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04-05-2016, 04:31 PM   #1
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Understanding Aperture: Manual vs Auto

Hey Everyone,

I’m fairly new to photography and trying to get the basics down.

I’m using a *ist DS with a 50 mm 1.7 in this example, but this is consistent with my other lenses.
I have also went through the custom settings to allow my camera to take a photo when the aperture ring is on a setting other than auto.

When I set my camera to aperture priority mode at 1.7, and set my lens ring to auto, I get an image with nice bokeh. Also, when I set my camera to auto mode, and set my lens ring to a 1.7 aperture, I still get an image with nice bokeh.

But, doing the opposite exercise, I can set my camera to aperture priority at 22, and set the lens ring to auto, I get an image with the background in focus. BUT, when I set my camera to auto mode, and set my lens ring to a 22 aperture, I end up with an image without a background in focus and has nice bokeh.

Why is this happening? I would image that if I have the lens ring set to 22 aperture I should be getting a focused background… Am I missing something here?

Thanks for your help!

04-05-2016, 04:45 PM - 1 Like   #2
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QuoteOriginally posted by FozzFoster Quote
BUT, when I set my camera to auto mode, and set my lens ring to a 22 aperture, I end up with an image without a background in focus and has nice bokeh.
You should always have the ring set to "A" on DSLRs, since they're not designed for aperture ring use if there's an A setting available.

Adam
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04-05-2016, 04:51 PM   #3
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QuoteOriginally posted by Adam Quote
You should always have the ring set to "A" on DSLRs, since they're not designed for aperture ring use if there's an A setting available.
Hi Adam,

Thanks for the quick response,

I was under the impression that this was a valuable setting to have on a lens, as with it you can set the aperture while using extension tubes.
It is one of the cons of many lenses without an aperture ring in their reviews.

What's the point of having a aperture ring if you only use dslrs?

Is it that the aperture ring engages when the lens isn't in physical contact with the body; using an extension tube?

Thanks again
04-05-2016, 05:04 PM - 1 Like   #4
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QuoteOriginally posted by FozzFoster Quote
Hi Adam,

Thanks for the quick response,

I was under the impression that this was a valuable setting to have on a lens, as with it you can set the aperture while using extension tubes.
It is one of the cons of many lenses without an aperture ring in their reviews.

What's the point of having a aperture ring if you only use dslrs?

Is it that the aperture ring engages when the lens isn't in physical contact with the body; using an extension tube?

Thanks again
You can make a lens with out an A setting work by using "green button" metering. Essentially the DSLR needs to be in M mode and you make it take a stopped down reading at the aperture you have set. Otherwise the camera ignores the aperture ring. If you use bellows, reversed lenses, extension rings etc having the aperture ring will be very useful but you may be metering wide open and then calculating your exposure if the method you use doesn't allow you to meter stopped down.

Just understand that when you want to control aperture - you do so from the camera not the lens when using Pentax DSLR's. There are some film era bodies that can use the A setting or the lens aperture ring but the ability to do that was removed over time due to constraints.

04-05-2016, 05:27 PM - 1 Like   #5
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QuoteOriginally posted by FozzFoster Quote
What's the point of having a aperture ring if you only use dslrs?
There isn't one, unless you're using manual extension tubes, bellows, or reverse mounting, in which case the diaphragm is controlled by the aperture ring alone and not by the camera's actuator.

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04-05-2016, 05:55 PM - 1 Like   #6
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QuoteOriginally posted by FozzFoster Quote
What's the point of having a aperture ring if you only use dslrs?
QuoteOriginally posted by Adam Quote
There isn't one, unless you're using manual extension tubes, bellows, or reverse mounting, in which case the diaphragm is controlled by the aperture ring alone and not by the camera's actuator.
One other use case that is not obvious if we limit our discussion to Pentax is that most (all?) K-mount and M42 mount lenses may be adapted to Canon crop-frame dSLR cameras. With the exception of certain high-priced adapters, the lens must have an aperture ring and be capable of full manual aperture operation. The same is true with the various mirrorless (non-SLR) interchangeable lens cameras.


Steve
04-05-2016, 08:12 PM - 1 Like   #7
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To use the aperture ring (not A setting) camera should be in M mode. Then all should be fine: whether it is a K lens (K,M,A,F,FA) or a M42 lens set (on the lens) in manual (not auto).

Although correct, I should add w/ M42 lens in manual (not auto) AV mode can be used, as the lens aperture is in a fixed position and does not require the camera to actuate anything on the lens. Zone focused with a wide FL lens (I use w/ 28mm and wider) this is a very convenient, powerful, fast method.

Last edited by dms; 04-06-2016 at 08:27 PM. Reason: make the camera operation w/ M42 lens less restrictive
04-06-2016, 04:26 AM - 1 Like   #8
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As I understand it, all K, M, A, F, FA etc type lenses are 'auto- aperture' .... This means that they default to the widest setting when attached to a camera body with the coupling.

This allows easier focusing. The camera 'stops down' the aperture when the picture is taken, or the DOF (optical) preview is used. It is not possible to manually stop down these lenses when coupled to the camera. So you can't use them with tubes that have no contacts.

There are other lens types that have a 'manual/auto' switch ....in auto they function as described above, like K, M, A, etc types. In manual the aperture will not couple to the camera, and the camera cannot automatically stop down the lens .... The aperture remains fixed in the setting put on the aperture ring. This is handy for using tubes without contacts. My Tamron Adaptall 135mm f2.8 (CT135) works like this and is very useful. In 'auto' mode I can use it as a K - type lens with stop down metering, or in manual aperture mode with the tubes.

04-06-2016, 07:01 AM - 1 Like   #9
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QuoteOriginally posted by Adam Quote
There isn't one, unless you're using manual extension tubes, bellows, or reverse mounting, in which case the diaphragm is controlled by the aperture ring alone and not by the camera's actuator.

Just for personal preference I really wish it did have a use, when I took a photography class back in the dark ages (25+ years ago) I used an old Spotmatic F.

Using that I got used to the idea that my Right hand controlled the shutter, adjusting the shutter speed and when to take the picture
My left hand controlled the lens, the focus point and the depth of field.


I understood that when I adjusted one I would have to adjust the other to maintain the proper exposure, i.e. if I knew I wanted more depth of field I would adjust with my left hand, and at the same time I would have to slow the shutter down with my right.
There might be times when I would have to live with a slightly off exposure picture due to needing more/less aperture/shutter speed to get the intended result that I would have to adjust in post

Using my K-r (I know its old) which only has one adjustment dial, full manual mode is pretty difficult. its not intuitive to adjust one (i.e. aperture) and then click another button to switch to adjust the other (shutter)

I know the higher end and newer cameras have two adjustment dials but I still prefer the idea of one hand controls the lens and one the shutter, it just makes more sense in my mind.

But then again that is personal preference.
04-06-2016, 07:47 AM - 1 Like   #10
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I feel your pain; I spent almost 30 years looking through an MX and developed the same kind of shooting style. Even now when I'm used to two-wheel shooting with shutter speed on the front dial and aperture on the rear, it still feels vaguely odd, especially when I have a plastic fantastic prime on, and consequently my left hand does ... nothing - except support the camera, and not get in the way of the focusing ring as it turns!
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