Lens Woes!!! Canon Prime 50mm f 1.8

There's a few things to consider, but fundamentally, got some samples? It is easier to see than guess from a description.

Having said that, there are some things to consider as contributing factors.

If you're using the lens with the aperture set quite wide (f/1.8 or close to that) then the region in focus can be very thin. Of course this is the main reason for the lens to exist so you probably would be using it at least some of the time. It also depends on the subject distance too, but working fairly close, you could focus on the nose and the eyes will be out of focus for example. So focus accuracy is particularly important. When working at smaller apertures (like f/5.6 of kit lens) the area in focus is a lot bigger so will help mask any small errors. What do you want in focus? If there isn't enough, you will have to reduce the aperture size (increase f number).

AF might not be accurate enough, or possibly the lens and body are relatively out of alignment with each other and will always have an offset. The workaround there is manual focus in live view. I tend to use this on a tripod as even small movements can throw off the focus. Using a tripod also means you don't have to worry about motion blur with exposure time, so you can select a low ISO to keep noise low and improve visual quality.

 

I pretty much stopped using my kit lens when I got my 50mm/f1.8, and I get incredibly sharp photos with it. However:

- I almost always use a tripod.
- I almost never use autofocus.
- When using manual focus I use live view zoomed in 10x to focus my shot
- When using a tripod I use a 2-second auto-timer so my hands aren't on the camera when the shutter releases

That's how I took this photo.

This one I was hand-holding the camera and using auto focus, but it was pretty bright.

 

The minimum focal distance on that lens, auto focus or not, is 18 inches, so that's the nearest the subject can be for it to be able to focus at all. If you're getting closer than that, that could be your problem.

 

I usually use manual focus with my prime lens as I find the autofocus a bit lacking (and noisy!). To get sharp photos in low light, move up a stop or two from 1.8 (a lens is rarely at its sharpest on the widest aperture) and definitely use a tripod. I always use my camera on full manual and if I'm using a tripod I will set it to 100 ISO to get the least amount of grain possible, and then just play around with the shutter speed until the photos come out well exposed.

 

I honestly can't tell -- it'd be helpful if you could link to much larger versions of the images so I can figure out what's in focus and what's not. In the second image it looks like the fabric behind the doll may be in better focus than the doll but I can't really tell.

The other trick I forgot to mention is that I always focus on the eye nearest to me.

You might also want to try a smaller aperture -- something like 2.5 or 3 will still give you a pretty shallow depth of field, but it won't be as unforgiving as 1.8 as far as focus is concerned.

 

Also, what were your shutter speeds for these? In low indoor light, you might be having to leave the shutter open for an unfeasibly long time, which allows all sorts of random sensor activity to come into play. This can degrade the quality of the image. With low light it is often a matter of compromise between a fast ISO and a slow shutter speed, both of which carry their own problems. For informal, hand held photos (such as at meets) I go up to ISO 800 as I have shaky hands and can't take a decent photo at more than about 1/150. This tends to give the type of image degradation seen on yours. For shots where I have more time and my tripod, I go down to ISO 200, or 100 if I have lots of light and am feeling ambitious. BUT, I wouldn't go much above 1/50 to avoid that sort of graininess.

Personally, I never use live view to focus as, on my camera at least, it always looks blurry even if the final image is shapr enough. But manual focus without takes some patience and scrutiny, although it is definitely better than AF.

Could you do some experimenting with different ISOs and shutter speeds for the same lighting? That might help us see what's going on.

 

I think they look within expectations. They were both shot at f/1.8 which results in a very thin depth of field. The in focus region is very thin! Set a bit higher f number (try f/2.8, or even more) if you want more in focus, and it will also help increase sharpness for the parts already in focus. The 2nd photo is taken further away than the 1st, which increase the depth of field, so that would explain it looking sharper overall.

For reference, the exif reports both were taken at ISO800 at 1/80 and 1/50 respectively. Going down to ISO200 should be no problem. The further benefit down to ISO100 probably wont be noticeable. I wouldn't worry about long exposure noise until you're beyond 10 seconds. This assumes the tripod is stable enough not to introduce motion blur.

 

Popo, how did you get the exif info off these? I couldn't with Exif Reader. What are you using?

And, yes, ISO800 explains it. And, as has been said before, stretching your lens to f/1.8 wouldn't help. I'm not sure that the narrow depth of field on f/1.8 is explaining the lack of sharp focus anywhere though, Popo. And if you are still on 1/80 and 1/50 on those settings, I would suggest that your lights are not strong enough. Can you use brighter bulbs? or two lights?

 

To view the exif, I use Opanda IExif (+ optional FireFox plugin).

To soften light, you can try holding up white paper or fabric between the light and subject, but it will also "eat" a lot of the light too. If you're on a tripod, that wont be an issue as you can just expose longer to compensate.

 

When you're on full manual you should be able to change everything at will (that is, why it is called manual). You could try Apperture priority with exposure compensation if needed.

I second the "use a higher f-number". 1.8 is great if you absolutely need it, because you're handholding and just can't get enpugh light in. For dollyfotos I usually go to 2.8, that is still very shallow DOF, but it improves the sharpness of the lens immensely. a) it helps to eliminate the faults along the edges of a lens and b) it will help with focussing.

To little DOF is not good. At least the nearest eye should be almost if not completely in focus and if you are as close, as on the first picture, the DOF is hairthin.

 

The easy way would be to go into A mode, which lets you set the f number as desired, and set the shutter speed for you. You will probably also want to manually choose an ISO setting as otherwise on auto-ISO it'll probably go high. This assumes you're using a tripod.

 

Seconding Ookami and Popo, aperture priority is perhaps the most intuitive setting to use, with enough flexibility to do what you need to. It is not as flexible as Manual and you might find yourself needing to compensate up or down in certain situations (like a light doll on a dark background will need at least one stop down, to avoid the doll's skin being blown out), but perhaps that is for another day...

As for diffusing light, I would use something transluscent, rather than opaque fabric. That way you get to keep most of that precious light. There are lots of things you can use for that. I have a diffuser disc and some white brollies, neither of which were very expensive. I also use a transluscent white shower curtain. A plain, net curtain would also work well.

Do we get to see some of your experiments?

 

By George, she's done it! That is HEAPS better!

Personally, I prefer the diffused shots. They give more moulding to the face of the doll.

As for setting white balance with only two hands, I prop up a piece of white or grey card near the doll's face, using whatever Heath Robinson contraption I can set up, and then frame the shot to fill the viewfinder with the card and click away. Alternatively, I use my remote shutter release and hold the card in front of the doll, hoping I have filled the shot with the card. This is rather more hit-or-miss. Using auto WB is another option. It is far from perfect, but at least it would avoid the colour cast on these.

Bravo!

 

Wonderful, they look a lot sharper! I always adjust the white balance afterwards in Aperture, but I'm lazy.

 

Adjusting the WB in post is not a very good idea when you take your photos in jpg. Depending on the severity of the adjustment, the image quality will decrease imensely. In Raw-format, you will have to develop your picture afterwards anyways, so setting the whitebalance there is no problem. Raw is the unaltered information of the picture, jpg is already processed.

 

The remote cables are so cheap on eBay that there really is no excuse not to get one.

And will you start a new thread on moody lighting? I would like some more ideas on this as well.

 

LOL! The joys of experimentation!

You need to make sure that there is only one, focused light in the picture to get the low key, chiaroscuro effect, if that is what you are looking for (think David Bailey's portraits). Well, you might need some other lights to alleviate the gloom, but start with one, focused light (an anglepoise type thing, perhaps?) set at about 45 degrees to the nose of your subject and see how that goes.

Ah, have we already started the "moody lighting" convo? Perhaps I should sut up and wait for the new thread.

 

http://www.denofangels.com/forums/showthread.php?413676-Canon-Rebel-T1i-chat

This is also a bit of a tutorial, but MadamMauMau already said it