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Thread: Focusing problem with 35mm f/1.8 prime lens..

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    Focusing problem with 35mm f/1.8 prime lens..

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    Hi all,
    Have recently acquired this 35mm f/1.8 DX lens. Having played around with it last week in Genting and i have this question to ask here...

    How can i focus 2 persons the same time sharply in M mode while throwing the background into out-of-focus? I have no problem focusing sharply on 1 person since the focus selector can be moved around in the frame to suit my desire, but when there's 2 persons or more in the frame, i can only choose 1 out of 2 of them to focus, so naturally the other person will not be focused.

    I have tried using f/4, f/5.6...larger number, the picture seems to come out better focused in most part, but the shutter speed has to slow down a lot which induces blur pics also.

    Is there something to do with the camera setting?

    Thx for viewing. Appreciate feedbacks.

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    like this... f/5.6 @ 1/200 with SB-600.

    how can i focus sharply these 2 persons?

    on another note, when i use f/5.6 with flashgun turned on, the shutter speed is limited at 1/200 only. why?
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    Re: Focusing problem with 35mm f/1.8 prime lens..

    built-in flash has the speed of only 1/200 mah...unless u get an external speedlight, then u can use FP-Sync and u can go up to 1/4000 oso if u want.

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    Quote Originally Posted by ahteh View Post
    built-in flash has the speed of only 1/200 mah...unless u get an external speedlight, then u can use FP-Sync and u can go up to 1/4000 oso if u want.
    does SB-600 an external speedlight? i have one attached to my camera each time when taking pics.

    What is FP-Sync? thank you

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    i think ahteh mis read your info. He though you using popup instead of SB600.

    Have you tried the auto mode? from there, you can see the setting for that scene and use that info in M mode to fine tune the final compose.

    In fact from your photos, it doesn't show blur but just the focus is on your mother thus your dad look blur. To make both subject sharp in image, try to go F9, F10 and higher.
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    Re: Focusing problem with 35mm f/1.8 prime lens..

    Quote Originally Posted by ahteh View Post
    built-in flash has the speed of only 1/200 mah...unless u get an external speedlight, then u can use FP-Sync and u can go up to 1/4000 oso if u want.
    yes but for me is FP is probably only usable in over bright back light conditions... not useful in low light.

    Read kenrockwell's write up on it.

    FP Modes (also called High Speed/FP flash synch on Canon) back to top
    Now that you know that the shutter needs to get all the way open to let the instantaneous pop of an electronic flash expose all of the film or sensor, what if instead we made the flash stay on long enough to let the curtains of a focal plane (FP) shutter complete their travel from one side to the other? We could let the flash expose the film or CCD at any shutter setting during the time it takes the curtains to travel from one side to the other.
    You can do that as a trick mode with many high-end flashes and cameras. It's called the FP mode.
    There are many disadvantages, which is why I don't ever use these modes.
    1.) FP mode often reverts to totally manual exposure calculation. If so, it's only useful for shooting things that stay at the same distance so you can calculate it. I saw this feature illustrated in a Nikon brochure, and lo and behold, the two examples were 1.) a water skier shot from the boat (the rope stays the same length) and 2.) a shot of a race car made from a camera bolted to the car and fired remotely. Some newer cameras like the D2H have automated this, finally.
    2.) The flash always pops at full power on the flashes I've seen. Thus as above you lose battery life, have long recycle times, no high frame rates and all the other disadvantages above.
    3.) Since only a fraction of the light at any time is exposing the film or CCD you lose a lot of light, again getting you back to the problems of limited flash range. The loss of light also depends on the shutter speed you use, thus the flash guide number used in manual calculations in 1.) above changes with shutter speed! You lose most of the light at the faster speeds and lose less at slower speeds.
    At least FP mode gives you the flexibility to use any shutter speed and also because you lose a lot of light you can get to the larger apertures.
    This can be a handy feature in limited applications, however there are so many limitations you see why I don't consider it anywhere as useful as a healthy true sync speed.
    Some of the very latest cameras like the Nikon digital SLRs and Minolta Maxxum/Dynax 7 have FP modes that are TTL and do vary the power down from full. This way you have only the disadvantage of 3.) above. I have not researched these; believe it or not I'm too lazy.

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    oh, dint notice ur using SB-600...my bad

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    no problem la mr ahteh...just that i m a greenhorn and wasnt sure what u were refering to..

    here's another question,

    for instance when there's foggy weather in Genting, say i want to capture a clear sharp image from corner to corner, i would use larger f stop eg. f/8..etc.

    when f/8 is used, the amount of light travel to the sensor is less, so i need to use a longer shutter speed to compensate, rite?

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    Quote Originally Posted by tom_ting View Post
    no problem la mr ahteh...just that i m a greenhorn and wasnt sure what u were refering to..

    here's another question,

    for instance when there's foggy weather in Genting, say i want to capture a clear sharp image from corner to corner, i would use larger f stop eg. f/8..etc.

    when f/8 is used, the amount of light travel to the sensor is less, so i need to use a longer shutter speed to compensate, rite?
    that is right

    the thing is, if you are close to the object that you're focussing,
    then the thinner the DOF. so i think it is better to move away from the object a little bit,
    or you should frame so that both the subjects are in the same distance from you, so they both would be in focus,
    even if you use f1.8
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    Re: Focusing problem with 35mm f/1.8 prime lens..

    many thanks Bro Bakri.

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    thanks all the senior here...i just noted my problem yesterday when taking group photo....lolx

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    Another tip:

    Try to get as much as the people to be "parallel' to the sensor plane. Even F4 can do group shots.

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    Re: Focusing problem with 35mm f/1.8 prime lens..

    That's the problem with our new crop of photographers or maybe it's an issue with the generation as a whole..

    Some just don't read, or too lazy to read or to understand a certain subject (any subject for that matter). If the teacher don't teach in school, then no need to waste time reading books or do self-research... (I'm sometimes guilty of these too..)

    While it's good to ask questions without feeling shy but it's better to invest some time into doing some research on the subject to understand it better. Once you have the basic understanding, then u can learn faster even on your own with some common sense or logical thinking..

    Photography is part science, part art. And science can be explained or understood with logical thinking. Of cos it helps if you've studied (and understood) physics. But if you studied physics without understanding the subject, then too bad (probably means u lacked common sense). then you'll need more time understanding the science behind photography and the technical aspect of it.

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