Shutter speed rule of thumb?

[andyjayh]

Just bought myself a Sigma 2x tc to use with my 120-300. As this is the first time I have played with 600mm I was wondering if there was a RoT for focal length and shutter speed?

 

[troutfisher]

Its generally thought to be

1/focal-length*crop factor*TC factor?

totally unscientific but seems to work from the reports I read..
Cheers

 

[Roy C]

Crop factor * 1/FL is a good starting point but there are other considerations like:
Are you using any support or just hand holding ?
Does the lens have image stabilisation ?
How good the individual is at holding steady ?
How far you are away from your subject ? (in my experience with birds, the further you are away from the bird then the greater the need for goods support or a faster shutter speed).

I find with my Canon 300/2.8 + 2x tc that I can hand hold at around 1/800 sec and get sharp shots most times but that is with a 2-3 stop I.S. switched on - without the I.S. I would be looking for 1/1600 or even faster !. I am not saying that you could not get sharp shots with slower speeds but to get consistently sharp shots hand held then this is what I would be looking for.

Of course, with a good tripod and head you can get away with much slower shutter speeds.

Just my 2p's worth.

 

[HoppyUK]

Its generally thought to be

1/focal-length*crop factor*TC factor?

totally unscientific but seems to work from the reports I read..
Cheers

Yes that's right. It is actually quite scientific, but very rough and ready because everybody is different. It depends how steady you are, how you are standing, and big lenses like the Sigma 120-300 are pretty damn heavy. Up to a point, bigger lenses make thing easier because you've got plenty to get hold of and a bit of weight dampens vibration but nobody can hand-hold one of those reliably for long.

So at an effective 600mm, with the 7D's 1.6x crop factor, your're at 1/960sec minimum. Plus is you crop the image further in post processing, that also impacts on the rule, as you are enlarging the movement blur along with everything else. If you were to enlarge half the frame, that's a further 1.4x crop factor (square root of 2) and puts you up to 1/1344sec minimum.

Without image stabilisation, it's no wonder lenses like that are almost always used on a monopod. And even with IS, monopods are very good for taking the weight. Also, another good way of getting sharper results when you're on the limit is to shoot several of frames - greatly increases your chances.

Edit: crossed post with Roy

 

[Roy C]

Further to my earlier post, when using the Canon 300/2.8 with a 1.4 tc I often hand hold but when using a 2x tc I much prefer to use a good tripod and Gimbal head - probably because of a point that Richard (HoppyUK) touch on in that I often find myself having to crop fairly heavily and for that you need a pin sharp image to start with.

 

[andyjayh]

Thanks guys for the advice and help. I thought there had to be a way of roughly working out a minimum so i would know where the danger point would come in.

Unfortunately this lens does not have IS so I am not able to benefit from that tech. I mainly hand hold the 120-300 but it is hard work especially at air shows! Today I took some shots o a local cricket match and again I hand held but whilst sitting so was able to use my knee for support. Stupidly I had my monopod on the floor next to me!

However this has helped me with understanding why some shots are not sharp and I need to up the light levels to get the shutter speed I'm after. Big problem I have is one of my topics is aero modelling and most of these planes are prop driven and therefore shutter speed needs to be sub 800 for motion. No chance of hand held with this combo then.