be OOF, at any given aperture.
The wider open the aperture the shallower the depth of focus will be.
If for any reason you need to increase the depth of focus you increase the subject to focal plane distance and /or narrow down the aperture.

The limiting factor will be minimum focusing distance of any lens.

For instance: Take a Nikkor 10.5mm f2.8 fisheye lens with a minimum focusing distance of only 140mm. Focus on a subject at 140mm at f2.8 and the BG will be more OOF than it will be if you move back 100mm – to 240mm from the subject. Move back even further, holding down the AF-ON button in AF-C and eventually the BG will no longer be OOF even at f2.8.

You will also notice: the subject to focal plane distance at any given aperture will influence the circles of confusion, in other words – the bokeh.

I might be wrong but it works for me.

[Polar01]

Andre look at what Erik is shooting and you are saying, here are the numbers, 11mm focus distance 140mm (.459ft) near limit .44ft far limit .49ft total DOF .05ft. Now really in what world are you shooting in you are less than 6 inches from the item, now if shooting extreme closeup with the wide angle yes, but maybe look at Erik's subject again and see if what you say will work there.

Cheers: Allan

[TheBigE]

Erik that is what I thought you wanted but just wanted to make sure. To get that nice soft background is also largely dependent on the distance from said subject to the background. The shorter the distance the harder it is to get that soft background you want. Two possible things that may work, if the DOF is say 3ft (that is 1ft in front and 2ft behind) without refocusing move back until Olaf is at the back of the 3ft DOF, now what will change is your FOV (field of view). Another is in post, if working in Photoshop using smart objects, make a selection of Olaf and place on new layer with mask, then go back into the smart object and use negative clarity to blur the back ground.

Cheers: Allan

Allan - I think for this case that will probably be my only answer, I have a working level of PS and could probably work to obtain the image in my mind. I would like to get it closer in the future in the camera.

Erik,

You may need to consider background blur as well as DOF. See the section on background blur here: http://toothwalker.org/optics/dof.html. If you take two lenses, one shorter and one longer, and change your position so that Olaf is the same size in the frame, the DOF will be the same, but the background blur will be greater with the longer lens.

Dan

Dan, thanks for the feedback and link to a really good article. I had to read it a couple of times to comprehend, but in short it really brought out the difference between Background Blur and DOF. What I was looking for was background blur in my photo and trying to accomplish this by minimizing DOF.

Umm, no. At 18mm focal length, even at f/3.5 on a crop frame at a normal shooting distance, just about everything will be in focus. I would do the opposite and start at the longest focal length at f/5.6; that will more likely achieve what Erik is trying to do.

That being said, DoF is dependent on the aperture and amount of magnification, so regardless of the focal length, if the framing is identical, the DoF will be the same regardless of the focal length. With a longer focal length the amount of magnification will tend to be higher, so DoF tends to be shallower.

With a crop sensor one loses about 1 stop of DoF versus FF due to crop factor, so fast glass, shot wide open is even more critical on a crop camera.

Manfred - thanks for the clarification. I think reframing with at 140mm on my lens, despite being more closed on the Aperture (f5.6) might have been an option. From the article above, the higher magnification essentially magnifies the areas behind the image that blurred. Perhaps in my image there was not enough behind Olaf that was far out enough to be blurred. I hope that makes sense (seems to make sense in my mind).

Dan mentioned Background Blur.

I think that there are three subsections of ”Background Blur”.

> 1. The Background Blur which quantifiable by those technical elements that will also constitute Depth of Field (I understand that is what Dan refers to, when he posed the example of using two different Focal Lengths at the same FRAMING –the DoF will be the same but the Background Blur will be different.

> 2. The Background Blur intrinsic to the lens design that which makes it different to other lens’s Background Blur (for two examples: the shape of and the number of the Aperture Blades in a lens)

> 3. The Texture of and Lighting on the Background will affect the Blur Image.

I do NOT think of the Quantifiable Background Blur (as described in point one) as the equivalent of BOKEH.

I think of BOKEH as the combination of the THREE Background Blurs I sectioned.

If you want a “calculator” for Background Blur (the first one that I mentioned) then seek out ‘Bob Atkins’ Background Blur Calculator’ – I have found it handy, not so much in the field but for studying and anticipating the BB with different lens’s Focal Lengths and Framings, to allow me to include in my choice of Focal Length, Background Blur dynamics, especially when using Zoom Lenses.

Incidentally, Bob's calculator also makes a measurement of Foreground Blur, which is part of HEKOB, but most who rave lyrical about the wonders of BOKEH, never give even a slight mention to HEKOB, which is very biased thinking, in my opinion.

WW

William - Thanks for the information, and it helps clear up the point of background blur which is what I was really trying to do in the above image. While f3.5 will give me the shallowest DOF, a higher magnification can result in increased background blur. This is assuming you have set up for background using the points you have listed above.

***

Thanks again everyone for the excellent input. I am thinking there is more trial and error in my future to really nail this down and meet the vision that I have in my mind....that or more time with PS.

[jcuknz]

I have skipped through this thread but my solution, which I have not put into practice ever, is to put the background out of focus you focus closer than the subject and utilise the unwanted DoF to maintain apparent sharpness in the subject ... seems logical to me
To date I have done it in editing by making a duplicate layer, putting it out of focus and then erasing it where I want sharpness in the original below ... it is so easy and quick ... why bother doing in-camera



If you want to be fussy you can make several layers at different levels of blur to simulate the progression of softness.

[Shadowman]

I have skipped through this thread but my solution, which I have not put into practice ever, is to put the background out of focus you focus closer than the subject and utilise the unwanted DoF to maintain apparent sharpness in the subject ... seems logical to me
To date I have done it in editing by making a duplicate layer, putting it out of focus and then erasing it where I want sharpness in the original below ... it is so easy and quick ... why bother doing in-camera



If you want to be fussy you can make several layers at different levels of blur to simulate the progression of softness.

Impossible to do at this level in-camera except for a few presets available with certain camera models, which makes it stand out as a post edit. Doesn't mean I wouldn't try it.