Sigma 50mm f/1.4 Problems

[khendar]

I just got a hold of one of these lenses, after reading very favourable reviews and recommendations from some friends.

I've got it attached to my Nikon D40x but I'm having trouble getting good shots out of it. The focus seems to be slightly off a lot of the time, and most of my shots come out dark, grainy, and fuzzy. When using it in AF mode it seems to focus fine in the viewfinder but the shot comes out out of focus when I take it. Even in MF mode it doesn't seem to focus very well. The viewfinder and the final shot don't seem to have the same DOF so what I thought was in focus is often way out.

So far a lot of my test shots were taken in pretty low light in a restaurant and taken across a table so the subjects were a maximum of 2m away. I understand that shooting with the aperture wide open makes focussing difficult due to the extremely narrow DOF. I managed to improve things a little by putting it in full manual mode and tweaking the shutter and aperture but I'm still having difficulty getting decent shots. I got the lens partly for taking low light portraits at parties etc so its a bit disappointing that its so difficult getting it right.

Is using a fast 50mm in low light supposed to be this difficult ? Is this a learning curve thing ? Do I simply have to learn how to use the lens properly or is it possible that there is something wrong with my lens ? Am I expecting too much of the lens for it to be able to perform well in dim light ?

Cheers.

[ricktas]

Post some photos with EXIF embedded. It could be any number of reasons, and some samples could help us resolve it

[lay-z]

Here's some quick troubleshooting questions so that we have some more information to help you:

How are you achieving focus? Do you frame, focus lock then recompose?

Which focus mode are you using? AF-S, AF-A or AF-C?

How are you selecting your focus area? Single Point, dyanimic area or auto area?

Dark, Grainy and Fuzzy - What ISO are you shooting out? It sounds as though you are shooting in auto mode and the camera is selecting a high ISO.

What you see in the viewfinder and the DOF you produce in image are incomparable. I don't possess enough knowledge to explain why but I just know that's the case so I hope someone here can help explain it for you.

What shutter speeds are you shooting at in low light? Shooting at a low shutter speed will create blur if you don't have super steady hands and arms. As a general rule of thumb, your lowset shutter speed should be to that of your focal length. ie. 50mm = 1/50sec. However, because your D40x has a cropped sensor (which increases your view by 1.5x), the recommended shutter speed would be 1/80sec.

Getting to understand any new lens is a challenge and in due time, you will know how to use it to its potential. (To provide some insight, it took me about 6 months of constant use of my Sigma 30mm/1.4 before I could use it 'without thinking')

[Tannin]

Dark and grainy have nothing whatever to do with the lens. (Any lens.) These are exposure and noise management issues.

Fuzzy may or may not be a lens issue. The sensible thing to do is try it out under normal, familiar conditions - say daylight and f/5.6 and confirm that you are getting the expected results. Then extend the boundaries by (e.g,) opening up the aperture for narrower depth of field.

There are limits to what you can achieve indoors at night without flash. A fast lens can help, but careful attention to exposure, camera shake redction, white balance, and exact focus all are required things too. It's not easy! Remember that at f/1.4, your DOF is very thin.

Most likely, your new lens is fine and you just need to learn its limitations, and learn how to maximise your chances. Don't expect miracles - like everything that's worth doing, you are going to have to work at it.

[kiwi]

Test it in good light and in a stabilized (read tripod and still subject) and then report back

I often take crap photos under crap conditions but I don't blame my lens :-)

[khendar]

Yeah I'm fully prepared for the probability that its user error on my part. Perhaps I have unrealistic expectations as to how well the lens would do in low light situations. I haven't had a chance to test it in daylight/normal light yet but I'll give it a go this weekend and hopefully find out that the lens is fine. I'll post some examples of the issues I was having tonight when I get home.

[ving]

what kiwi said. take a shot in good light and see what happens. admittedly alot of people use lenses like this and expect to get great hand held shots in pitch black (have been there).

[ricktas]

Got any photos to show us yet?

[kiwi]

35 posts in 6 years.....you could be waiting for awhile :cool:

[khendar]

I realise my first mistake is the 1600 ISO setting, which would be responsible for the graininess. Believe it or not these are actually the better shots that I got. These have not yet been tweaked at all.


Click to embiggen.
http://timparkinson.net/images/tn_aber1.jpg (http://timparkinson.net/images/aber1.jpg)



F-Stop: F/1.4
Shutter Speed: 1/40s
Distance: 1.2m
Exposure Mode: Manual
ISO: 800

http://timparkinson.net/images/tn_aber2.jpg (http://timparkinson.net/images/aber2.jpg)

F-Stop: F/1.4
Shutter Speed: 1/40s
Distance: 1.5m
Exposure Mode: Manual
ISO: 800


http://timparkinson.net/images/tn_aber3.jpg (http://timparkinson.net/images/aber3.jpg)

Focussed on the eyes and the ear is in focus. I guess that's too be expected at 1.4 ? Otherwise not too bed.

F-Stop: F/1.4
Shutter Speed: 1/30s
Distance: 89cm
Exposure Mode: Aperture Priority
ISO: 1600


http://timparkinson.net/images/tn_aber4.jpg (http://timparkinson.net/images/aber4.jpg)

I'm guessing movement ? Slightly too long a shutter speed ?

F-Stop: F/1.8
Shutter Speed: 1/13s
Distance: 1.5m
Exposure Mode: Manual
ISO: 1600

http://timparkinson.net/images/tn_aber5.jpg (http://timparkinson.net/images/aber5.jpg)

Here I had focussed on the girl in the back in the viewfinder and the one in the front came out in focus.

F-Stop: F/2
Shutter Speed: 1/15s
Distance: 1.5m
Exposure Mode:Manual
ISO: 1600

[khendar]

Here's some quick troubleshooting questions so that we have some more information to help you:

How are you achieving focus? Do you frame, focus lock then recompose?

I try to do this.


Which focus mode are you using? AF-S, AF-A or AF-C?

AF-A - Haven't really figured out what these settings actually do yet :)


How are you selecting your focus area? Single Point, dyanimic area or auto area?

Dynamic Area - Again, haven't really played with these settings.


Dark, Grainy and Fuzzy - What ISO are you shooting out? It sounds as though you are shooting in auto mode and the camera is selecting a high ISO.

Seems that's definitely an issue. Most of the shots were at 1600 or 800


What you see in the viewfinder and the DOF you produce in image are incomparable. I don't possess enough knowledge to explain why but I just know that's the case so I hope someone here can help explain it for you.

So is that something that you just have to learn to compensate for ? Focus slightly in front of the subject and hope it comes out right ?


What shutter speeds are you shooting at in low light? Shooting at a low shutter speed will create blur if you don't have super steady hands and arms. As a general rule of thumb, your lowset shutter speed should be to that of your focal length. ie. 50mm = 1/50sec. However, because your D40x has a cropped sensor (which increases your view by 1.5x), the recommended shutter speed would be 1/80sec.

Also seems to be an issue. Shutter speeds were definitely below my focus length.

Cheers.

[Dylan & Marianne]

Just from a quick look at these ( I don't want to jump to too many assumptions) - but alot of the look to have motion blur either from not holding the camera still enough (with the 1/13 shot in particular) or from the shutter perhaps being not quick enough as you have pointed out. Also, in both the last image and the chap with the ear in focus, focus seems to be off centre - I'd check where your AF focal points were set to when taking these shots?

[lay-z]

I try to do this.



AF-A - Haven't really figured out what these settings actually do yet :)

In that case, it should be OK. However, to be on the safe side, try using AF-S when taking single shots.





Dynamic Area - Again, haven't really played with these settings.
This may be causing some problems here.
in #1, the person's left shoulder is in focus.
#3 has the collar in focus.
You state you are using dynamic area focus - this should allow you to select your focus point. When shooting portraits, select the focus point to the position of the eyes. (By doing so, you won't need to to compose, focus lock, recompose as mentioned above unless you are trying for more creative frames.



Seems that's definitely an issue. Most of the shots were at 1600 or 800
From experience with my D80, ISO 800 would be the absolute limit I'd ever push it to, and even then, I'd do EVERYTHING I possibly can before going that high.




So is that something that you just have to learn to compensate for ? Focus slightly in front of the subject and hope it comes out right ?
As mentioned before, i can't provide the right advice as I don't know how to explain it properly so I hope someone else can help you here. However as you gain more experience, you will notice different focal lengths will also affect your depth of field despite using the same aperture value.



Also seems to be an issue. Shutter speeds were definitely below my focus length.
It appears so. It appears you were shooting in a low light environment - did you consider using fill flash?

[arthurking83]

The images that are not sharp, are affected by camera shake, or subject movement.
All this leads to the inevitable conclusion that any problems are user based, and not gear based.
There is one image of a chap with a striped shirt, and while he is not sharp, there are parts of the shirt that are, so yet again we come back to the conclusion that operator error is the cause of any problems.

Also! Whilst it's handy that the lens can be opened up to a aperture value of f/1.4, doing so doesn't necessarily mean that you are going to get razor sharp detail quality. At it's widest aperture setting, it is an exceptional lens that produces it's best detail rendering, and the norm is for a slightly lower amount of contrast. This can be dealt with in PP with a good sharpening edit step, to produce a semi decent image.
I know for a fact that this lens works very well at up to f/1.8, and at f/2 and beyond, the performance level changes to excellent! :th3:

Sorry to say khendar but your technique needs a little bit of work..... and while you're at it, read up a little info on how each type of specific gear type works for a given set of variable conditions.

My favoured method of getting a 'usable shot' with this lens, in these types of conditions, is to use AF-C(continuous focus mode) and shoot a rapid set of images in succession.
Even at silly slow shutter speeds you can still get a half decent image of (slow) moving subjects in low light. It's about tracking the point of focus, as both of you move relative to each other, and making use that you have syncronised your movements. Tracking focus is easy, use AF-C mode! Syncing movements is harder, and it simply requires luck. This luck is easier to achieve when you use the fastest fps rate you can! :p

[farmer_rob]

You are asking a lot of the d40x autofocus - in my experience, the 3 focus points don't provide much flexibility. Also, I found that there was visible noise for anything over 400 ISO. (I had a d40x before my d7000.). Once you drop below f/2, focus is extremely hard to get right, and manual focus on the d40x is (in my experience) close to impossible - the viewfinder is too small and dark, with no real visual aids.

As suggested above, practice in decent light when it the shots aren't important, and you'll start to learn what works. (I thought the d40x was a good camera, and a f1.4 should enable you to get some great shots.)