28-135 IS question regarding IS/focal/shutter

[hugodrax]

without IS it is said shooting 200mm would require 1/250th shutter speed for safe blurfree shots.

with IS active at 200mm what is the safest shutter speed before risk of softness/blur.


1.6multiplier

[Longwatcher]

Not that the 28-135 will go to 200mm...

My experience with the 28-135 is that I can go to 1/60 against still objects with IS versus 1/125 without, based on my handholding ability.

However, when shooting other people who tend to move also, even with IS I shoot 1/125 or faster.

I seem to get a bit better response with my 100-400 IS in mode 1 when handheld, but it could be the amount of money I spent affecting my judgement here.

[hugodrax]

I was counting the cropfactor Im not sure if that matters in the shutter speed calculation for safe speeds. so 1/60th is okay at 135 with IS on?

[Longwatcher]

Against a non-moving target yes should work for most people.

At least for me. I know a few people that can hold rock steady - not me. On the other hand I also know a few people that I would never let stand behind me with any firearm, as their hands moves quite a bit involuntarily, for those IS won't help a bit ;-).

[Trivia: my thoughts go to a seargent I knew in the USAF who they gave a shotgun waiver to, because he had to be able to carry a weapon, but could not hit anything except the post in front of him, the roof, and the backstop (sometimes) with an M-16 or .38 - needless to say, it was commonly agreed that he went in front if we had to carry weapons. I figure he takes pictures at 1/3000 just to stop the motion of his hand]

[Roger_Cavanagh]

The rule of thumb for minimum handheld shutter speed on 35mm SLRs is the inverse of the focal length, so a 200 mm lens gives 1/200 sec. However, you DO need to take the smaller sensor size of the 10D, D30/60 into consideration, so the formula should be adjusted to be:

1 / (FL x 1.6):

For 200mm: 1 / (200 x 1.6) = 1/320 sec

For 400mm: 1/640 sec

The IS on the 100-400 is supposed to be worth two stops, which would reduce this to 1/160 sec. The new IS on the 70-200 Canon claim is good for 3 stops, so this would come down to 1/80 sec.

For 135 mm the min speed comes to 1/216 sec without IS - so 1/200 or 1/250 would be the setting. With IS you'd get 2 stops benefits, so call it 1/60 sec

Regards,

[Longwatcher]

Roger,
I don't think that the crop factor should be used. But I am only basing it on my experience.

I would think that the formula corresponds to arc/degree of movements per second and since you are only cropping the field of view, it should not change the formula from the base focal length.

The objects in the scene are still moving the same amount of degrees of arc caused by handshaking, we are just not seeing the same field of view.

Just my opinion.

BTW: Thanks for the formula. I now remember being told this same thing over twenty years ago, when I last was doing photography regularly.

[Roger_Cavanagh]

Tim,

I think the 1.6 is relevant here for same reason it is relevant in DOF calculations. The smaller sensor size means a smaller Circle of Confusion.

I tried to find an explanation for the 1 over focal length rule thumb, but couldn't. So I reasoned as you have that it must be to do with the amount of movement: if you keep the shakes smaller than the CoC, they won't be noticed. So since the 10D, D30/60 all have a smaller sensor, they have smaller CoC's, therefore, you have to shake less, therefore, the rule of thumb must be modified.

That's my reasoning for which I can offer no supporting references. The CoC and DOF stuff is all standard material.

Of course, CoC calculations are all based on looking at 10 x 8 from 15 inches or something, not looking at 33.5x enlargement on your PC monitor from about 6 inches. :)

Regards,

[hugodrax]

thanks very informative it would be nice if a DSLR FAQ existed this information would be good to have it in it.

[Longwatcher]

Roger_Cavanagh wrote:
Tim,

So since the 10D, D30/60 all have a smaller sensor, they have smaller CoC's, therefore, you have to shake less, therefore, the rule of thumb must be modified.


I can buy that.

However, my experience is closer to base focal length, then modified focal length. Maybe my hand is steadier then I think it is. I don't have a full frame sensor to try it on.

Short of an expensive machine, how would you test it objectively anyway.

Again thanks,

[Roger_Cavanagh]

hugodrax wrote:
thanks very informative it would be nice if a DSLR FAQ existed this information would be good to have it in it.



Hugo,

I shall make a note to add this to the stuff on my site. :)Unfortunately, my ISP "upgraded" my site at the weekend and I am still unable to publish anything new.

Regards,

[hugodrax]

I have shot some portraits of my wife at ISO 200 and a shutter speed of 1/8th of a second (ambient light) 30mm focal length (effective 48mm) And they are amazing. I would blur a picture shooting 1/8th without IS. funny thing is one of the shot she was sitting with our dog on her lap and you see everything nice and the dogs head has motion blur as he moved.

If I try to shoot 1/8th on the sony S-86