Hi everyone, I'm new to photography, so apologies if this is a very noob question. I have a Canon 1300d with two lenses - a Canon 70-300 IS USM and a Sigma 17-70mm f/2.8-4.0 HSM OC (the old one). I bought both lenses used while the camera was bought new and I've had it for years. I'm going on holiday tomorrow, and since I got both lenses recently, I thought I'd test them. I'm still learning, so I thought this would be a good opportunity to start teaching myself more about aperture, ISO, shutter speed etc. I played around with the 17-70 first. I have heard that aperture priority is useful for wildlife photography, I thought I'd try it out. At wide apertures, like f/3.5, the photos come out decently. Starting at about f/5.6, they start to become overexposed. I have tried various ISO settings, from auto, to 100, to 1600 (in the hopes that a lower ISO value would help). With the camera on aperture priority, I thought it would handle the shutter speed such that the image is properly exposed. I do check the exposure meter, and it looked like it was in the middle. I was using the viewfinder by the way. I tried the 70-300, and it was fine. I set the aperture to f/22, and the focal length to 70mm, and it produced normally exposed images. I zoomed the 17-70 to 70mm, set the aperture to f/22, and aperture priority produces overexposed garbage. I should mention that I can use exposure compensation to fix this for this lens. -2EV of exposure compensation produces a decently exposed image. I would like to know: 1. Is there any chance that the used lens is defective? Is this possible? 2. If the lens is not defective, what am I doing wrong? How would I get aperture priority to produce decent images without resorting to using exposure compensation? As I said, not necessary with the 70-300.
Okay I ran some tests on manual mode. I set the ISO to 100 and the aperture to f/13. Its a cloudy day here in England, but I left white balance on auto. Using manual mode, I pressed the shutter button halfway and watched the meter. When the bar was in the middle, I took a photo. This was at 1/6th of a second shutter speed, as recommended by the camera. Horribly overexposed. I raised the shutter speed to 1/13th of a second, which now showed as underexposed according to the metering. Shot came out better. Shot again at 1/50th of a second, camera says this is -2EV underexposed (if I read the meter correctly). Shot looks better, closer to life. Thoughts? Defective camera? Defective lens? I already know the photographer is defective! I can add photos if need be - just need to figure out how.
I’m not familiar with your camera but maybe it’s your metering mode. Are you using evaluative, partial, spot metering?
If one lens behave wells and the other does not is very likely that the lens with the problem is the issue, the camera should behave consistently. So 70mm at f22 should give the the same shutter and ISO combination. This can be observed if you look at the existence of light meters, ther read the light on an object and give you the shutter / aperture options as your film speed to expose correctly. Your camera may give a slightly different reading only because the meter is looking at the scene differently, it may be averaging a large chunk of the scene while the hand held meter is focused on a specific location in the frame. SO I would look at what the camera is trying to use for settings with both lenses at f22 like you were testing. You could also test the other end at 17mm and see how it performs, as well as try it wide open at f2.8 or 4 and maybe in the middle at f8 or 11. You may find it could get better or worse the more you stop down. If the camera is trying to use the same shutter and iso on both lenses at f22 then i bet the lens is not stopping all lthe way down and the aperture is getting stuck at maybe f11. This is my guess but more testing will tell, And if i'm right, may not have issues at the wider half of the apertures if the bladed are corroded or sticky and its simply not able to close all the way down. The lens could also be sending bad electrical signals to the camera as well but my bet is a mechanical failure. Try out some of the tests i mentioned but also pay attention to what ISO and Shutter speed are used when comparing both lenses at the same f stop. That will tell if the camera is trying to expose the same.
Thanks very much for your response johnsey. I contacted the seller and he suggested returning it for a full refund, which I did. I think something is faulty with the lens, but I don't know enough to know what or why. Had to send it today because I'm flying to South Africa tomorrow! That's what I wanted the other lens for. For the Kruger Park (our first destination), the 70-300mm is probably more useful. The 17-70 would have been useful for Cape Town and/or Franschoek - oh well. Smartphone will have to suffice.
Welcome to the Forum, Mr Blue, may I suggest you try Shutter Priority as wild life can move quite quickly. This is worth a try when you get back from your trip.
