Low light + 85mm 1.8 ---> 1/160 not enough?

Hi, I'm back from shooting a firework display. (not the fireworks but the people under!) I've put my t3i to manual, 1/160, f1.8, ISO 3600. Most pictures are correctly exposed or can be with a little push from Lightroom. However 75% of my pictures got some motion blur in it. I've selected 1/160 because I though it was roughly double of 85mm but now I am kicking myself because I am on a crop sensor and the 85mm is equivalent to a 136mm lens. I should have selected 1/320 or at least 1/250.

It was my first night shooting experience and I really had the time of my life trying to get my shots without anyone noticing me. It's more easy than I though. If you stay at the same place for a while, nobody notice you anymore.

Then, what do you think?? 85mm, f1.8, 1/320, ISO 3200 should do the trick?

Thanks

Edit: Now I read that the rule is to equal the mm... 1/50 for a 50mm lens. This is clearly not working for me for street photography as I tend to snap my shots quite fast.

You sure it's motion blur as opposed to focus/softness issues? Low light + shallow DoF could mean that you missed the intended focus point. Add to that some softness at 1.8 and high ISO noise.....

As said there could be 2 issues here. The camera shake rule won't apply for moving subjects, you'll more than likely need faster again.

You were on the right track previously when you mentioned that the crop factor needs to be applied. So a 50mm on a 1.6 crop would mean the rule of thumb would dictate 1/80 sec or less. Having said that much is up to the photographer. Some people are just not steady enough that the rule apples. Keep in mind that the rule is a throwback to the film days when there wasn't anything called crop factor.

I am assuming you have some fireworks tracks in the photos? If so examine them carefully. If you are holding the camera steady enough the tracks will form a nice smooth track. If you are not steady enough, you will see a jagged appearance to the tracks.

Crop factor doesn't directly impact handshake. The only relevant factor is pixel size. There's no difference in handshake tolerance between a 30D and a 5D II. Both require 25% faster speeds than film, which we might assume has 4000x2500 resolution in most cases. The 7D/60D/18MP et. al., with pixels 35% smaller on each axis than the other two digital bodies, will require shutter speeds another 35% faster.

On a modern cropped digital body or a full-frame sensor like the D800, I'd try for double the focal as a minimum.

I'll post some exemple:

Sharp enough for me:

Clearly I am not steady enough. But I have to admit that I tought I would be safe at 1/160 and didn't stop my breath or steady my arms against my chest or anything.

Problem is, I think if I push the shutter more, It will make the ISO noise stronger because of the darker, underexposed image. I was quite on the limit tonight.

How much gain in shutter speed f1.4 would make over f1.8?

There different f-stop scales but the most common is the full stop scale that runs from f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64. It goes higher but you aren't likely to find it on a lens.

To answer your question you need the 1/3 stop scale which runs from 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8... From 1.4 to 1.8 is two steps, thus 2/3 of a stop more. Holding f-stop the same, that's the equivalent of going from 1/160 sec to 1/100 sec.

A good guide to everything exposure related is at http://www.fredparker.​com/ultexp1.htm.

Ok thanks. 1.5x difference. Quite good.

Sad the Canon 50mm f1.4 is not as sharp wide open as the 85mm.

OP:
I don't see the example images.

KnightRT wrote in post #14905606
Crop factor doesn't directly impact handshake. The only relevant factor is pixel size. There's no difference in handshake tolerance between a 30D and a 5D II. Both require 25% faster speeds than film, which we might assume has 4000x2500 resolution in most cases. The 7D/60D/18MP et. al., with pixels 35% smaller on each axis than the other two digital bodies, will require shutter speeds another 35% faster.

What leads you to this peculiar conclusion?

The rule I was taught for hand held is you wanna try and get 3x the focal length. So if you're shooting an 85mm lens then you want a shutter speed of 1/255 so 1/250th or faster to prevent camera blur from hand shake. I personally do not have the most steady hands and so this holds true for me. This is not be the same for everyone as I know people who can hand hold a 500mm f/4 at 1/250th and get tack sharp images.

If shooting at such a low light is what you enjoy I would say you've maybe started to reach the limit of your body as your glass looks good. Perhaps upgrade a body that will allow you to push the ISO a bit more to get a faster shutter speed.

xarqi wrote in post #14906319
OP:
I don't see the example images.

OP didn't post .JPGs ... tried to display .PNGs

Ha yes, The hosting site kept them in PNG. I though it would be converted to jpeg. What browser are you using? It load ok on firefox but not on my Iphone.

(facepalm)
I've bought the T3i last month, and a 15-85mm few days ago! - Seriously, I enjoy shooting night time but I would rather get a 135mm f2L than a 5D markii.

Maybe next year!

For the handshake thing, one solution would be to use a 50mm lens and not the 85mm. That would make the 1/160 shutter speed ok. Also I just might try to jump to 1/320 and get away with it with the 85mm.

Should I dare bump the ISO to 6400?

I am slightly shocked. I've just tried the same settings with my 15-85mm lens. even at f5.6, 1/30, the 85mm end give me a lot more sharpness than the 85mm f1.8 at 1/160. The IS really make all the difference in the world.

However, yeah... no nice bokeh.

It also make me wonder about a lens like the 70-200mm f4 IS USM. It could actually be used in extreme low light at ISO 1600.
I was planning to get the 135L as my next lens. Now I am not so sure anymore.

John from PA wrote in post #14905763
There different f-stop scales but the most common is the full stop scale that runs from f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64. It goes higher but you aren't likely to find it on a lens.

To answer your question you need the 1/3 stop scale which runs from 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8... From 1.4 to 1.8 is two steps, thus 2/3 of a stop more. Holding f-stop the same, that's the equivalent of going from 1/160 sec to 1/100 sec.

A good guide to everything exposure related is at http://www.fredparker.​com/ultexp1.htm.

I think OP wanted to go from f1.8 to f1.4...Therefore the SS would go from 1/160 to 1/250.

Earwax69 wrote in post #14906567
Ha yes, The hosting site kept them in PNG. I though it would be converted to jpeg. What browser are you using? It load ok on firefox but not on my Iphone.

Firefox 3.6.28 on OS X 10.4.11.