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Lets start by saying that i'm fairly new to photography and some of my questions might be to noob... [:)]
I'm looking to get a 50mm lens but i'm watching my spending (can't buy an L lens)...
Is there a significant difference between a 1.8 and 1.4 when we talk about DOF ?
Same question goes for speed , is there a significant difference when shooting in low light ?
Thanks !
f/1.8 is 2/3 of a stop slower than f/1.4. In terms of shutter speed that means 1/160th instead of 1/250th. f/1.8 is still VERY fast!
DoF: Assuming a subject distance of 10 feet the total DoF @ f/1.8 will be 0.81ft vs. 0.65ft @ f/1.4.
Check out Bryan's reviews of these two lenses. They are both great in their own right. Since you are new to photoprahy and the f/1.8 is SO cheap I'd consider buying that and finding its limitations before upgrading to the f/1.4. It's a fantastic lens and probably one of the best ways to spend $100 to improve both your understanding of and quality of your photopraphy.
Daniel will definitely answer this in a more detailed fashion, but here's my impression:
the difference between f/1.8 and f/1.4 is not HUGE, it's reasonable, though. Both give good DOF.
Now, comparing the 2 lenses:
the 50 1.8 doesn't have USM or an 8-blade aperture. Build quality is terrible. $90
the 50 1.4 has USM, and an 8-blade aperture. Build quality is reasonable. $300
The 1.4 @1.4 has the same sharpness of the 1.8 @1.8. and so forth. Point: with the 1.4 you can get sharp results at wider apertures (Daniel?)
my 2¢: get the 1.4
brendan
IMO, the biggest difference will be lens quality. I assume you're comparing the 50 1.4 to the "plastic fantastic" 50 1.8. The 1.4 is a better built, sharper lens.
Background blur quality is best seen in the three-way comparison, a little over halfway down this page
The actual depth of field is just a simple calculation. Look at your settings in a Depth of Field Calculator
Thanks guys... in terms of the built quality I know that the 1.4 is better, just like the 1.2 is even better. I was just wondering on the DOF more than anything, i want the blur effect on my portraits and didn't know if it was a significant difference between the 1.4 and 1.8...
I guess if the difference in Speed and DOF is not so big then it comes on to whether I want a better built with faster focusing or not ? because on the IQ side of it they are both good, right ?
BTW, i don't know if this will make a difference, but i have a 1.6 body
Quote:
Originally Posted by vitomalpi
Read the reviews. I want the blur effect too, but there's not a LOT of difference between f/1.4 and f/1.8. However, the f/1.8 lens isn't real sharp until f/2.8; the review says that the f/1.4 lens is sharp by f/2.0 and very sharp by f/2.8. Therefore, if you want sharpness, you can work one stop faster with the f/1.4 lens. That's a little more significant in my book.
Quote:
Originally Posted by vitomalpi
If blur is important to you, then you need the 50 1.4. The 1.8's 5-blade aperture will produce OOF pentagon highlights in blurred areas, the 1.4 will produce a nice, round blur effect.
There isa difference in speed and DOF between 1.4 and 1.8, it's not huge, though. The IQ of the 1.4 is superior. At comparable apertures the 1.4 dominates.
If you want the 1.8, remember that it's a great lens, but at the end of the day it's a $90 lens at it certainly feels like it.
brendan
Everyone else already answered your questions very well. The only thing that I would add is to encourage you to consider the Sigma 50mm f/1.4. It's another $150 or so, but almost everything about it is much better than the Canon 50mm f/1.4: contrast, resolution, bokeh, manual focus, etc. The only downside is that Sigma's QA is often not very good, and some buyers have gotten lenses that had to be returned. But then again, Canon's 50mm f/1.4 has poor build quality as well: one of (if not the most) highest repair rates of all Canon lenses. Whatever you end up with I'm sure you'll love it.