Depth of Field: Larry Stewart: July 1, 1928 to June 26, 2019

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura) 06/28/2019 at 10:32 • Filed to: Photography

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I learned today that a s it happened, Private Stewart died the very hour we had our discussion Wednesday about this portrait of him.

Look at how this fellow’s left eye is sharp, but by the time you get to the tip of his nose, or back to his ear, the focus gets soft. I can only speculate what sort of camera might have captured this image, but I bet the f-stop (focal length / aperture diameter) was 1.0 or even less. (From Bruce’s photos)

Ash78, voting early and often > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:33

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Private Henri Bokeh died in the trenches of Belgium so that one day, soft focuses might bear his name forever.

/s

benjrblant > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:44

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but I bet the f-stop (focal length / aperture diameter) was 1.0 or even less.

highly, highly unlikely. fast lenses were huge, expensive, and uncommon. particularly during wwII, when money and resources were very scarce. likely this was shot on medium format and either the film or the paper under the enlarger was not perfectly planar which could result in the focus being off and someone didn’t want to waste resources by retaking or reprinting it.

Aremmes > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:44

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Actually, on large format cameras like what would’ve been used for this picture, the aperture likely wouldn’t have gone beyond f /5.7. These are cameras where a wide-angle lens has a focal length shorter than 160 mm (assuming 4" x5" negatives) .

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:45

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f-stop probably wasn’t that extreme, but the size of the plate was huge compared to any digital camera. Same as how f/2.8 on a full-frame camera has much shall ower DOF than a compact camera with a tiny sensor. Also , the focal plane was harder to align, so lots of old photos had a tilt-shift effect further modifying the DOF.

My wife and I had a portrait taken on glass plate for one of our anniversaries. It's an awesome keepsake. 

The Ghost of Oppo > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:48

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It’s been a while since I’ve printed, but if I remember correctly, you could change the field of depth by stopping down the aperture on the photo enlarger.

Rusty Vandura - www.tinyurl.com/keepoppo > benjrblant 06/26/2019 at 10:52

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I think that is a very reasonable hypothesis, but for the fact that the subject’s nearer eye is the point of focus, which could be intentional. You may be an expert in this area, but I’ve also spent time experimenting with focal length and that result looks like 50-80 mm and like f/1.2 @ 35mm. Now, medium format or whatever, or lens technology from 70 years ago could be an entirely different kettle of fish.

Rusty Vandura - www.tinyurl.com/keepoppo > Aremmes 06/26/2019 at 10:54

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In 35mm terms, I’d have guessed 50-80mm focal length and f/1.2. I’d be curious to learn how that would translate to 4" x 5" format.

Rusty Vandura - www.tinyurl.com/keepoppo > Bryan doesn't drive a 1M 06/26/2019 at 10:57

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I’ve experimented with f/1.4 on a full frame DSLR, and f/1.2 on old school 35mm bodies. So from what you and others have said here, sounds like there’s another factor having to do with the huge negative relative to aperture size and focal length and I don’t understand the geometry of that well. Have to do some looking.

Aremmes > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 10:58

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50 * 162/43 = 188

80 * 162/43 = 301

So between 188 and 300 mm.

Rusty Vandura - www.tinyurl.com/keepoppo > The Ghost of Oppo 06/26/2019 at 10:59

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Interesting. Also, as some have pointed out, there’s the massive negative size (4" x 5") relative to the size of the lens. I wonder whether what you’re describing here is the same thing at the other end of the process.

thejustache > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 11:00

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Someone else has already said this, but the larger the sensor the greater the depth of field. Once you get a big enough sensor (or film in this case) you can get extreme DOF even with relatively ‘slow’ lenses . Most likely those were taken on a 4x5 view camera, which would have been pretty common for studio portraits up through the ‘50s. Here is my Graphic View camera from the late 1940s

The other thing about a camera like this is it allows movements - you can tilt and shift the lens to be at a different plane than the film. This lets you be extremely selective about what is in focus and what isn’t - like in your shot where one eye is in focus but the other isn’t. It was pretty common in the day to take portraits with a small tilt so eyes were in focus, but the sharpness dropped off once you got down below the head. Here’s a portrait I took of a friend last year, using an f5.6 lens no less

An f1.0 lens would be nearly unshootable on 4x5 film. Even for medium format the fastest lens you find is usually f2.8.

EngineerWithTools > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 11:01

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This isn’t germane  to the conversation, but...

I read this as you photographing 70 year old kettles of fish. Thank goodness smell-o-vision never caught on.

Censored > Aremmes 06/26/2019 at 11:03

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Yep, this is why the H asselbla d (or other brand) medium format cameras can produce some crazy short DOF’s on relatively slow lenses and why on cell phones, you’ll see wide apertures (1.2 or 1.8) and still have the complete frame inside the DOF due to the tiny sensor size . I remember somewhere a calculator that let you input sensor or film size, focal length and aper ture and it would spit out the dof. I t was fun to play around with large sensors and very wide apertures and have dof’s around 0.5 mm. Try focusing that.

Rusty Vandura - www.tinyurl.com/keepoppo > Aremmes 06/26/2019 at 11:06

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I understand the arithmetic, but I don’t understand where the 162/43 ratio comes from.

By “translate,” what I really meant was how the size of the lens relates to the giant size of the negative, relative to 35mm SLR and DSLR bodies.

You are probably an expert in these things while I am only a practiced amateur .

Aremmes > Censored 06/26/2019 at 11:07

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This is the DOF calculator you’re looking for:

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

Aremmes > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 11:15

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162/43 is the ratio of the frame diagonals between 4"x5" and 135 format. Literally, a 4"x5" negative measures 162 mm corner to corner, while a 135-format negative measures 43 mm diagonal. The diagonal distance determines the focal length of a normal lens for a given negative size (hence the focal length of the smc Pentax-FA Limited 43/1.9, or why 6x 4. 5 and 6x7 medium-format cameras have 75mm and 105mm normal primes, respectively ).

Rusty Vandura - www.tinyurl.com/keepoppo > thejustache 06/26/2019 at 11:16

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Thanks for taking the time to post that. Obviously, in the picture you posted, the lens opening is MUCH smaller than the size of the negative plate (or sensor).

There’s always a risk in a forum like this of sounding like an idiot. I am a practiced amateur, but no more, though for more than 40 years. I started out with an Instamatic and my first SLR was a Pentax Spotmatic. Remember the days when ISO (ASA) 400 was considered fast? The standard lens on the Pentax was a 50mm f/1.2.

Now, thanks to your explanation, I understand what “tilt-shift” is and how it was used.

I use a Sigma f/1.4 50mm prime lens on a first-generation Canon 5D body and a photographer friend (actually a high school photography teacher) told me that the nearest eye was the place to concentrate the focus in shallow DOF situations and that’s the point of view I was coming from when I made my initial post.

Rusty Vandura - www.tinyurl.com/keepoppo > EngineerWithTools 06/26/2019 at 11:18

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thejustache > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 11:35

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Happy to share what I know, I’m no more than a practiced amature myself but I really enjoy it. Honestly before I got my 4x5 camera 2 years ago I’m sure I would have assumed the same thing. As to the point your friend makes, it’s true - unless you’re purposely going for some kind of effect the eyes are the focus point in a portrait as that’s what we’re drawn to as humans. For this photo I would guess it was a combination of the large sensor size and the need to probably photograph a big group of soldiers quickly that led to the effect, rather than a deliberate shift of the lens. It would be hard to know for sure though.

I love the old Pentax cameras and lenses. I have a spotmatic with the radioactive 50mm f1.4 I still shoot with sometimes, and my main digital rig is a Sony a6000 with an adapted 50mm f1.7 pentax k lens. It’s hard to beat a good fast 50 in my opinion!

Rusty Vandura - www.tinyurl.com/keepoppo > Aremmes 06/26/2019 at 11:44

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Is this related to your work? You seem highly knowledgeable.

Yes, thanks to Brother Pythagoras, I can find   the 162mm diagonal measurement on the 4"x5". Likewise, I can calculate the diagonal lengths of the 6" x 4.5" (~ 190mm) and the 6" x 7" (~ 234mm) negatives. What I cannot figure out is how these relate to the “ 75mm and 105mm normal primes.”

I do know that on my first SLR camera body, a Pentax Spotmatic KM, the “standard” lens was 50 mm, which would be ~1.2 x 43 mm, and that was stated as an f/1.2 lens.

So would the 75mm lens on the 6 x 4.5 be an f/2.5?

The 105mm on the 6 x 7 be f/2.2?

Rusty Vandura - www.tinyurl.com/keepoppo > thejustache 06/26/2019 at 11:47

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I produced the high school yearbook where I taught the yearbook class, for five years, and worked hard at developing my skills shooting people. I am at the limits of my gear and my time to develop my skill any further, so what I know I’ve codified into a personal body of best practices and put all the extra effort into composition and poses, and with some luck, I get pictures much nicer than those of the average bear. What they’re doing with cell phone cameras nowadays is mind boggling.

Aremmes > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 12:24

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Nothing to do with my day job, really. I work in IT.

Medium format sizes are typically metric, so 6x4.5 means 6 cm x 4.5 cm, and 6x7 means 6 cm x 7 cm. This gives the 75 mm and 105 mm diagonals, respectively. Lenses in those focal lengths usually have maximum apertures of f/2.8.

What maximum aperture is available for a given focal length isn’t really directly related to focal length or frame size and more to do with engineering and manufacturing constraints. It gets a lot harder to correct aberration and distortion when lens elements approach the diameter of a Big Gulp cup.

diplodicus forgot his password > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 12:57

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It doesn’t have anything to do with the f stop. It’s about the sensor/film size

https://fstoppers.com/education/understanding-how-sensor-size-affects-depth-field-312599

Rusty Vandura - www.tinyurl.com/keepoppo > Aremmes 06/26/2019 at 13:19

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Centimeters... Who knew?

Let me look again at those numbers. The idea of the diagonal of the sensor being the focal length is new to me.

Thanks for all of the info.

Only Vespas... > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 19:11

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Ah....no. [ the justsache] The larger the film plane/ sensor size the less depth of field. 35mm ha s less than 16mm. Some 8mm lenses one does not even have to focus. Tiny sensor, focus not an issue. That’s why the Canon 5D with a full frame sensor was so popular...dreamy soft then suddenly in focus shots. The 5d ’s brother, the 7d,  has a 3/4 sensor and depth of field is less of an issue [Easier to focus, especially during documentary shooting.]

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 19:58

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“Normal” focal length refers roughly to when the focal length matches the diagonal of the sensor. So, commonly 50mm on 35mm film. Longer than that is tele and shorter is wide.

Its unfortunate that focal length became the standard spec when angle of view is actually the relevant metric.

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/26/2019 at 20:07

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Depth of field is tricky when comparing different film/sensor formats. It’s dependant on focal length and distance to the subject (mostly). So a bigger sensor means that for a given focal length (85mm for example) the field of view will be wider. That means for an “equivalent” photo compared with a smaller sensor, the subject has to be closer, resulting in shallower DOF.

TL:DR - if everything else is equal, increasing sensor size decreases DOF.

Rusty Vandura - www.tinyurl.com/keepoppo > Only Vespas... 06/26/2019 at 23:28

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My go-to camera is a 5D with a Sigma f/1.4 50mm prime. And I can get some buttery bokeh with that. In fact, the lens is so fast that I don’t even try to use it out doors in sunshine. I owned a 7D, but I just never grooved with it. Never could get any comfort level with the video, either... I used a Sigma 35mm with that one; sold the body to my brother — we know him here as Ttyymmnn — who is rapidly becoming a very skilled photographer.

My favorite crop body is the 50D.

I’ve never fully understood the focal length thing and this thread has been an education!

Is this stuff part of your work?

Rusty Vandura - www.tinyurl.com/keepoppo > Bryan doesn't drive a 1M 06/26/2019 at 23:29

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So a larger sensor/film plane lessens  the angle of view?

Rusty Vandura - www.tinyurl.com/keepoppo > Bryan doesn't drive a 1M 06/26/2019 at 23:37

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I think you’re getting to the heart of the matter here with an explanation of what I got wrong in my original post.

I’ve been an avid amateur photographer for more than 40 years, but I’ve run out of enough free time — and money — to really develop my skills any more than they already are. I look at my skills and experience as a body of best practices and apply them and cross my fingers.

That means for an “equivalent” photo compared with a smaller sensor, the subject has to be closer, resulting in shallower DOF.

When I use my cell phone (Pixel 2) to take a picture, I like to stand off a few feet and zoom in a little. The field of view is so wide that it sort of puts the subject on a bubble and a little bit of zoom lessens that effect.

I need to ponder all of this some more...

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/27/2019 at 02:45

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Opposite, a 50mm lens on medium format would have greater angle of view (wider).

For example, I have a m43 camera with a smallish sensor and 25mm lens is “normal”. On full frame or 35mm film, a 25mm lens is pretty wide.

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/27/2019 at 02:52

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I was lucky and took an optics class in college during the peak of my photograhy enthusiasm. It helped everything click into place in my head.

Now that I have a daughter, I love taking pictures, but my focus is on capturing a moment rather than technical stuff. And I use my phone for 99% of the pictures...

Rusty Vandura - www.tinyurl.com/keepoppo > Bryan doesn't drive a 1M 06/27/2019 at 07:26

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If the focal length of a lens matches the diagonal measurement of the sensor (either digital sensor or frame of film), the n that is the normal lens?

Diagonal measure of sensor determines “normal?”

(Checking my understanding...)

Bryan doesn't drive a 1M > Rusty Vandura - www.tinyurl.com/keepoppo 06/27/2019 at 21:48

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Yep, that's correct. And it just happens to match up with what our eyes normally see.

davesaddiction @ opposite-lock.com > Rusty Vandura - www.tinyurl.com/keepoppo 06/28/2019 at 10:39

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That’s... eerie.