With ND400 50D fails to determine proper exposure time

<p>Hi All,<br>

Very recently I bought a Hoya 400ND filter. But, my 50D (with Tamron 18-270) exposure meter is not working. So every time, I take a photo with the filter on, I have to take one without it and then calculate the necessary f-sops reqd with the filter on.<br>

Is there any trick I should know?<br>

Thanks,<br>

Anirban</p>

<p>ND and grads are easier to use with a Cokin mount so you can quickly meter and slide the filter in.</p>

<p>That doesn't suprise me. ND400 is a 9-stop filter. The built in meter goes down only to 1EV at ISO100. You're probably 2 stops below that in bright sun.</p>

<p><Chas><br /></p>

<p>Good gosh, man! What are you photographing, sunspots? Seriously, I'm guessing you are doing long exposures in daylight conditions? I can't think of any other way with that filter than what you are currently doing.</p>

<p>Hi Charles, I couldn't catch your argument. Let's say I am in A-Priority mode. So, choosing a f/16 should calculate 20/30 sec at ISO 100 (even in bright sunlight). <br>

"The built in meter goes down only to 1EV at ISO100" - what does it mean?<br>

And Mark, yes I want to phtograph long exposures in bright daylight. that's the idea.<br>

Anirban</p>

<blockquote>

<p>"The built in meter goes down only to 1EV at ISO100" - what does it mean?</p>

</blockquote>

<p>Light meter sensitivity is expressed as a range of values, typically -1 EV to 18 EV. If you exceed that range it does not function correctly. To put it simply: your filter is so dark there is not enough light for the meter to work. </p>

<p>hmm .. sounds bad Everytime I have to unscrew the filter, focus and meter and then screw .. adjust for the 9 stops and then click the shutter.<br>

I'll accept it for the moment. Hope this yields some good shots.</p><div></div>

<p>Even a cheap handheld meter would be preferable, if one could learn to multiply by 512 in their head.</p>

<p>Although it's possible to temporarily switch ISO to 1600 or 3200, meter and go back to ISO 100 increasing exposure time 4 or 5 times it won't always work. In my short experience with 9-stop filter correct exposure with the filter was not always 9 stops longer than without filter, but sometimes it was 10 stops and sometimes 8 stops. Perhaps it depends on the spectrum of the scene since many ND filters are not truely ND (the one I used warmed up scenes slightly) and therefore exposure affected differently for different colors.</p>

<p>Besides metering problems, you still have to focus somehow and with 9-stop filter it's usually not feasible. So take filter off, focus/meter, put it back on, then shoot. Takes longer, but then your exposure time is long anyway :-)</p>

<p>That's exactly what I'm doing. It takes a lot of time, but a little practice will make it worth it!</p>