How to focus with a 10 stop ND filter ?

[bnnrcn]

What is the best way for focusing with a 10 stop ND? Do I have to focus manually before screwing in the ND or do I have to focus automatically and then turn the switch on the lens to manual focus before screwing in the ND. I used my ND filter just a couple of times with auto focus in winter time but I read somewhere that it is better not to use auto focus function because ND in front of the lens might cause wrong focusing . So I'm a bit confused about how and when (before screwing in or after screwing in the ND) to focus properly ?

Because it is summer time now, I want to try some long exposure sunset shots , that's why your comments will be really good help for me. Thanks in advance

[John 2]

Hi Binnur. To a degree, it depends on the camera. If you are using a DSLR, pre focussing is probably the only way but unless you are after extreme DOF i.e. wanting something in the immediate FG to be in focus. For sunset shots, that shouldn't be a problem because you just set the focus to infinity. If you are using a mirrorless camera or if your DSLR has a "Real View" capability, then the camera might gain up enough for you to see the image with the filter in place. In bright light on the other hand, I find that I can see sufficient detail on my D7100 anyway.

[JR1]

errr pre focus then add it

[Colin Southern]

With long-exposure sunsets generally you'll have the aperture stopped down (F16 -> F22 etc), so focussing isn't hyper-critical. In these situations I generally use a Vari-ND filter so I can AF at minimum attenuation and then increase the attenuation from there, but even then, past a certain point the camera won't AF reliably. What I do at that point is focus while there is sufficient light - switch the camera to MF - and then reverse the lens hood (for 24-70 and 70-200 lenses) (waste of time with the 16-35) so that it covers the focusing ring (if you're shooting a sunset then you'll probably be shooting into the light so a lens hood won't do anything useful anyway unless there are other off-axis light sources like car headlights and/or street lights).

The above should work well for you too; get it focussed - switch to MF - add your 10 Stop ND - and go from there. You'll probably also need a manual release so you can use bulb mode too.

[NigelD]

Live view if the exposure time permits.

[bnnrcn]

Thank you everybody for your comments

Colin, I already have a manual release, so no problem with the bulb mode.

[Colin Southern]

Thank you everybody for your comments

Colin, I already have a manual release, so no problem with the bulb mode.

No worries. Hope your binary math is good - you're going to need it with sunset shots and 10 stops of attenuation (remember too that the light also changes DURING the exposure, so often you need to add even more time).

[bnnrcn]

Do you have an approximate formula for how long I have to add for changing light Colin ? With a 10 stop ND I just multiply the shutter speed given by my camera (in AV mode) without ND by 1024 to calculate the time necessary for the long exposure. But I haven't thought of the changing light conditions actually

( If you multiply 2 by itself for ten times = 1024)

No worries. Hope your binary math is good - you're going to need it with sunset shots and 10 stops of attenuation (remember too that the light also changes DURING the exposure, so often you need to add even more time).

[Colin Southern]

Do you have an approximate formula for how long I have to add for changing light Colin ? With a 10 stop ND I just multiply the shutter speed given by my camera without ND by 1024 to calculate the time necessary for the long exposure. But I haven't thought of the changing light conditions actually

It's really just a judgement thing, and it's going to depend on how long your exposure is and how low the sun is. It's actually not as critical as you might first think because if an ideal exposure is, say, 10 minutes then anything from 5 to 20 minutes is only +/- 1 stop, which isn't a lot.

As a rule of thumb, just switch on the blinkies and see where you get them -- you'll get a feel for it after a while, especially as the exposures change from shot to shot. The other rule of thumb is "don't packup and go home until it's too dark to see your gear". It was so dark for this shot that I had to restart it after I tripped over a tripod leg wandering around waiting for the exposure to finish (12 min shot).



And this one was 40 minutes (I sat in the car reading a Kindle book!)

[bnnrcn]

I tried my ND filter on a cloudy afternoon in winter time and it actually didn't take me more than 3 minutes . So a 40 minute exposure is really long for me I will see what happens . I will keep your words in mind , thanks again

It's really just a judgement thing, and it's going to depend on how long your exposure is and how low the sun is. It's actually not as critical as you might first think because if an ideal exposure is, say, 10 minutes then anything from 5 to 20 minutes is only +/- 1 stop, which isn't a lot.

As a rule of thumb, just switch on the blinkies and see where you get them -- you'll get a feel for it after a while, especially as the exposures change from shot to shot. The other rule of thumb is "don't packup and go home until it's too dark to see your gear". It was so dark for this shot that I had to restart it after I tripped over a tripod leg wandering around waiting for the exposure to finish (12 min shot).



And this one was 40 minutes (I sat in the car reading a Kindle book!)

[John 2]

Binnur, I found this helpful.

http://digital-photography-school.co...sunset-images/

I also keep a copy of this chart in my camera bag:

http://500px.com/DustinMcGrew/storie...nversion-chart

[bnnrcn]

Thank you John, very useful link indeed Unfortunately I don't have any GND filters yet, so I will have to do some more PP untill I buy some

Binnur, I found this helpful.

http://digital-photography-school.co...sunset-images/

I also keep a copy of this chart in my camera bag:

http://500px.com/DustinMcGrew/storie...nversion-chart

[Polar01]

Binnur you talked about extra time in your post #8, there is no real formula to figure out the extra time needed. In Colin's post he stated that it was a 40 minute exposure, lets just say that the original time he worked out was 20 minutes, as the sun was going down he decided to add 1-stop more of time, well at 20 minutes 1 extra stop you make that 40 minutes now. Remember when making long exposures in the time frame of minutes, it can really be hard to over expose as to get just one extra stop you have to double the time.

Cheers: Allan

[bnnrcn]

Thank you Allan, I think I will get used to it with a lot of trials in time

Binnur you talked about extra time in your post #8, there is no real formula to figure out the extra time needed. In Colin's post he stated that it was a 40 minute exposure, lets just say that the original time he worked out was 20 minutes, as the sun was going down he decided to add 1-stop more of time, well at 20 minutes 1 extra stop you make that 40 minutes now. Remember when making long exposures in the time frame of minutes, it can really be hard to over expose as to get just one extra stop you have to double the time.

Cheers: Allan

[John 2]

Binnur, only the first article covers the use of a GND filters. The table is for a straight forward 10x ND.

[John 2]

Binnur, a further thought. There are some Android apps that will do the calculation for you. No sure about Windows and I Phone though.

[Polar01]

Binnur: the 2nd link John sent is for 10 stops, the chart I e-mailed you will give you times for 10 stops and any other amount of stops. I did this as I use Lee GND filters (4"x6"), and I have the 2, 3, and 4 stops along with the ten stop, so I needed a chart that just gave more than the reading for 10 stops.

Cheers: Allan

[bnnrcn]

Thank you John. I noticed the second link later Also Allan e-mailed me another chart which contains other amounts of stops . So, I think there will be no problem with time calculations

Binnur, a further thought. There are some Android apps that will do the calculation for you. No sure about Windows and I Phone though.

[bnnrcn]

I tried the chart Allan, it is quite useful. Thanks again

Binnur: the 2nd link John sent is for 10 stops, the chart I e-mailed you will give you times for 10 stops and any other amount of stops. I did this as I use Lee GND filters (4"x6"), and I have the 2, 3, and 4 stops along with the ten stop, so I needed a chart that just gave more than the reading for 10 stops.

Cheers: Allan

[Polar01]

Binnur if you think it is useful and can figure out how to post it in the thread feel free to do so. I do not know to.

Cheers: Allan