Depth of View preview

[DanK]

Thank you Richard, Dan, Alan and Ted for all this helpful information.

Dan - It’s good to know that experienced photographers like you and Manfred look to screen for feedback. Sure makes sense to me. I first heard about chimping -and not to do it - in Lynda.com. It might not be right for some photographers but it is very useful for me.

Maybe it comes from my work, which entails a lot of data analysis, but I generally don't throw out good information until I am certain I don't need it.

One other reason I look at the lcd is for the histogram. Some mirrorless cameras can be set to show the histogram in the viewfinder, but optical viewfinders can't do this. I have mine set so that I see separate histograms for each of the three color channels. (I also have the camera set to maximize the accuracy of the histograms.) This allows me to tell at the time whether I have exposure problems, rather than waiting until it's too late.

[Manfred M]

I use the focus peaking color to tell me where the DoF is going to be in a given scene.

Alan - it would surprise me very much if your camera acted that way, as that is not the way that this functionality is normally implemented. What is does show is where the focus plane is, and this is of course what the photographer is primarily interested in. Sharpness starts dropping off in front of and behind the focus plane and depth of field is little more than a range where sharpness is "good enough".

Try putting your camera to a test; set your camera to the largest aperture and see where the focus peaking areas are show. Now stop it down to the smallest aperture. In any mirrorless and video camera that have used that has implemented focus peaking, this does not change, even though depth of field does increase significantly.

Focus magnification, on the other hand, is a tried and true method of establishing focus in the film and video industry and is why photographers shoot tethered. This practice, especially when using a large monitor allows the photographer and videographer to verify focus.

[dem]

I just read about the DOV preview feature. My camera doesn’t have it, maybe because it is a bridge camera but I’m not sure. Do most cameras have this?

It seems a big advantage to mirrorless cameras that what you see in the viewfinder is what you will get.

Bridge cameras don't have this feature because it is of no use on a camera with a small sensor. You hardly have any room to adjust aperture in your bird example above - you are already shooting at f/5.6-f/6.4 wide open and closing aperture down to f/8 will noticeably deterriate image quality due to diffraction.

I don't think there is any benefit of stopping down your bridge camera at the telephoto end.

[CatherineA]

Maybe it comes from my work, which entails a lot of data analysis, but I generally don't throw out good information until I am certain I don't need it.

One other reason I look at the lcd is for the histogram. Some mirrorless cameras can be set to show the histogram in the viewfinder, but optical viewfinders can't do this. I have mine set so that I see separate histograms for each of the three color channels. (I also have the camera set to maximize the accuracy of the histograms.) This allows me to tell at the time whether I have exposure problems, rather than waiting until it's too late.

Dan - The histogram is the main reason that I use the screen, although I don’t glean all the information that you do from it. I mainly use it to see if I go off the screen at either end of the scale.

[DanK]

Dan - The histogram is the main reason that I use the screen, although I don’t glean all the information that you do from it. I mainly use it to see if I go off the screen at either end of the scale.

Catherine,

The reason I use all three colors is that sometimes one will blow out one color channel (that is, hitting the right-hand edge and clipping) even though the combined histogram looks fine. This isn't often a problem, but it can be with images that have a lot of one color. However, that's a fine point. Getting used to using the combined histogram is a good place to start.

Dan

[CatherineA]

Bridge cameras don't have this feature because it is of no use on a camera with a small sensor. You hardly have any room to adjust aperture in your bird example above - you are already shooting at f/5.6-f/6.4 wide open and closing aperture down to f/8 will noticeably deterriate image quality due to diffraction.

I don't think there is any benefit of stopping down your bridge camera at the telephoto end.

Thanks Dem! It’s true that I usually use only a small variation in the aperture and you’ve provided me with the explanation. And, as a bonus, I’ve now read an article on diffraction.

[dem]

It is quite easy to anticipate the effect of aperture on depth of field when you shoot birds, macro or portraiture, i. e. whenever focusing distance is much shorter than the hyperfocal distance. If you double f-number, the DOF also doubles. For example, if we go from f/4.0 to f/5.6 while keeping focal length fixed, DOF increases by 5.6/4.0 = 1.4 or 40%. The trade off of course is that we lose a stop of light and increase softening due to diffraction.

It is also relatively easy to anticipate how bad diffraction is going to be because it only depends on the f-number. If you do some test shots of a dollar bill or a small fluffy toy from about 3-4 meters away and compare them side by side, you might see that there is a small difference between f/4.0 and f/5.6 but f/8 looks noticeably worse.

One way to increase DOF is simply to zoom out - a loose framing will give you a wider DOF. Of course if you zoom out too much, you will lose some fine details.

There is not much room for maneuver either way. You can either zoom out a bit or stop down a bit. I find the telephoto range on my bridge camera (the Fuji X-S1) has been optimised to shoot wide open - stopping down 1/3 of a stop is fine but 2/3 is already taking the camera out of its comfort zone.

[William W]

Catherine

If your DoF concern is centred on resting bird shots, the answer is complex and simple. Complex because we don't know the lens you are using or how far away you are from the bird, and simple because you will more than likely have lots of shots that you can review and see what worked and what didn't..

For most practical purposes we don't need to know lens's FL or Shooting Distance: for any given Aperture, the DoF will be almost the same for the same FRAMING of the Shot.

So when Catherine is reviewing her pictures, (I expect) typically the FRAMING of the birds would be similar - thus easy to designate a typical Aperture to use most of the time.

Hence, the choice of ISO is really the main variable and that is used to establish the necessary Shutter Speed to arrest Subject Motion Blur.

I believe that we discussed Shutter Speed and Subject Motion Blur in a previous conversation.

WW

[pschlute]

I don't do a lot of wildlife shooting but when I do I use TAv mode on my camera (Pentax) so I can control aperture and shutter speed directly and allow the ISO to float. If I find the ISO is creeping too high for my taste I know I will have to sacrifice one of the other parameters.

[xpatUSA]

For most practical purposes we don't need to know lens's FL or Shooting Distance: for any given Aperture, the DoF will be almost the same for the same FRAMING of the Shot.

WW

Oh dear, Bill...

I've just posted quite the opposite here:

https://www.dpreview.com/forums/post/60546122

There I state that a particular shot, made with a 105mm lens, gives about double the DOF than an equally-framed, equal aperture shot made with a 50mm.

Clearly my spreadsheet mentioned therein is badly at odds with your statement and I'm not sure why that is.

Maybe because the object in the shots was at much less than the hyperfocal distance?

Apart from that, Merry Xmas!

[CatherineA]

Catherine,

The reason I use all three colors is that sometimes one will blow out one color channel (that is, hitting the right-hand edge and clipping) even though the combined histogram looks fine. This isn't often a problem, but it can be with images that have a lot of one color. However, that's a fine point. Getting used to using the combined histogram is a good place to start.

Dan

Thank you Dan. That is helpful for me to know. I had read that it is important to use a coloured histogram rather than a combined one but I didn’t know the reason.

[CatherineA]

It is quite easy to anticipate the effect of aperture on depth of field when you shoot birds, macro or portraiture, i. e. whenever focusing distance is much shorter than the hyperfocal distance. If you double f-number, the DOF also doubles. For example, if we go from f/4.0 to f/5.6 while keeping focal length fixed, DOF increases by 5.6/4.0 = 1.4 or 40%. The trade off of course is that we lose a stop of light and increase softening due to diffraction.

It is also relatively easy to anticipate how bad diffraction is going to be because it only depends on the f-number. If you do some test shots of a dollar bill or a small fluffy toy from about 3-4 meters away and compare them side by side, you might see that there is a small difference between f/4.0 and f/5.6 but f/8 looks noticeably worse.

One way to increase DOF is simply to zoom out - a loose framing will give you a wider DOF. Of course if you zoom out too much, you will lose some fine details.

There is not much room for maneuver either way. You can either zoom out a bit or stop down a bit. I find the telephoto range on my bridge camera (the Fuji X-S1) has been optimised to shoot wide open - stopping down 1/3 of a stop is fine but 2/3 is already taking the camera out of its comfort zone.

Thank you Dem! I have read and re-read this post and will experiment as you suggest later today. I had been thinking that a bit of a blurry background, when I can get it, might help a photo of a bird pop out a bit more rather than the bird being lost in the detail of the branches. It is true that I have little wiggle room in terms of aperture choice but still, it is very good to understand better the physics of the changes in settings - whether it is for birds or if I finally move on to try other subjects.

Your post also promoted me to read a short article on hyperfocal distance. It should help me take better landscape shots (at least if I re-read it and understand it better it should) http://www.vividlight.com/articles/3513.htm

[AlwaysOnAuto]

Alan - it would surprise me very much if your camera acted that way, as that is not the way that this functionality is normally implemented. What is does show is where the focus plane is, and this is of course what the photographer is primarily interested in. Sharpness starts dropping off in front of and behind the focus plane and depth of field is little more than a range where sharpness is "good enough".

Try putting your camera to a test; set your camera to the largest aperture and see where the focus peaking areas are show. Now stop it down to the smallest aperture. In any mirrorless and video camera that have used that has implemented focus peaking, this does not change, even though depth of field does increase significantly.

Focus magnification, on the other hand, is a tried and true method of establishing focus in the film and video industry and is why photographers shoot tethered. This practice, especially when using a large monitor allows the photographer and videographer to verify focus.

I've been known for thinking 'out of the box' Manfred. It may not be the way focus peaking was intended to be used, but I've had good luck using it the way I described.
Typically, the focus peaking color will illuminate in a band of color across the viewfinder. If say, I'm shooting a car and I want the whole car image to be sharp but I want the background to be blurred, I'll use the focus peaking to set the aperture such that the whole car is highlighted to the depth I want. I can then 'move' the focus peaking color back and forth with the focus of the lens and use focus magnification to hit the part of the car I want sharpest.
I guess it's all really about how you go about interpreting what the various tools the camera has to offer to get the shot you want.

[dem]

Oh dear, Bill...

I've just posted quite the opposite here:

https://www.dpreview.com/forums/post/60546122

There I state that a particular shot, made with a 105mm lens, gives about double the DOF than an equally-framed, equal aperture shot made with a 50mm.

Clearly my spreadsheet mentioned therein is badly at odds with your statement and I'm not sure why that is.

This is what you said:

I have a spread-sheet for macro work that takes an input of magnification, based on object size and how much of the sensor it occupies. For instance, it tells me for 300mm, 20mm at f/5.6:

f-length: distance, DOF

50mm: 800mm, 75mm

105mm: 1792mm, 157mm

Where distance is an output from the calculation, not an entered value.

Which confirms that, for equal framing, the 105mm has to step back to 1.8m from the object, thereby doubling the DOF - not lessening it.

If we use these subject-camera distances for the respective focal lengths and calculate DoF at f/5.6 on a full frame camera (CoC =0.03mm) using

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

we get 81.7mm for a 50 mm lens and 93.1mm for a 105mm lens.

There is a 11.4 mm difference which is there because I used your value of 1792mm which presumably was calculated from the sensor plane. If we calculate the camera-subject distance for a 105mm lens as 800 / 50 * 105 = 1680 mm (i.e. all distances are measured from the lens's optical centre), DOF calculator gives 81.5mm. Close enough to 81.7mm?

Maybe because the object in the shots was at much less than the hyperfocal distance?

That is exactly the regime where the DOF is a function of framing alone. Once the focusing distance gets close to the hyperfocal, then this rule doesn't quite work anymore.

EDIT. Ted, have you tried comparing your spreadsheet data to

https://www.photopills.com/calculators/dof-macro

To obtain the target magnification of 1:15 with a 50 mm lens, this calculator requires a sensor-subject distance of about 853mm (DoF = 81.39mm) and for a 105 mm lens it requires a sensor-subject distance of about 1792mm (DoF = 81.46mm). This is at f/5.6 and default values for full frame CoC and pupil magnification of 1. There is a few mm uncertainty in the sensor-subject distance due to the round up error for the magnification.

So for fixed framing/magnification two different websites predict the same DoF of about 81.5mm for either a 50mm or a 105mm lens.

[Manfred M]

I've been known for thinking 'out of the box' Manfred. It may not be the way focus peaking was intended to be used, but I've had good luck using it the way I described.
Typically, the focus peaking color will illuminate in a band of color across the viewfinder. If say, I'm shooting a car and I want the whole car image to be sharp but I want the background to be blurred, I'll use the focus peaking to set the aperture such that the whole car is highlighted to the depth I want. I can then 'move' the focus peaking color back and forth with the focus of the lens and use focus magnification to hit the part of the car I want sharpest.
I guess it's all really about how you go about interpreting what the various tools the camera has to offer to get the shot you want.

Actually, you are using Focus Peaking exactly the way it was designed. Focus Peaking is a focusing assist device, just like autofocus, focus magnification, etc. and it allows you to select where that focus plane lies in the image you are composing.

Once you have determined the focus plane the depth of field is determined by the distance to the subject and the aperture that is used. Depth of field is not influenced by the focusing method one happens to use. As long as the resolution is is less than the circle of confusion, the parts of the image in front of or behind the focus plane will look "sharp enough". The depth of field preview buttons stops down the lens to let us visually see the sharper and less sharp parts of the image; focus peaking does not have that functionality.

[pschlute]

If say, I'm shooting a car and I want the whole car image to be sharp but I want the background to be blurred, I'll use the focus peaking to set the aperture such that the whole car is highlighted to the depth I want. I can then 'move' the focus peaking color back and forth with the focus of the lens and use focus magnification to hit the part of the car I want sharpest.

That is a bit contradictory. If focus-peaking worked in the way you initially described, as you stopped down the lens the "peaky" bits would expand through the depth of the picture, ie all of the car would be peaking at f11 and only a small part at f2.8. Is that what you see ? Quite revolutionary if you do.

[AlwaysOnAuto]

Yes, Peter, that is exactly how it works.

[DanK]

I can't test this with my only mirrorless because it doesn't let me manually shut down the aperture, but it makes perfect sense to me. Focus peaking is supposed to show the areas with sufficient contrast to indicate acceptable exposure. It makes sense (at least to my naive way of thinking) that as one shuts down the aperture, DOF increases, and a larger portion of the image should be marked by focus peaking.

[pschlute]

Yes, Peter, that is exactly how it works.

Well blow me down. I don't have a mirrorless, but if I put my DSLR in Live View and use the DOF preview I get the same as you. The focus peaking extends throughout the scene. Logical really I suppose.

I can't see this changing the way I usually focus for a scene however which is with the viewfinder, but it may well have its applications, so thank you for that.

[Manfred M]

Yes, Peter, that is exactly how it works.

Interesting that it does not work like that on my Panasonic GX7; it shows the same area, regardless of what aperture I select. It looks like different manufacturers have implemented focus peaking differently.