Does 2 stops of stabilisation make a huge difference between the 300mm F4L IS USM vs 400mm F5.6L US?

[thandapa2]

I'm struggling to decide between the 300mm F4L IS USM vs 400mm F5.6L USM. I've read that the 400 is sharper and obviously offers more range. Only thing putting me off is the lack of IS. I'm wondering if the two stops will be a drastic improvement compared to having no stabilisation.

[jrhoffman75]

The “rule of thumb” is that, in order to avoid motion blur from camera shake the minimum shutter speed should be 1/focal length. That would be 1/400 sec for the 400mm lens. And the 400mm lens has a maximum aperture of f/5.6. 

The 300mm lens has a 1 stop advantage in light gathering (f/4 vs f/5.6) plus IS would allow a minimum shutter speed of 1/80 second. 

But, if you need the reach of 400 vs 300 or are shooting moving subjects IS doesn’t matter. 

Don't base your decision on the presence or lack of IS. 

[p4pictures]

If you are photographing moving subjects at a distance, then often you need to use a fast shutter speed to freeze the subject motion. I know for many of my birds in flight I need 1/1000th as a minimum, and this is fast enough to hand hold either lens. 

If your chosen subjects are stationary, and a slow shutter speed will not be a problem then I am tempted to suggest having the EF 300mm f/4L IS USM and also adding the EF 1.4x Exender to give you an effective 420mm f/5.6 IS lens too. I used to use such a combination myself for many years with DSLRs.

[thandapa2]

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@thandapa2 wrote:

I'm struggling to decide between the 300mm F4L IS USM vs 400mm F5.6L USM. I've read that the 400 is sharper and obviously offers more range. Only thing putting me off is the lack of IS. I'm wondering if the two stops will be a drastic improvement compared to having no stabilisation.

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