DSlr talk

Davidoff · May 21, 2005

Well, I have a Dslr question right now, but I might remeber other ones in the future, if I do I'll just post them here, hold tight

:.

In burst mode, can you control de shutter speed of each of the exposures? of course, if your shooting at 3fps your shutter speed has to be as quick as or quicker than 1/3 of a second, but what if that's not enough to expose the shot? If it's enough light, can we speed it up to freeze action?

By the way my search for the lens I'll need when I finally decide to buy the xt are now has now arrived at a new place.... I'm thinking of getthing the kit lens for the wide angle and for everything else..... the tamron 28-75 2,8. I think it will be my primay lens particularly outdoors. plus for that price, weight and size I imagine I won't get better quality glass suited for my needs. My portrait fever will also be attended by this lens, post poning the 50mm 1,8.
Thanks in advance for your comments

P.S: feel free to check my frequently updated album at http://photobucket.com/albums/v714/blitzchampion/

bkriete · May 21, 2005

The shutter speed used in burst mode is whatever your camera is set at. If it's at 1/800 of a second, you will get 3 exposures per second taken at 1/800 of a second as long as you hold your finger down (until the buffer is full). You probably won't be doing many "bursts" at 1/3 of a second per exposure. Way too slow to stop action, that's more of a landscape speed when you're stopped down to get good depth of field, and you'll need a tripod for it anyway. Answer your question?

Davidoff · May 21, 2005

Perfectly, thanks .

Davidoff · May 23, 2005

Possibly dumb question..... when you say a lens focuses slowly, are we assuming they are slow when comparing to some other lenses or are you comparing them to P&S focusing speeds?

pathfinder · May 23, 2005

Davidoff wrote:

Possibly dumb question..... when you say a lens focuses slowly, are we assuming they are slow when comparing to some other lenses or are you comparing them to P&S focusing speeds?

Autofocus lenses for SLRs ( or DSLRs) tend to come in two flavors - consumer level quality and professional level quality. In the Canon brand, the better lenses tend to have USM motors in the lens for AF power. USM motors are faster and quieter than the non-USM powered lenses. The camera bodies also play a role in speed of AF also. Even the consumer grade lenses tend to be faster than the AF in P&S cameras - but that is a generalization and not always true - depends on which P&S and which lens and which body. Lots of variables to consider.

AF in a good pro SLR with a good fast lens in bright light will seem instantaneous, but as the light level drops it will be slower and slower until it fails long after the sun has set. If you get a chance, look through the viewfinder on a pro DSLR and compare it's handling wiith other cameras. It is like driving a sports car, versus a truck. Both will get you to your destination, but one is faster, more controlable, and more fun.

Davidoff · May 23, 2005

pathfinder wrote:

Autofocus lenses for SLRs ( or DSLRs) tend to come in two flavors - consumer level quality and professional level quality. In the Canon brand, the better lenses tend to have USM motors in the lens for AF power. USM motors are faster and quieter than the non-USM powered lenses. The camera bodies also play a role in speed of AF also. Even the consumer grade lenses tend to be faster than the AF in P&S cameras - but that is a generalization and not always true - depends on which P&S and which lens and which body. Lots of variables to consider.

AF in a good pro SLR with a good fast lens in bright light will seem instantaneous, but as the light level drops it will be slower and slower until it fails long after the sun has set. If you get a chance, look through the viewfinder on a pro DSLR and compare it's handling wiith other cameras. It is like driving a sports car, versus a truck. Both will get you to your destination, but one is faster, more controlable, and more fun.

Hum... ok, so a lens that isn't USM like the 50mm will probably focus slower than a USM zoom but still faster than a p&s on normal light? Another thing USM is for canon, the sigma equivalent is HSM, what about tamron?
Anyway, out of the lenses that I plan on buying anyone will focus faster thatn my old minolta p&s... in real low light it can take around a second to focus

Steve Cavigliano · May 23, 2005

Davidoff wrote:

Hum... ok, so a lens that isn't USM like the 50mm will probably focus slower than a USM zoom but still faster than a p&s on normal light? Another thing USM is for canon, the sigma equivalent is HSM, what about tamron?
Anyway, out of the lenses that I plan on buying anyone will focus faster thatn my old minolta p&s... in real low light it can take around a second to focus

David,
In my experience, a HSM lens is slower to focus than a USM lens, all things being equal. HSM is faster than non-USM and probably much faster than most non-Dslr digitals.

Low light is a toughie. In really poor lighting (like EV 2 and below) and without AF assist, it can take a second, or more, to acheive focus lock even with the best lenses. The AF is looking for contrast and if everything is black, it has a hard time and may hunt

Steve

Sheila Smart · May 23, 2005

A tip: Ensure that you are in Al Servo when shooting in continuous mode. This will retain the focus lock, whereas One Shot will not.

Here's a shot I took using this mode

http://www.pbase.com/sheila/image/42118508

For those interested how I got this shot. You take a flock of cockatoos, add sunflower and parrot seed on garage roof, take one husband with broom handle, hit underside of garage roof - it worked - but it really upset the brushtail possum who resides in a clock casing in our garage.

Cheers
Sheila

pathfinder · May 24, 2005

Davidoff wrote:

Hum... ok, so a lens that isn't USM like the 50mm will probably focus slower than a USM zoom but still faster than a p&s on normal light? Another thing USM is for canon, the sigma equivalent is HSM, what about tamron?
Anyway, out of the lenses that I plan on buying anyone will focus faster thatn my old minolta p&s... in real low light it can take around a second to focus

You are correct that HSM is Sigma's version of a faster focus motor. But a 50 f1.4 Canon lens may focus faster than a 300mm Canon with USM - shorter focal length lenses don't have to move the lens elements near as far as longer telephotos do. Not sure if Tamron markets a faster lens motor off the top of my head.

As I said earlier, as the light level drops, even the very best lenses and cameras begin to lose the ability to AF. If there is no contrast in the scene, there is nothing for the AF to lock onto. I have had to focus manually many times with my 1DMkll and an f1.4 lens when I am shooting landscapes after sundown and there are no bright lights in the scene.

Davidoff · May 24, 2005

Thanks for your replies! Can anyone explain Al servo ? Steve, don't dslr's have those autofocus assist lights? Or do I need a flash for that?

Steve Cavigliano · May 24, 2005

Davidoff wrote:

Thanks for your replies! Can anyone explain Al servo ? Steve, don't dslr's have those autofocus assist lights? Or do I need a flash for that?

David,
AI stands for Artificial Intelligence. So AI Servo uses a predictive focus algorithm. Which tries to predict where the subject will be in the succeeding frame(s). It also helps to have the focus point(s) layed on the subject in all frames. This feature comes in handy when shooting sports or motion. Like birds flying. A good example would be, taking a pic of a child swinging on a swing. If you are standing in front of the swing, the child will move in and out of focus as the swing moves. Using AI Servo you can get these shots, almost all of which will be in focus

You are right that many Dslrs have AF Assist. Most are located on the flash module itself.

Steve

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