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Some Technical (auto Focus) Help Please!  
User currently offlineCosmic From , joined Dec 1969, posts, RR:
Posted (8 years 1 month 1 week 3 days 9 hours ago) and read 4094 times:

Hi everyone.

Well, I've had my new camera for a while now (300D), and have taken it out to an Airport/Airfield about 4 times so far.

The last two times I have been quite disappointed though, this being the reason: The Camera will not AutoFocus in any of the modes Av,P,Tv apart from the basic mode (where it does everything for you), when taking photos of aircraft. It will take shots of buildings fine in all modes, but if it moves (even if slowly), it just will not focus! I am using a Canon 75-300 USM IS as the lens, and at the moment, all I can seem to use is basic mode so it AutoFocus's.

This is rather disappointing so I am seeking your advice. Is there something I am doing wrong maybe? Maybe there is a setting somewhere that needs adjusting? Could it be a fault with the camera?

Thanks for your help, as always is it appreciated lots.
Cosmic

10 replies: All unread, jump to last
 
User currently offlineDC10Tim From United Kingdom, joined Jan 2005, 1406 posts, RR: 14
Reply 1, posted (8 years 1 month 1 week 3 days 8 hours ago) and read 4086 times:

Ryan,

With the 300D you have several focus points that can be used. In fully auto, the camera will generally focus on what is nearest to it. In modes such as Av or Tv, you'll likely have it so that the centre point is used. If you are shooting an aircraft nose for example, because the fuselage is cylindrical, the lens finds it hard to fix and will zoom in and out instead of holding. This is a problem that you encounter with most lenses, although some are better than others.

I don't think there's an easy answer, other than to keep practicing. The lens you are using is very good and there are lots of excellent shots uploaded here using it. If it refuses to hold at all, have you tried adjusting it manually?

Regards,

Tim.



Obviously missing something....
User currently offlineCosmic From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 1 month 1 week 3 days 8 hours ago) and read 4082 times:

Hi Tim,

Yes, what it is doing in zooming in and out, and not holding. This goes for if it's a nose shot, side-view, head-on photo, pretty much everything if it moves.

At the moment, I am sure I have the camera on the AF mode where there are 9 points, and the camera picks the one to use. I could do with changing that to center weighted maybe? I've heard that improves things.

Tomorrow I am going to East Midlands so I will have some chance to practise then hopefully. I was at Hucknall Airfield today, and it was really frustrating that it wouldn't focus, but there wasn't that much to see, and the shots from basic mode, some are OK.

I will just have a look now at changing the AF point, and see how that goes.

Just one more thing, I have found the monitor display very deceptive, what brightness bar do you usually have it on?

Thanks Tim,
Ryan

btw, is center weighted AF this one:

-

or this one:

-
-----
-


[Edited 2006-06-18 02:45:57]

User currently offlineDC10Tim From United Kingdom, joined Jan 2005, 1406 posts, RR: 14
Reply 3, posted (8 years 1 month 1 week 3 days 8 hours ago) and read 4072 times:

Hi Ryan,

The first thread I ever started in this forum was regards the LCD screen. I thought it seemed too bright and not representitive of the actual shot. I now always keep it on the lowest brightness setting. Be sure to look at it from 90 degrees though and always check your histogram to see how the exposure is.

For focusing, generally I use the centre point, unless I'm in cirumstances where it's obvious to use one of the others (an aircraft parked at a gate in front of me for example, where I want the nose to be in focus, even if it isn't in the centre of the frame). Pages 62 and 63 in the manual tell you how to do this.

Regards,

Tim.



Obviously missing something....
User currently offlineCosmic From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 1 month 1 week 3 days 7 hours ago) and read 4067 times:

Quoting DC10Tim (Reply 3):
I thought it seemed too bright and not representitive of the actual shot. I now always keep it on the lowest brightness setting.

Yeah I noticed the same from a few photos from a while back and my last time at EMA with a few of the photos. I will change that now.

Quoting DC10Tim (Reply 3):
For focusing, generally I use the centre point, unless I'm in cirumstances where it's obvious to use one of the others (an aircraft parked at a gate in front of me for example, where I want the nose to be in focus, even if it isn't in the centre of the frame). Pages 62 and 63 in the manual tell you how to do this.

I've changed to the center point. The point it was on previously was far left! I'm glad i've discovered how to change that, it may be the reason why it won't focus. I'll get the manual out tomorrow, and have a second read through it.

The histograms on some of the photos have been looking weird sometimes, they go _||_||_. (up, down, then back up and back down). I am going to look into that aswell. That will be the exposure?

As you can see I'm asking a few questions, but i've been meaning to ask some questions for ages. The leap between the FZ5 and this is large! Lots to learn.

Thanks,
Ryan


User currently offlineJeffM From United States of America, joined May 2005, 3266 posts, RR: 52
Reply 5, posted (8 years 1 month 1 week 3 days 4 hours ago) and read 4049 times:

Quoting Cosmic (Thread starter):
I am using a Canon 75-300 USM IS as the lens,

Try a different lens. Then you will know if it's the lens, or the camera's fault.


User currently offlineCosmic From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 1 month 1 week 1 day 16 hours ago) and read 3978 times:

The camera's AF now works. It was the focus points, the Camera was focusing using a left-hand side of the view, which often was cloud. In the basic mode, I think the camera chooses the best way to focus, and so that being the reason why it worked in that mode.

Thanks for your help with that.

Just another question, in cloudy, overcast weather, how do you decide what mode to use? Yesterday at EMA I was using Av and changing the f until it was about 500/600 shutter speed. I really want a better method where I can be sure the majority of the photos will come out exposed properly, as I'm guessing a bit at the moment. What about sunny weather aswell?

Thankyou for your help,
Cosmic

[Edited 2006-06-19 18:11:35]

User currently offlinePsych From United Kingdom, joined Nov 2004, 3048 posts, RR: 58
Reply 7, posted (8 years 1 month 1 week 1 day 16 hours ago) and read 3965 times:
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Cosmic.

I think it is best to develop your understanding of the various factors that influence the photo so that you can switch between modes dependent on the situation. Generally speaking the camera will do a decent job of getting the exposure right - though of course this can get complicated in various situations.

For example, throughout most of my photography I tend to think in f-numbers, because one of the first things I think about in my photographs is depth of field. This is probably because I like a lot of landscape photography, where depth of field is a key factor in getting the result you are looking for. But in certain types of photography - aviation being an obvious example - shutter speed may be the most crucial element, to make sure you successfully freeze fast moving action.

So, aperture priority or shutter priority, is the best starting point. When you manually choose one, the camera system should fix the other variable to ensure correct exposure - whatever the weather. Another variable we now have to throw in to this melting pot is ISO - by changing this you can, for example, retain a smaller aperture in lower light and so preserve depth of field. With further experience you could look at full manual use, but for the sake of this discussion you can leave that one for now.

So - to answer your question - almost without exception I use Aperture Priority (unless it was a fast jet or I wanted blur); whatever the weather. Just get into the habit of actually looking at what the camera tells you are the settings and make sure they are within limits - nothing worse than sticking with f8 in poor light only to get a blurred shot because the shutter speed automatically set - to get the correct exposure - was too slow to freeze the movement.

Paul


User currently offlineCosmic From , joined Dec 1969, posts, RR:
Reply 8, posted (8 years 1 month 1 week 1 day 15 hours ago) and read 3958 times:

Hi Paul,

Thankyou for your detailed answer as always. It is good to hear how others' are using there cameras for aviation photography in conditions, because I can learn things from it.

On my first visit out to EMA with it, it was overcast (it is about 75% of the time with me), and I kept the aperture at f7. I regretted that, as all my shots were very dark and the Camera had automatically set itself to speeds of 1/1600. My problem really is knowing what settings, shutter and aperture to use in different situations. I don't have much confidence in the Camera if I was to say, set the speed to 1/500 on an overcast day, I would think that would be too fast and the Camera wouldn't get it right. It is hard to explain. I just want some indication from the Camera as to what aperture and shutter speed I should be using. The Panasonic had a histogram which showed you if the exposure was right, but the exposure range in what the Canon thinks is a correct exposure looks to be massive. It seems to let you do what you want, with no way of knowing if its going to come out alright.

The histograms on some of the photos look awful. I'll get some screenshots or something, but there like ______||_______.

It's not all bad though Big grin I've been impressed with the quality and lack of noise compared to my previous camera in particular. I've also had 2 accepted from EMA aswell, which I haven't had since January, which is nice.

Sorry for rambling on, but every time I go out and realise something isn't wrong, it makes me want to improve more and more.

Quoting Psych (Reply 7):
Just get into the habit of actually looking at what the camera tells you are the settings

How do you do that?

Thanks Paul,
Ryan


User currently offlinePsych From United Kingdom, joined Nov 2004, 3048 posts, RR: 58
Reply 9, posted (8 years 1 month 1 week 1 day 15 hours ago) and read 3952 times:
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Cosmic - I had a 300D too and generally was very happy with it. Just look in the viewfinder and it will tell you what the f-number/shutter speed is as you press the shutter half way down to focus/expose.

It is all too easy for your eye to look at the plane only through the viewfinder, but you can get into the habit of actually looking 'inside' the viewfinder for those figures. As I said, I favour Aperture priority - usually in the f8 - f11 range for normal shots, because this gives a good compromise between depth of field/optimum lens performance and decent shutter speed in good lighting. The problem can be that in poor light you end up with too slow a shutter speed to get the correct exposure. You can tackle this by increasing the ISO or, if you have a high quality lens, opening the aperture (without any quality loss) - though then of course you need to think more about depth of field. If you have a steady hand I don't think you always need a fast shutter - for taxiing aircraft I am often in the 1/125th area. But obviously your personal ability to hold a camera still is another factor in the melting pot.

Also - with my 300D - I tended to find that the automatic exposure often was somewhat underexposed, so another factor to play with is to purposely overexpose the camera - you can do this in 1/3rds of a stop. Just have a play with this. So, for example, in poor lighting you may overexpose by 2/3rds of a stop if the photos are generally a bit dark. Once again, I would advise you to check what the effect of that is on the shutter speed/aperture.

Cheers.

Paul

P.S. The camera will never tell you what shutter speed/aperture you should be using. All it will do is 'calculate' the correct shutter speed to get the shot exposed if you set the aperture, or vice versa if you set the shutter speed. There are a whole range of shutter speed/aperture combinations for the same situation - increase one by a 'stop' and the other will reduce by a 'stop'. You need to be thinking more about what gets you the best quality from the lens; what depth of field is right for the subject; will it be sharp/blurred etc. It's the motive that's key - no point in trying to get a panning shot if you haven't set a particular slow shutter speed; no point in wanting the background aircraft also to be in focus in a photo if you have f5.6 set just to get a fast shutter speed.

[Edited 2006-06-19 19:30:28]

User currently offlineCosmic From , joined Dec 1969, posts, RR:
Reply 10, posted (8 years 1 month 1 week 1 day 13 hours ago) and read 3934 times:

Hi Paul,

Another detailed reply, thanks it helps alot!

Reading this, it's a bit like balancing an equation. I did notice when using the Panasonic that you can use different combinations for the a similar result. I will have a go at keeping the aperture value above 8 next time I go out, and use the ISO to compensate for the shutter speed.

Quoting Psych (Reply 9):
I tended to find that the automatic exposure often was somewhat underexposed, so another factor to play with is to purposely overexpose the camera - you can do this in 1/3rds of a stop.

I've noticed this aswell, defiantly something to look into.

Quoting Psych (Reply 9):
All it will do is 'calculate' the correct shutter speed to get the shot exposed if you set the aperture, or vice versa if you set the shutter speed. There are a whole range of shutter speed/aperture combinations for the same situation - increase one by a 'stop' and the other will reduce by a 'stop'. You need to be thinking more about what gets you the best quality from the lens; what depth of field is right for the subject; will it be sharp/blurred etc. It's the motive that's key - no point in trying to get a panning shot if you haven't set a particular slow shutter speed; no point in wanting the background aircraft also to be in focus in a photo if you have f5.6 set just to get a fast shutter speed.

Thanks for telling me that, I understand what the camera does now as far as calculating exposures.

Thanks for all this help Paul, I will be able to give a more detailed reply when I've tried these different things out, and I look forward to doing so!

Thanks,
Cosmic

[Edited 2006-06-19 21:05:34]

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