ND filter step up or step down

<p>Have 24-70mm lens with 82mm filter thread that needs a variable ND filter.<br />Seemed logical to get an 82mm sized filter that could be stepped down to the more common 77mm thread size of many other useable lenses,<br />but the general impression is that a 77mm filter might well be fine stepped up to a 24-70mm's 82mm thread with the advantage of it being cheaper<br />and just as importantly with no vignetting issues etc "cropping" up.<br />Any info on this would be appreciated.</p>

<p>Vignetting will definitely be a concert if you step down from the 82mm filter thread to a 77mm filter, especially as you get into the wide angle end of the lens. Better to go with an 82mm filter or larger, or something like the Cokin P-series filter holder for rectangular ND filtres.</p>

<p>Who said there wouldn't be vignetting issues?! If you want to share filters between lenses of different thread diameters, always size your filters for the largest diameter.</p>

<p>Sizing for the largest diameter seems the logical way to go to me too, so just checking before splashing out as there is much talk of 77mm filters and barely for 82mm which got me thinking.<br>

I guess 77mm diameter must be more a standard size for most lenses.</p>

<p>Hi Joe, you're being a little cryptic about your camera body (i.e. issues "cropping" up). Should we assume you're using a 1.6x body and are wondering if you can get away with the 77mm filter not vignetting due to the decreased field of view?</p>

<p>There are probably calculations you could do or mock-ups you could make that might approximate the situation. Worst case, you could try it out and return the items if it's a problem (and the shop has a good return policy). I'm not a pro photographer but that's my advice as an engineer.</p>

<p>Thanks Ed V, but not trying to be cryptic, just a Nikon to 5D convert trying to avoid that "Doh!" moment further down the line before paying not a little for what is a crucial bit of kit - again.<br>

Trust me - switching systems and all it entails kit-wise is painful enough without checking and double-checking what might seem to be the obvious.</p>

 

<p>Understood, Joe. I shouldn't have assumed--just asked. If you're using a 5D then the above advice from William and Sarah applies.</p>

<p>The amount of vignette (FF) is going to be to be strongly dependent on the particular lens. As well, the height of both the step-up FR adapter and the height of the filter itself are going to be critical determinants. <br>

For convenience sake, it may be worth some time to determine whether or not the additional height, decreased width, and lens's tolerances combine to make that setup usable. </p>

<p>That said, aside from the sometimes substantial additional cost, if you want a 'one for all' kit, the step ups are a usually far better idea than the step down setup.</p>