Shallow Depth Of field

[Clemontz]

hi! asking for help for my 50mm color-skopar and 75mm heliar...

how is it tt my pic s alwaz turns out wif too shallow depth of field? like if the person's face is focused... his shoulder could be off.. say he's facing the cam but leaning abit to the side.
hmm... how do i achieve grater depth of field.. standoff further?
but doing so will affect my compositon ... i noe there's the depth of field scale on the lens for reference..

currently using a R body.and proud owner of 15mm, 50mm and 75mm


Pls help!
thanks
😀

 

[pvdhaar]

Re: Shallow Depth Of field

hi! asking for help for my 50mm color-skopar and 75mm heliar...

how is it tt my pic s alwaz turns out wif too shallow depth of field? like if the person's face is focused... his shoulder could be off.. say he's facing the cam but leaning abit to the side.
hmm... how do i achieve grater depth of field.. standoff further?
but doing so will affect my compositon ... i noe there's the depth of field scale on the lens for reference..

The depth of field scales by themselves do nothing, you have to select an appropriate aperture. From your description I guess that you've got the lenses set at their maximum aperture (that is the lowest number). Turn the aperture dial to a larger number, for instance 8, and you'll find that the depth of field increases as indicated on the depth of field scale. Make the aperture as small as possible (largest number, 16 or so), and the depth of field will be at it's maximum.

Success😉

 

[bmattock]

Remember that when you open the aperture (f-stop setting), you also have to increase the shutter speed to compensate, so that the exposure remains correct. If you stop the lens down, you have to decrease shutter speed to let more light in. The issue as far as the film is concerned is how much light reaches the film for a photograph. To the film, it doesn't matter if the lens lets in lots of light (open aperture) for a short period of time, or less light (closed down or stopped down aperture) for a longer period of time.

Depth of field is increased when the aperture is very small - but more so for shorter lenses. Therefore, a 35mm lens will have greater depth-of-field for a given f-stop than a 50mm lens or a 75mm lens.

Some people like to intentionally use depth-of-field effects (known then as differential focus) to bring attention to a certain part of the photo - what you want the viewer to concentrate on is sharp, the often-distracting background is blurred out intentionally.

You can use depth-of-field effects to your benefit, whether you want to be sharp from front to back, or only focused on a certain point in your photo - the choice is yours (if you camera has manual control/override). I use both, depending on circumstances.

Best Regards,

Bill Mattocks

 

[Stu :)]

Re: Re: Shallow Depth Of field

Re: Re: Shallow Depth Of field

Also remember that the focal length of you lens and the distance between your subject and lens will also affect you DOF.

The longer focal length lens you use, the less DOF it has. For example you may noticed that when you take photos with your 15mm set to f8, that EVERYTHING from 3-5ft to infinity is in focus. However on your 75mm set to f8, if it is focused at 3ft you'll get only a couple more inches to the front and rear of the subject in focus as well. Look at some of the sports action shots in your local newspaper. Most of these where photographed using very long lenses (200mm to 1200mm) and the DOF falls off quickly.


Also the closer to your subject, your DOF will also drop off. The further back from your subject the DOF will increase.

I will however have to override Peter's comment on the depth of field scale.

The depth of field scales by themselves do nothing, you have to select an appropriate aperture.

In fact there are there for a jolly good reason. For something called the Hyperfocal Distance.

http://dfleming.ameranet.com/hyperfocal.html http://www.vividlight.com/articles/3513.htm

The above links are have bit more info, ignore the math unless it really flicks you switch. Or just cut and paste into Google and go nuts.

But basically when you set you aperture (example f8) and focus your lens, the numbers on your DOF scale will line up. Look at DOF scale and you'll see a set of numbers that correspond with your lens apertures. Look at the scale for f8 (there should be one either side of the focus point. From this you should be able to see what you DOF is going to be. From this you can increase or decrease the aperture size if you wish to get the desired DOF.
This can be used in many different ways. If you want to take a photograph that has two different subjects a distance apart, focus one, note the focus point, focus on the other subject, note the focus point and then select the correct aperture that will put both subjects into the DOF you require. Even though both subjects will look out of focus in the viewfinder/prism/ground glass, but far as the optics inside the lens/camera are concerned it is in focus. The same rule can be used in reverse for something different.

After a while of doing this (especially in 35mm) you'll learn DOF of each lens you use and start to choose the correct aperture for the picture you want to take.

Look at my photo titled 'Construction Zone' in the gallery section. A good example of the hyperfocal rule being used.

Go buy a roll of film and go nuts...

Stu 🙂

 

[HelenB]

Some more...

The DOF scale doesn't really tell you if something is in focus. It just tells you what isn't noticeably out of focus in certain circumstances. A subtle, but important, difference. If you are critical about it, use the markings for the aperture one stop wider (ie the next lower number) or even two stops wider.

The better the rest of your technique, the more this matters. If you are using fine grain or high acutance film, a tripod and much enlargement, the DOF markings will not be good enough. Conversely, if you are using coarse grained film and slow shutter speeds handheld, you will have more apparent focus if the grain is sharp in the print. This is one of the reasons that my pictures of people work, even though taken at f/1 and 1/4 sec on EPJ transparency film pushed three stops to EI 2000. There's nothing in sharp focus except the film grain, and that gives the picture an apparent sharpness that it wouldn't otherwise have.

There is a school of thought that says that you should almost always focus at infinity for landscapes. I often see fuzzy horizons on pictures where the lens has been set at the hyperfocal distance. This guarantees that the horizon is not in sharp focus.

Helen
I blur like sotong lah

 

[Huck Finn]

Whoa, Helen. You're over my head & I'd like to learn more.

Please explain: "If you're using a coarse grained film . . . you will have more apparent focus if the grain is sharp in the print. This is one of the reasons that my pictures of people work . . . There's nothing in sharp focus except the film grain . . ." How do you get coarse grained film to the point that "the grain is sharp in the print?"

Also what are "high acutance film," "EPJ transparency film," & "EI2000?"

Sorry, but you'll have to bear with me. I'm pretty much of a neophyte who is just trying to learn. Thanks

 

[ZeissFan]

Basically, you need to use a smaller aperture. That will increase depth of field.

Moving back a step or two from your subject also will increase depth of field, as will the use of a wide angle lens.

 

[HelenB]

Hi Huck,

Thanks for asking the questions - if I wrote the whole speel to begin with I could spend hours - not a good thing. I prefer to gloss over things, then go into detail if asked.

Using low resolution, coarse grained film:
There's something I didn't mention. Maybe I should take a step back...
The idea of depth of field is all about how much an image can be blurred before you notice that it is blurred. For example, imagine a tiny tiny point of light being focussed onto the film. If it is in focus it will show as a tiny tiny point of light. If it is out of focus it will appear as a circle. The question is: how small does that circle have to be before it looks like a point?

So, we have our circle of light on the film. A fine grained, high resolution film will record the fact that it is a circle because the circle covers, say, ten 'grains' of film. A coarse-grained, low resolution film might not record it as a circle, because the circle is the same kind of size as the film 'grain'. and thus only one or two 'grains' are covered by the circle. This means that the film itself doesn't show the point of light to be so obviously out of focus.

The next thing is apparent sharpness. This is quite an important effect. An observation: a film with fine, 'mushy' grain may not look as sharp as a film with coarse, distinct grain. The fact that the eye sees something that is tack sharp (eg the clearly defined clumps of silver) sends the subliminal message 'this picture looks sharp' to the brain. Often the viewer will be unaware of this effect, it is so subtle. The grain need not be obvious - the eye picks up clues.

For colour, the differences between Fuji films, most Kodak films and Kodachrome is a classic example. By and large, Fuji go for low aparrent graininess - indistinct clouds of dye that give a smooth appearance. Kodak prefer a bit more bite - more defined clouds of dye that look sharper, but also look more grainy. Kodachrome goes the whole way: quite grainy for the speed, but very sharp looking.

Dye clouds: the image in colour materials is formed from transparent clouds of dye.
Graininess: strictly speaking it is better to refer to 'grainy' and 'graininess' rather than 'grain' because you may not be referring to the actual grain of the film (which may not be perceptible) but the appearance of clumps of grain. I have used 'grain' for 'graininess' for the sake of brevity and simplicity.

Acutance: very difficult to define, impossible to quantify. It is the film's ability to make sharp edges look sharp. It is similar to the effects of unsharp masking in Photoshop or the sharpening used in digital cameras. A film with poor acutance will make a sharp edge between a dark area and a light area look grey. A film with high acutance would emphasise the edge by making the dark side of the edge darker and the light side of the edge lighter. I have some Delta 400 developed with too little agitation (by accident) that looks painfully sharp because of this. I say painfully because you can see the dark/light lines around details as if I'd used too much unsharp masking in Photoshop.

EPJ: just Kodak's code for Ektachrome 320T, an ISO 320 tungsten-balanced (ie it gives the correct colours under incandescent lighting) film. EPJ is quite a grainy film, especially when pushed three stops.

EI 2000: a film speed setting of 2000. Some might call it 2000 ASA, but, being a pedantic nit-picker, I have to call it EI 2000. EI is short for Exposure Index and is meant to be used for speeds that do not conform to the film's true speed as determined by a recognised standard (eg ASA, DIN or ISO). The EI number is usually in line with the ASA/ISO standard number. Pushing EPJ three stops would be EI 320 x 8 = 2500 in theory (OK, I'm sticking to the conventional speed steps, not the mathematically correct numbers) but few films deliver that well when pushed, so I set 2000 on my meter. Another example: when pushing Fuji 800 NPZ two stops (theoretically EI3200) I set 2000 as well.

Enough for now, back to work...

Ask if anything is unclear - this was a bit rushed.

Best,
Helen
PS "I blur like sotong" means "I'm as stupid as a cuttlefish" in Singlish (Singapore English), sotong being Malay for cuttlefish.

 

[Huck Finn]

Helen, thanks so much for the lengthy reply. I'll let you know if I have any questions after I've had a chance to digest it all. There's a lot there to absorb on the first reading. Thanks again!

 

[pvdhaar]

Re: Re: Re: Shallow Depth Of field

Re: Re: Re: Shallow Depth Of field

I will however have to override Peter's comment on the depth of field scale.
In fact there are there for a jolly good reason. For something called the Hyperfocal Distance.

I just saw Stu's remark, and he's perfectly right that the DOF scales are incredibly usefull. If I gave the impression that I they're not important, then my English must have been somehow off the mark.

I merely tried to indicate that DOF markings tell you 'what the lens does' given a certain aperture and focus, but it's up to you to actually set the aperture and focus.

 

[oftheherd]

Everyone has given good explanations above. I will try to add some things that I have read and learned, that have helped me understand things over the years. Hopefully I won't confuse the issue more. First, in answer to your question, basically, to increase apparent depth of field (dof), you must either move farther back, use a wider lens, or decrease the size of the aperture (or sometimes a combination of the three). Note that the scales on your lens are very helpful in that respect, as well as for using the hyperfocal distance. Note also however, that dof extends about 1/3 in front of the object plane of focus, and about 2/3 behind it.

The reason the above works is due to those little beasties, circles of confusion (cc). That has always been difficult for me to conceptualize, much less explain. Imagine a very large format camera, with a film size about 4x6 feet. If you place one eye at the film plane, and look out at the scene through the lens, you will only see a small portion, a small circle assuming your lens' diaphram is circular, of the entire scene. You can't see all of it. Just what you can see out that small circle. Any place on the film plane that you move and look out, up or down, or from side to side, you will see a small circle of the scene. All the circles overlap, as you can tell by moving around. If you could reduce the size of the aperture while you looked, of course, the circle you saw would get smaller.

This is of course, also what your film would see (of course, it is stationary). Now let's get back to a conventional sized camera. Imagine you are looking at a point of light in the scene your are viewing. Those cc are going to be a lot smaller than in the imaginary camera above. They will be quite small on a 35mm camera. I don't have any books here, but I seem to recall that a cc on 35mm film must be 0.003 to be considered sharp (remember, we may enlarge it 10 or 20 or more times for our print). The larger those cc from the optimum (0.003?), the more blurred they will be. It was a small point light source, remember? So if they are too large, they will be blurred. They may be very slightly blurred, or greatly blurred. The larger the lens aperture, the larger the cc. The smaller the lens aperture, the smaller the cc.

A lens of one focal length might have a viewing angle of 50 degrees. One with an angle of view of 75 degrees (a wider lens) would cover more of the scene in front of you. It has to bring all that area into the same film size. So, it has to make everything smaller if you will. That gives smaller cc, assuming good resolving power. You probably need to get a book that shows ray tracing to see it, but those wider lenses suddenly have to send the rays at a greater angle to the film. That is what causes the so called wide angle distortion. As the rays get farther from the center of the lens, they get more oval. Actually, you can sort of see this effect with a flashlight. Focus it to as small a point in front of you as you can, then swing it to the side. You will notice the round circle getting more oval the farther away from directly in front of you.

I also said moving back would get more of the scene if focus. If you keep the object plane of focus the same, but move back, you are now taking in more of the scene. You can see more on the sides (and of course top and bottom) than before. It still has to get all that on the same sized piece of film. There will be a convergence of all the light onto that same size of film, so the circles will be smaller.

Well, as I said, I don't have any of my books with me, so I hope I haven't said something wrong. If so, somebody please jump in and correct me. Also, please understand the above is a simplification to relate to cc, not to explain all about lens design, which I know nothing about anyway. Some terms may not be exactely correct for other facets of lens design. Again, I was hoping to make cc easier to conceptualize. It still throws me sometimes, so between my own lack with words, and my own conceptualization problems, don't feel bad if it doesn't make sense. :bang: