Auto and f stops.

Grandpa Ron

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Aug 9, 2018
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Not being particularly familiar with the thinking of the gurus that write the auto programs, I wonder why they choose a particular f stop?

I shot these two sunflower shots. The single flower was f 9 at 1/100 sec. with ISO 200. The second was also f9 but 1/200 sec. at ISO 100. Both if them lack depth of field. I would have preferred both flowers in focus on the second shot.

I know I can do a aperture priority etc. but my question is, has bokeh become the norm with close up shooting?


2 flowers .JPG
It's not that bokeh has become the norm, it's that short focus distances put a hard limit on depth of field.
I don't know, bokeh seems to just be a thing... I think whether the background's in focus or not so much, it's still there and can just show up as blurry blobs of color and shape. Best thing is for people to change their vantage point and try to get a better background rather than assume they can blur it (well, so it works).

I don't use auto, or do modes; I set the camera manually most of the time.

The second one looks off, too much bright sun from that perspective I think; it seems better from the angle and perspective used in the first. Probably a little later when the sun wasn't quite so directly overhead might have been better.

Instead of a faster shutter speed maybe try a smaller aperture for the second one. Or for the second one, you might have to adjust both (smaller aperture and faster speed). Even for the first one, I'd try a smaller aperture then adjust the shutter speed, and stay with 100 ISO (I see no need for 200 in that bright sun).

It seems like you know what needs to be done, so shooting manually might give you better control over what the camera does and better results.
In terms of depth of field, distance is one of the most important things --more important than focal length and somewhat more important than lens opening. For example at 600 ft at f 2.8 with a 300mm lens you have quite a bit of depth of field. Just off the top of my head I would expect that depth of field at f2.8 and a 600-foot focus point your depth of field will be miles literally. If you focus at 1 mile with a 300 mm lens, you will have depth of field that extends to the Moon

If on the other hand you focus at 3 ft an f 2.8 300 mm lens using a 26 mm extension tube your depth of field will be measured in millimeters.

Experience has shown me and many others that in order to get deep depth of field pictures we need to shoot at small apertures like F-16 or F-22, diffraction be damned. If we want shallow depth of field pictures then wide apertures make such pictures possible quite easily, and using lens openings like f / 1.8 to F/4 we get shallow depth of field. For general-purpose pictures, apertures such as f / 5.6 to f11 are often quite useful.
Years ago Canon invented the "A-Dep" or somesuch exposure mode:you would use the autofocus system to focus on the closest thing and the farthest thing that you wanted in focus and the system would compute the needed aperture for the focal length in was never very popular. This exposure mode fell out of use fairly quickly.
Hiya Ron
As to your first question/statement
The f stop, shutter speed, iso are all ratio that has to be balanced for the “ correct” exposure
Adjust one the one of the other two , sometimes both , have to be adjusted
Auto is good but it can’t think and some lighting conditions fool it

Ho w far apart are the two flowers,
There are DOF depth of field apps out there that you can use on phone etc older lenses used to have lines on to show
DOF at different f stops
It may de that the flowers are to far apart
Try picking a focus point that puts the front flower in the first third of focus and the back flower in the last two thirds
So a focus point forward of between the two
You will prob have to use manual focus, but this is digital we now have the opportunity to see the effects of trying something in real time and not having to wait until the film is developed
As for boken .... I have next to no interest in it so my knowledge is limited but it’s my understanding that the lens and how it’s made can have an effect
Bokeh is a result of DOF which as Derrel pointed out can vary based on distance from the subject and aperture. As I understand it all manufactures algorithms operate under the assumption that they take the average luminance in a given area and calculates an exposure that makes that part of the image rendered as a mid-tone, having the same luminance as 18% grey. So depending on your exposure mode setting (spot, multi, center weighted, evaluative) changing your distance from the subject can change the area the camera considers, which changes the average luminance of the area being considered.

Then you have certain hard rules that vary by manufacture things like use widest aperture at shutter speed below a certain number, and a database that's used to compare the values calculated to establish the ideal exposure for the "entire" frame.
I wonder if the camera "knows" what focal length lens was being used and making decisions based on that? If not perhaps there were assumptions made about what is "typically" used when the algorithms were written?

Personally, I almost always use aperture priority to the the depth (or lack of it) that I want.
I wonder if the camera "knows" what focal length lens was being used and making decisions based on that?

I can't speak for other brands, but Pentax cameras do. Not only that, but so does the new Pentax flash. Using P-TTL it automatically zooms to match the focal length, and communicates with the camera to provide the correct amount of flash based on camera settings.
Basically, at a foot-and-a-half or two feet from the subject, even at f:22 your depth of field is probably less than 6 inches. You just can't get big depth of field that close to the subject unless you have a very wide-angle lens

You can zoom back into the 20s for focal length and get a good increase in depth of field, but if you move in close to get the same framing, you lose that depth of field again, simply because of the close focus. However, if you zoom back into 20-some mm, shoot from the same distance and then crop the image, you get the same framing with increased depth of field. If you leave the zoom alone and move back, then crop that shot, you get increased depth of field but a flatter perspective. You just have to decide if you can afford to give up the resolution that results from cropping.

Keep in mind, moving towards or away from the subject changes the perspective, regardless of the focal length. Zooming out and cropping does NOT change the perspective, not zooming but moving away does change the perspective. Moving away and zooming out will both increase your depth of field, but which one you like depends on whether the change in the view from moving back is acceptable to your desired framing.
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From your EXIF Data, with your camera sensor size, APS-C and the lens used EF-S 18-55 @42mm;

If the foreground flower is at 63.2 cm then your DoF at F9 is only 7 cm which is likely too narrow to capture both in focus.

Let's be clear Bokeh is not a fad or the norm, it is the OOF blur characteristics of a particular lens. Before the word became de rigueur the character of blur was still evident. It's just recently that some people like shallow DoF at the expense of content but not all lenses draw OOF areas the same.
Just to add to the wonderment, the camera manual shows when I switch dial setting, I not only change DOF but also enhance certain colors. When in doubt it is back to Aperture priority.
The bokeh craze will pass.

i have been using alot of different type settings to achieve a particular feel to the image.
Part of it uses a T/S system (also bellows) to do the exact opposite. Create a closeup and wide open non-bokeh. This gives the image perspective, and not always does one need DoF.
The f stop is selected based on the amount of light. The camera is programmed for a minimum shutter speed to prevent blur at the lowest ISO. Once the shutter speed is calculated by the camera, and the ISO, it sets the aperture. Brighter light, smaller aperture. Darker light, larger aperture.

Your camera may have settings where you can adjust the automatic settings to prevent ISO, aperture and shutter speed to be limited to certain settings. For example, you can still be on auto, but have the shutter not go below 1/250. That's handy of you're shooting sports. You can do similar things with aperture and ISO. Check your manual to see if these settings are available. They might help. Good luck.
Firstly, don't confuse 'bokeh' with depth-of-field.

If I take a picture of two sunflowers (which are some distance apart) with my Nikon lens at f/2.0 then the one I'm not focused on will be out of focus (OOF).

If I swap the lens for an old Orikkor, and take the same shot at f/2.0 then the two images will show the same depth of field - flower one in focus, and flower two being out of focus to the same extent. That's depth of field for you. Many photographers use selective depth of field to highlight a particular part of an image.

If I want you to look at one flower, I'll use a wide aperture to emphasise it. If I want you to look at all the flowers in my garden I'll use a smaller aperture like f/16 or f/22 even.

However, these two lenses have different ways of rendering the out-of-focus bits (most notable the highlights) - the Nikon, like most modern lenses, shows these in a very neutral way, whereas older lenses generally have different characteristics - my Orikkor shows OOF highlights in what I think as quite an unpleasant way (others disagree), but something like an old Helios is said to have much more pleasant rendering.
That's why the price of old lenses is going up - people like the way that they render the OOF highlights. This is Bokeh - it's the quality of the OOF bits of the image, not just how much is in or out of focus.

Hope this helps!

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