lens question

[eric's reef]

i have the rebel xt with a sigma 18-125 lens. I took a trip to the tampa aquarium and ended up with quite subpar pictures. most of the indoor pictures came out quite dark when shooting on the auto mode. i know the 18-125 lens is a little slow but i'm not sure what to change on the camera despite reading the book. i will be heading to macna and want to know what other lens would be a good choice to get or camera setting to use?
i was thinking on getting a 50mm prime lens but again i'm not sure it's the lens fault for the crappy pics. the camera takes good pics of the tank though, i will try to post some examples when i get home. thanks for your time eric

 

[Blazer88]

The Sigma 18-125mm gets ok reviews from www.fredmiranda.com, it defentially doesn't seem like Sigma's sharpest or fastest lens. I would say shooting in the Auto mode doesn't help at all as well. Since the lens is rather on the slow side, I would shoot in aperture priority and use a wide aperture to get a faster shutter speed, hopefully eliminating some blur. I have Canon's 50mm f/1.8 and it's a great lens to have, very fast, sharp, and cheap. The large aperture of the 50mm works great for low-light situations. Are you shooting in RAW or just jpeg? Post up some samples so we can see what you ended up with.

 

[eric's reef]

so far i was only shooting in jpeg, but plan on changing to shoot both jpeg and raw. when i get home later this evening i will post some pics. thanks eric

 

[astrogazer]

I'm a Nikon guy not a Cannon guru, but you may wish to check your exposure metering mode, I tend to like a 'spot' metering type of mode, and I can use the "spot" to 'meter' my exposure either towards the highlights or towards the shadows depending on the image and the subject matter, this just gives 'me' more control at the time of exposure. If you're metering more of the overall scene the majority of the time you'll get what you're looking at, however there are times...

 

[eric's reef]

well lets see if this works

 

[eric's reef]

how do i make these bigger?

and this one of my mom and dad, i tried to use a tripod and i think it is still not quite right

 

[Blazer88]

It seems that flickr.com is re-sizing the pictures for you. I'll PM you my e-mail address to see if you can e-mail me a few of the full-sized jpegs straight from the camera.

 

[reefrunner69]

Whether it's the lens or not, you should get the 50mm f/1.8 it's a great lens and cheap.

What ISO were you shooting at?

there are three parts to your exposure.
1) Shutterspeed
2 Aperture
3) ISO

All of these are the exact same exposure.

ISO 100
1/100th
f/8

ISO 200
1/200th
f/8

ISO 200
1/100th
f/11

ISO 400
1/400th
f/8

ISO 400
1/100th
f/16

As you can see they all work together. That's not to say you can always get that particular exposure, but you can see as you change one factor in the exposure you have to change one or both of the others.

 

[BlueCorn]

<a href=showthread.php?s=&postid=8010463#post8010463 target=_blank>Originally posted</a> by reefrunner69
All of these are the exact same exposure.

ISO 100
1/100th
f/8

ISO 200
1/200th
f/8

ISO 200
1/100th
f/11

ISO 400
1/400th
f/8

ISO 400
1/100th

But not the same picture.

I agree that the 50 1.8 is a nice addition and you'll get a lot of use from it. As noted, in low light ISO is your friend. While you don't want to be shooting at 1600 all the time, it can be very helpful in low light situations.

 

[eric's reef]

so what would be a good lens to take to macna? whats a better general purpose lens thats not at an "L" series price? eric

 

[reefrunner69]

I imagine that's why I used the term exposure

Depending on the lens used distance to subject etc...all those other things that go into DOF, the only real difference in the picture will be noise levels and possibly some additional DOF when stopping down to f/11 and f/16. The exposure will be the same.

 

[eric's reef]

lets see if this is any bigger.

 

[eric's reef]

wow to big, sorry eric

 

[eric's reef]

lets see how big this is.

 

[eric's reef]

here is the information on the photo
http://flickr.com/photo_exif.gne?id=224208365

 

[Blazer88]

What editing software are you using to to resize the pictures? For some reason it is stripping the exif data from them (which I need). Can you e-mail me one that is straight from the camera and not posted from flickr.com?

 

[eric's reef]

blazer check out this link for the exif for the last picture.
http://flickr.com/photo_exif.gne?id=224208365

 

[eric's reef]

but i will email you pics tonight. thanks again for your time. eric

 

[BlueCorn]

I can see that you used a flash on that shot so this is slightly moot....

One rule of thumb is to keep the shutter speed above the focal length of the lens for a sharp image. i.e. on a 50mm lens, 1/50th is the slowest you should attempt without a tripod or flash.

 

[Blazer88]

I saw the EXIF data from flickr. I have a program that does some cool corrections based on the camera/lens/focal length used to take the picture but the exif data has to be on the jpeg itself. But if you e-mail me a few that should work out just fine.