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Thread: Focus and Aperture issues on a cloudy day

  1. #1
    dubeni's Avatar
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    Focus and Aperture issues on a cloudy day

    Hello
    This are my first questions here
    The camera used is a Canon 400D/XTi with the kit lens EF-S 18-55mm f/3.5-5.6 IS

    1- I find it very hard to trust auto-focus on a cloudy day and using manual focus is even harder, I've the viewfinder adjusted to my right eye, and I need eyeglasses to see up close. Here are two examples of what I mean:
    I want to capture the reflection of the fortress and sky.
    Focus and Aperture issues on a cloudy day
    Tv: 1/1600
    Av: 3.5
    ISO: 100
    Fl: 18.0mm
    Focus and Aperture issues on a cloudy day
    this one is obviously out of focus
    Tv: 1/2000
    Av: 3.5
    ISO: 100
    Fl: 18.0mm
    I'm sure you will have some nice tips on how to overcome these difficulties.
    I've seen some focus screens with split image range finder, will they work with auto-focus lenses in manual mode?

    2- Auto-focus lenses don't have an aperture ring, how do I manage aperture?

    Note: these images were cropped from 3x2 to 4x3, retaining most of the with.

    As you can see I'm a beginner with manual mode on DSLR's, I more familiar with my 35mm Nikon FM2 with a Nikor 35-70mm zoom lens.

    sincerely
    Bernardo

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    Moderator Dave Humphries's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    I can't help with the Canon 400D/XTi operation, being a Nikon DSLR shooter.

    But I have to ask
    a) whether you were in single focus point mode (that may not be Canon terminology) and
    b) was the focus point in use on the fortress?

    i.e. did you half depress to AF on the fortress, then re-compose to the view I see here?

    If you have the camera's manual, it might be wise to look up AF functions in it.
    If you don't have it, someone may be able to post a link to it online.

    Welcome to the CiC forums from ....

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    dubeni's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    Hello Dave Humphries

    I was using manual focus trying to achieve a better focus
    I just look trough the viewfinder and try to achieve the sharpest image, which is easy at close range, but at this distance and focal range (18mm) on a cloudy day it gets more difficult to distinguish the small details.
    And yes I have the camera's manual and I've read it quite a few times

    Bernardo

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    Re: Focus and Aperture issues on a cloudy day

    Hello, Bernardo. I think your aperture is too big for you to achieve a good depth of field. You can set it to f/11 or f/16 to get more focus on your shots. Some photographers have a technique when it comes to this kind of situation - once they know their composition on the frame, they look at the 1/3 spot on the lower part of the viewfinder and focus the lens on that area. That would set their hyperfocal distance using a smaller aperture opening. It won't harm you to try if it would work for you. Based on your EXIF data, I don't see any advantage on setting your shutter speed that high. You can set your aperture at f/11 and still have a decent 1/200 second shutter speed at ISO 100.

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    Re: Focus and Aperture issues on a cloudy day

    Quote Originally Posted by dubeni View Post
    Auto-focus lenses don't have an aperture ring, how do I manage aperture?
    Like Jiro mentions, shooting at f/3.5 is not recommended for this kind of a shot; both because of the very limited depth of field that aperture allows and the fact that the kit lenses do not provide their best image quality when shot wide open.

    To change the aperture, set the mode dial on AV (aperture priority) and rotate the main dial. However, always make sure that your shutter speed is at least 1/f-stop x 1.6. You occasionally may need to boost the ISO in order to keep the shutter speed that fast. But shooting at 18mm, your shutter speed needs only to be 1/30 second or faster. No problem in virtually any daylight and you would have had plenty of shutter speed in the light conditions under which you shot the first image.

    I skipped an entire generation of Canon cameras, the auto-focus film cameras, because I thought that I could focus manually faster and more accurately than the camera could auto focus. I was dead wrong and now almost always autofocus, except when shooting macros. My old eyes "ain't what they used to be" as the song goes and I need auto focus even more than I did ten years ago.

    There should be absolutely NO PROBLEM autofocusing in virtually any daylight. Using 18mm at f/11, your depth of field would be 3.3 feet to infinity if the camera was focused at 6 feet. It is difficult to get anything OOF with a DOF that deep!

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    Re: Focus and Aperture issues on a cloudy day

    Hi, as I sit here playing with my 400D I can understand your problem. What Richard & Jiro mentioned is solid information. As you are focusing, looking through the viewfinder, with manual focusing, do you half press the shutter button? If so, you should have a beep & a red dot appear in the viewfinder when correct focus is achieved. The sweet spot for you lens, aperture wise that is, is going to be in the area of F-9 .5 - 13. At least it is on the 28x135 lens I have on the XTI. Try that same shot, maybe on a tripod, mirror lock up ( custom function #7) with timer set. Let's see that shot again with some of these suggestions. Well, back to studying my 7D.

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    dubeni's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    Thank you Jiro, Richard and Mike.
    I'm sure you are right, I have to try a higher f number and maybe the shutter speed want matter so much.
    This is a tricky shot because it can only be taken on a low tide when the wave goes out and with a relatively calm sea.
    If you add a cloudy or almost stormy day (no rain please ) I end up with a few days available in a year.

    Some photographers have a technique when it comes to this kind of situation - once they know their composition on the frame, they look at the 1/3 spot on the lower part of the viewfinder and focus the lens on that area. That would set their hyperfocal distance using a smaller aperture opening.
    You understood exactly what I want, it took me quite a few hundreds of shots from different locations (yippee for DSLR's) to decide what I wanted to frame on this vast beach landscape. I've been going there for at least 50 years and I've seen it at all hours, that's why I decided for a cloudy uneven grey sky.
    90% of the times I go there are sunny days , the other 10% are warm summer nights .
    This is a personal project, an enlarged photo to have at home, so I'm not in a rush, I will share the final version, it may take a while...

    To change the aperture, set the mode dial on AV (aperture priority) and rotate the main dial. However, always make sure that your shutter speed is at least 1/f-stop x 1.6.
    I used the aperture priority mode (AE) wide open with a high shutter speed because I thought that the reflection of the fortress would come out better due to ripples on the water caused by a slight breeze.
    I usually set the shutter speed 1/f- stop more or less, I find it easier to correct an under exposed picture. What does the x 1.6 mean? what do you mean by OOF?

    As you are focusing, looking through the viewfinder, with manual focusing, do you half press the shutter button? If so, you should have a beep & a red dot appear in the viewfinder when correct focus is achieved.
    I think so, but never noticed the red dot, or maybe I did but didn't pay so much attention. I will be alert next time.
    I do use mirror lock up and a remote shutter release for shots of the moon on my telescope, never thought of it for daylight exposures. It is going to be an interesting experiment

    Thank you

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    Re: Focus and Aperture issues on a cloudy day

    Hi Bernardo, if you post something that you want removed, such as a double post, you should be able to remove your own post by clicking on Edit Post at the bottom.

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    Re: Focus and Aperture issues on a cloudy day

    Thank you
    Done

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    Re: Focus and Aperture issues on a cloudy day

    I probably wont be able to explain this as well as Richard but the 1.6 is because you are using a crop factor camera. When you look through a 50mm lens the image will actually be as if you were using an 80mm lens because it is projecting the image on a less than full sized sensor. So some formulas that were created for full frame cameras have to be adjusted for crop factor cameras by adding x1.6. The acronym OOF is for out of focus.

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    dubeni's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    Ok
    Thanks Paul, I know what you are talking about, I misunderstood the meaning of it in the context of the phrase.
    OOF lol, out of focus, ok.

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    Re: Focus and Aperture issues on a cloudy day

    The reason for needing the faster shutter speed on a 1.6x camera is basically that the image needs to be enlarged to a greater degree than an image from a larger format such as a full frame camera. Therefore, the image needs to be a bit sharper and thus there is less tolerance for camera movement. A faster shutter speed will stop any camera motion better than a slower speed. Of course, IS compensation allows you to use a slower speed.

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    Moderator Dave Humphries's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    Quote Originally Posted by dubeni View Post
    Hello Dave Humphries

    I was using manual focus trying to achieve a better focus
    I just look trough the viewfinder and try to achieve the sharpest image, which is easy at close range, but at this distance and focal range (18mm) on a cloudy day it gets more difficult to distinguish the small details.
    And yes I have the camera's manual and I've read it quite a few times

    Bernardo
    Hi Bernardo,

    Oh dear, I hope I didn't sound patronising no offence intended

    Now, from the later replies above, I understand more what you are after.

    Manual focusing on a DSLR is only really possible using Live View (which I don't think the 400D has) and without the old split prism in the middle and granular ring of old film days, we are reliant on AF these days.

    Willie (jiro) and Richard have answered other aspects of the question perfectly well, but one thing I was asking, which I don't think has been covered; If the 400D has more than one focus point, have you got the AF in such a mode that it only uses one of these - the one you choose?

    If not, it may be trying to use any or all of them as it sees fit and may make your results unpredictable.

    Hope that helps,

  14. #14
    dubeni's Avatar
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    Re: Focus and Aperture issues on a cloudy day

    Quote Originally Posted by Dave Humphries View Post
    Hi Bernardo,

    Oh dear, I hope I didn't sound patronising no offence intended

    Now, from the later replies above, I understand more what you are after.

    Manual focusing on a DSLR is only really possible using Live View (which I don't think the 400D has) and without the old split prism in the middle and granular ring of old film days, we are reliant on AF these days.

    Willie (jiro) and Richard have answered other aspects of the question perfectly well, but one thing I was asking, which I don't think has been covered; If the 400D has more than one focus point, have you got the AF in such a mode that it only uses one of these - the one you choose?

    If not, it may be trying to use any or all of them as it sees fit and may make your results unpredictable.

    Hope that helps,
    You don't sound patronizing at all, so no offence taken

    You are right, the 400D doesn't have live view.
    It has 9 focus points in a diamond shape with a cross-type sensor in the center.
    And yes, it has the ability to choose one of the focus points.
    In fact I've noticed that when shooting on AF mode it uses multiple points, from one trough as much as seven.

    From what I understand this points measure contrast between pixels to determine focus, being the cross type more accurate. Correct me if I'm wrong.

    With a constantly moving foreground and horizon (the waves rise above horizon) every time I focus it chooses different points, being this one of the reasons I decided to go manual. Don't forget the weather a grey cloudy day reduces color contrast.

    You guys already gave me some great tips on how to improve this shot.
    Since I found this site and forum I've been reading a lot and regaining interest in using better DSLR's.

    I guess I have to trust more the AF and learn how to use it properly.

    As for using manual focus through the viewfinder usually gives a lot of fun doing close shots like this one:

    Focus and Aperture issues on a cloudy day
    Tv: 1/500
    Av: 7.1
    ISO: 100
    Lens: 18.0 - 55.0mm
    FL: 55.0mm

    Here a full scale detail:

    Focus and Aperture issues on a cloudy day
    Quite sharp

    Sincerely
    Bernardo

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