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Old Monday 30th August 2010, 16:57   #1
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Focus Trap - fernando

Fernando, i see you mentioned using ' Focus Trap ' somewhere here in the Digi Forums.

Is this something only a Pentax DSLR owner can use ?

I believe Focus Trap is where you can keep your finger fully pressed on the shutter, and you focus at the same time, and the camera will only take the shot once focus has been achieved, is that correct ?

I had a Pentax K10D sometime ago, but i didnt fully get to grips with this method. Basically, i didnt know how to set it in the menu
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Old Tuesday 31st August 2010, 08:52   #2
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I think any brand can do it, I'm using Nikon in my case.

That's exactly that, the shutter only releases if the camera is focused. I'm still working in the same way I was for static birds, I focus and press the shutter at the moment I want, the improvement is that now that camera only fires if the image is focused, I never failed focus much but now I don't fail at all for static subjects.
For birds in flight I usually keep the focus pressed, and do my best to keep them in focus, the cameras fires every time I get the bird in focus.

There's still the chance for OOF images, I had to rethink my technique for this system, I have to slow down a bit at the focus point now, if I keep turning the focus knob after the camera fires the focus will still fail as by the time the camera releases the focus is off again.

The problem is using this with an ED80, the F/7.5 doesn't help at all here. I'm trying and ED70 F/6 for this, at F/6 the camera's AF sensors works extremelly well, any of them. With the ED80, only the central works fine, but even then it struggles in low light. Of course a better body would help here.
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Old Tuesday 31st August 2010, 12:30   #3
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So if you have your finger on the shutter button, fully pressed down while focusing, what is stopping the shutter from firing ?

When i tried this, the shutter just fired immediatley when i fully pressed it. Even though i wasnt focused properly, it still fired.

Thats the bit i do not understand. What setting inside the menu of the camera is telling the shutter not to release until focus is achieved ?
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Old Tuesday 31st August 2010, 13:04   #4
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Essentially you'll need the camera in AF mode, of course for that you'll need a chip that allows the camera to be in AF mode even without AF, dandelions do that perfectly.
With Nikon if you set it to AF-S, the camera won't fire unless the image is focused. In AF-C (continuous focusing) some bodies fire others don't, so for this is better to use it in single shot mode (AF-S). In other brand bodies I have no idea.
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Old Tuesday 31st August 2010, 13:29   #5
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OK, i see what you mean fernando.

I would only be able to use Focus Trap with the Focus Confirm chipped adapter fitted ( i have one already ) but since this only works with the scope at 600mm, ( no barlow ) then i'll try this.

I'm not sure which setting in the menu of my Canon 40D to use, so i'll have to experiment
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Old Tuesday 31st August 2010, 13:57   #6
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Googling focus trap with Canon 40d says it cant be done
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Old Tuesday 31st August 2010, 15:12   #7
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Quote:
Originally Posted by FernandoBatista View Post
Essentially you'll need the camera in AF mode, of course for that you'll need a chip that allows the camera to be in AF mode even without AF, dandelions do that perfectly.
With Nikon if you set it to AF-S, the camera won't fire unless the image is focused. In AF-C (continuous focusing) some bodies fire others don't, so for this is better to use it in single shot mode (AF-S). In other brand bodies I have no idea.
Sorry guys for barging in.

Fernando, I am using a Nikon D300s and would like to know how you did the AF thing. I have checked through the dandelion product and good thing its a company in my country. I have attached a pic showing a pink circle on the selector lever, is this the one you're saying to set at AF-S or should the setting be done in the menu section? What about other camera settings? Where should the dandelion be glue on to since I sometimes attach the camera direct to the scope and sometimes to the 1.4X TC? (See attach adapter) I am currently using.

I have been getting 1 in a 100 keeper rate after so many tries, but still I am very unwilling to give up. Hope you can provide some insight. Thanks

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Old Tuesday 31st August 2010, 16:28   #8
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Hi TBC,

The easiest way is put that switch on S (AF-S). On the D300 you also have the choice to put it in C, and set on the menu for focusing priority... but just put it in S and it will work perfectly.

On that body you'll have also the advantage to use more than the central AF point, since it has several cross points, and also any of them work better than the central of my D90's, so that's a plus for you.

You should glue the chip on the adaptor on the scope, then it will work both with the TC or without the TC. But don't get your hopes high with working with the TC, at F/10.5 the camera will have an hard time focusing on anything.

1 on 100 is way too low...why are you getting a so bad rate? bad eyesight? missaligned mirror?
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Old Tuesday 31st August 2010, 19:33   #9
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Good info for Pentax / Samsung camera's. Just need to try it myself now...

http://www.pentaxforums.com/forums/p...tch-focus.html
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Old Tuesday 31st August 2010, 20:03   #10
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Looks like my Canon 450D will do focus trap and will also do it in Live View.

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Old Tuesday 31st August 2010, 20:30   #11
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Paul, what would you set in the menu ?

I'm thinking the 450D + 40D might not be too far apart in the menus ? Maybe i could try this Focus trap thingymajig
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Old Tuesday 31st August 2010, 21:52   #12
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I've copied and pasted below what I read on the DP Review forum. It involves going into the 450D custom function menu so I don't know if this is similar to the 40D.

Set up the camera with C.Fn-10 to 0 (focussing is triggered by the shutter), One-Shot AF mode, single focus point, and the lens set to AF.


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Old Tuesday 31st August 2010, 21:58   #13
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What exactly is Custom Function 10 on your camera ? I only have 9 but it maybe that its in a different position, but i need to know what it is.

1 shot + single point focus is no trouble, but setting a MF lens to AF.. How do you do that
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Old Tuesday 31st August 2010, 22:05   #14
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Ah, i think function 10 on your 450D is AF/AE lock ?

Trying to find that on the 40D
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Old Tuesday 31st August 2010, 22:10   #15
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Quote:
Originally Posted by Musoman View Post
but setting a MF lens to AF.. How do you do that
That's what the dandelion does, dandelion comes with default programing as an AF lens, it can be change to MF if needed but AF is the default.
In "nikon language" it works like any G lens, it fools the camera into thinking there's a G type lens with a built in motor, but not having a motor on the lens obviously it doesn't move. Yet the camera thinks the lens it's doing it job and releases the shutter only when focused.
I don't how canon works but it should be more or less the same.
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Old Tuesday 31st August 2010, 22:20   #16
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Ah, i think function 10 on your 450D is AF/AE lock ?

Trying to find that on the 40D
Yeah, it's the AE lock, AF lock. I can't try it out on my scope as I haven't got round to getting the focus confirm chip off ebay. Shall have to get one.

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Old Tuesday 31st August 2010, 22:28   #17
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There's no custom function on the 40D for ' AF/AE lock '

Does the adapter have to be a ' Dandelion Chip ' ? I've never heard of Dandelions, just regular Focus Confirm adapters like i already have.

Mind you, this is all academic now, as this crucial custom function is missing on my cam
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Old Wednesday 1st September 2010, 10:45   #18
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Oh, I know nuts about Canon or Nikon. On my old Sony A350, I can set my shutter release priority to release or focus. Meaning if set to release, the shutter will release regardless of focus. But if set to focus, it will not release until the focus is spot on. But I can't find that on my A550 now??????

I belief that function works on AF lenses (while in MF mode) as well as MF lenses with the Dandelion Chip.
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Old Wednesday 1st September 2010, 14:55   #19
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Hi TBC,

The easiest way is put that switch on S (AF-S). On the D300 you also have the choice to put it in C, and set on the menu for focusing priority... but just put it in S and it will work perfectly.

On that body you'll have also the advantage to use more than the central AF point, since it has several cross points, and also any of them work better than the central of my D90's, so that's a plus for you.

You should glue the chip on the adaptor on the scope, then it will work both with the TC or without the TC. But don't get your hopes high with working with the TC, at F/10.5 the camera will have an hard time focusing on anything.

1 on 100 is way too low...why are you getting a so bad rate? bad eyesight? missaligned mirror?

Hi Musoman, Sorry for asking question in your thread. Let me know if it does bother you, I'll open a new one.

Hi Fernando, thanks for the reply. I'll order the chip ASAP. I am not sure of the low keeper rate as well because I am new to DSLR, don't know if the techniques are wrong / wrong settings / bad eyesight or a combination of all.

Mind to elaborate more on misaligned mirror? How do I know and how to check? Mirror in the DSLR? I thought they are just there to reflect to images to the viewfinder?



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Old Wednesday 1st September 2010, 15:32   #20
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I don't think there's any technique involved except having decent eyesight. With time the eye gets "educated" to see the needed details to distinguish what is or not focused, but still even in the beginning anyone with a good eyesight should have a better keepers rate than that.

The mirror you see when you take the lens of your camera is the mirror that reflects the image to the viewfinder and that's the mirror that can be misaligned.
So, behind that mirror there's a eccentric bolt (two actually, but the other is for the AF sensors, forget the other, you only need the first for this), that bolt aligns the mirror so the image it reflects is aligned at the same plane of the sensor.
The easiest way to check it is to get the fastest lens you have, preferably one that focus very close, a macro lens is about perfect. Put your camera on a solid tripod, get a ruler, focus manually on any number, keep the lens wide open, put the line referring to the number at the exact centre of DOF on the viewfinder, if the mirror is misaligned the resulting image will have that dof decentered from the line you focused on. If that's the case you'll need to either send the camera to nikon, or mess with that bolt until it's right. I'm a DIY guy so you know my choice

Here's a link that explains all this better:
http://www.leongoodman.com/d70focus.html

The article refers more to the AF part, but the process is nearly the same.
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Old Thursday 2nd September 2010, 00:13   #21
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The Dandelion chip also has the ability to be programmed to adjust the focus confirm point, so you don't have to tinker with the AF eccentric bolt (which would affect the AF point for all lenses). I find the "green dot" confirm gives better results (more repeatable) than my eyeball for manual focus lenses ...
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Old Thursday 2nd September 2010, 09:48   #22
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I didnt realise that they had the name ' Dandelion '

I've got 2 of these adapters for a couple of my DSLR lenses, and yes, i prgrammed them to the lens they fitted, and you get EXIF data, and the ability to correct front or back focus.
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Old Thursday 2nd September 2010, 09:50   #23
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If i'm understanding you correctly, there is a menu function in my some cameras to "offset" the auto focus instead of having to alter the mirror manually.

http://stanfordphoto.blogspot.com/20...autofocus.html

Sorry if this isn't what you are talking about...


Quote:
The mirror you see when you take the lens of your camera is the mirror that reflects the image to the viewfinder and that's the mirror that can be misaligned.
So, behind that mirror there's a eccentric bolt (two actually, but the other is for the AF sensors, forget the other, you only need the first for this), that bolt aligns the mirror so the image it reflects is aligned at the same plane of the sensor.
The easiest way to check it is to get the fastest lens you have, preferably one that focus very close, a macro lens is about perfect. Put your camera on a solid tripod, get a ruler, focus manually on any number, keep the lens wide open, put the line referring to the number at the exact centre of DOF on the viewfinder, if the mirror is misaligned the resulting image will have that dof decentered from the line you focused on. If that's the case you'll need to either send the camera to nikon, or mess with that bolt until it's right. I'm a DIY guy so you know my choice
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Old Thursday 2nd September 2010, 10:21   #24
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That’s AF, that will not align what you see in the viewfinder. It is useful to adjust the AF too when using focus trap, as that is dependent of AF accuracy. But the viewfinder must be correctly aligned nonetheless, and the only way to that is with the bolt or shimming the focus screen.

Also not all cameras allows the AF adjust, luckily as said by the others, Dandelion chip allows that adjustment in the programming mode.
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Old Thursday 2nd September 2010, 15:47   #25
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I don't think there's any technique involved except having decent eyesight. With time the eye gets "educated" to see the needed details to distinguish what is or not focused, but still even in the beginning anyone with a good eyesight should have a better keepers rate than that.

The mirror you see when you take the lens of your camera is the mirror that reflects the image to the viewfinder and that's the mirror that can be misaligned.
So, behind that mirror there's a eccentric bolt (two actually, but the other is for the AF sensors, forget the other, you only need the first for this), that bolt aligns the mirror so the image it reflects is aligned at the same plane of the sensor.
The easiest way to check it is to get the fastest lens you have, preferably one that focus very close, a macro lens is about perfect. Put your camera on a solid tripod, get a ruler, focus manually on any number, keep the lens wide open, put the line referring to the number at the exact centre of DOF on the viewfinder, if the mirror is misaligned the resulting image will have that dof decentered from the line you focused on. If that's the case you'll need to either send the camera to nikon, or mess with that bolt until it's right. I'm a DIY guy so you know my choice

Here's a link that explains all this better:
http://www.leongoodman.com/d70focus.html

The article refers more to the AF part, but the process is nearly the same.
Thanks Fernando,

The link you provided was very informative. I'll try it over the weekend, too bad I had only a 18-200mm f3.5/5.6 lens but I'll give it a try first.
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