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Aperture setting


djnibler

Question

Using 3.2.2 Premium with a 450D. This is probably more of a general photography question than a BYE question, as I know little about photography and only got into it for astrophotography purposes so the learning curve is extra steep for me. But the question I have is about the actual difference between shutter speed and aperture. I've read up on it and I understand the difference (I think) for regular cameras, but I don't really understand it for DSLRs since there is no real aperture. I know I can set both of these in BYE. Obviously changing the shutter speed will literally change the amount of time the camera sensor is exposed, which changes the exposure of the resulting picture. I'm sure it's wrong to use the term "brightness" but that brightness increases with longer exposures, of course. But then I get confused about aperture. Is the camera simply using a formula to increase the "brightness" of the image captured based on the aperture setting?

My question was originally going to be, what aperture setting should I be using if I have my camera connected to my telescope? My guess it that I set it to whatever the focal ratio of that telescope is - in my case, it is f/10. So I should set BYE aperture value to f/10 and then use shutter speed to control exposure correct? Is there any reason I would ever want to use the aperture value to control exposure/"brightness" when using a telescope as my lens?

 

Thanks in advance and sorry for the newbie question. 

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Sorry, but you are incorrect to say that "for DSLRs there is no real aperture." There is, and you can set it from BYE...under 2 conditions.

1) the camera must be in Manual mode. If it is in full Auto or Program mode, for example, the camera controls the aperture so it makes no sense for BYE to try to do so.

2) there must be a lens attached to the camera that allows its aperture to be adjusted by the camera. Canon EF lenses support this, but other lenses may not.

Aperture and shutter open duration control the amount of light that reaches the sensor. The larger the f-stop value, the smaller the aperture and the less light can get to the sensor for a given exposure duration. The lens typically has an iris that closes when a picture is taken and re-opens after the exposure is complete. It works in conjunction with the shutter (on cameras with a shutter).

One other effect of aperture is that it also controls the depth-of-field. This is the range of distances that are in focus at any given time. With a larger F-stop value, the depth-of-field is increased. So shooting at f/16 will have a greater depth-of-field than shooting at f/6. This might lead you to think that if you are using your camera and lens for astrophotography that you would want to shoot at the widest f-stop that the camera supports since everything is at infinity, but it is typical to close the iris a couple of stops to avoid other optical effects, like trailing or blobby stars in the corners.

A telescope has a fixed aperture and since BYE recognizes that the camera is connected to a "lens" that does not have an adjustable aperture, it does not provide an aperture setting in the Capture Plan Center. You might also notice that If you add or remove a lens from the camera when BYE is connected, you need to Disconnect and re-Connect BYE in order for aperture to be hidden or shown as a column in the capture plan.

I hope this helps.

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Thank you very much for the fast, informative, and detailed reply. 

So a couple follow-up questions - I always have the aperture setting option in BYE - even when I have my camera connected to my telescope which has no adjustable aperture. My scope is an 8" SCT with manual focus knob. When using the imaging or focus functions of BYE, and camera set to M mode, I can always set the shutter speed and the aperture. For a given shutter speed, changing the aperture setting in BYE results in changes to the exposure of the image that is captured. My 8" SCT telescope has a focal ratio of f10 - so does this mean I should configure BYE's aperture setting to f10, and control exposure with shutter speed alone? Or should I juggle both, and if so, any guidelines for how I should prioritize between the two?

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With my T5i I cannot cause the aperture dropdown to display in the Capture Plan Center or the aperture setting in the Camera Information Center unless I have an adjustable lens mounted on the camera. With a body cap, the aperture is not displayed in either location. I am wondering if there is a problem with your camera.

The focal ratio of the telescope and the aperture setting of the camera are not really related as you are asking.

If you have access to another camera, I would be interested in seeing if BYE behaves the same as with your camera.

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10 hours ago, djnibler said:

Thank you very much for the fast, informative, and detailed reply. 

So a couple follow-up questions - I always have the aperture setting option in BYE - even when I have my camera connected to my telescope which has no adjustable aperture. My scope is an 8" SCT with manual focus knob. When using the imaging or focus functions of BYE, and camera set to M mode, I can always set the shutter speed and the aperture. For a given shutter speed, changing the aperture setting in BYE results in changes to the exposure of the image that is captured. My 8" SCT telescope has a focal ratio of f10 - so does this mean I should configure BYE's aperture setting to f10, and control exposure with shutter speed alone? Or should I juggle both, and if so, any guidelines for how I should prioritize between the two?

This is odd.

Try deleting the cache in BYE.  See Advance Settings.

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Ok you guys were right. What was happening was that I do all my BYE learning/testing/exploring while sitting with the camera and laptop at my desk, and I have a Canon lens attached to it just so I can see what's going on and take test shots. Then when I am out in the field, I have the telescope attached instead of Canon zoom lens. I guess I didn't notice the lack of aperture column while out in the field, but it was there during testing. 

 

Mystery solved. Thank you both again!

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