Is my lens broken?

BunnyPics

BunnyPics

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Oksana
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Hello everyone

Can someone please shed some light onto my problem?

I have Nikon D5100 (I know, it's pretty basic...) and Sigma 18-250mm f/3.5-6.3 OS HSM Macro which I bought used from eBay. Since I've had it on, I noticed a huge reduction in sharpness of my photos. It's like there's always some micro-shake on all photos even when I hold my breath, shoot between heartbeats, and have OS on! Stupidly, I sold my kit lens now, so I borrowed a friend's camera with her kit lens to try and figure what's going on, whether it is my camera or my lens that is broken. She has similar (mine's D5100, her's D3200), and tested my camera with both lenses and hers with both lenses too.

I know my test is pretty rudimentary, but I think you can see the difference even in such a basic test. Both cameras were set on 1/500 shutter, max apperture the lens would allow, ISO 200, and focal length appx. 50mm. I am sure that the focus was definitely on the dot in the middle because on removal of the middle piece with the dot the cameras were hunting and not finding any focus points. Initially, I thought there was an autofocusing problem, but if you view these photos at 100% on Flickr, you will see that the sharpness is definitely sub-optimal in with Sigma lens on both cameras, and it's OK with Nikon lens on both cameras.

Is this Sigma lens broken? Thank you if you can help or advise.

My camera, Sigma lens

My camera, Nikon lens

Friend's camera, Sigma lens

Friend's camera, Nikon lens
 
You're right there is a noticeable difference. At first I thought the Sigma lens might be back or front focussing but to me it all looks pretty soft. You don't say which Nikon kit lens is being used but it definitely looks sharper on both cameras. Don't forget that the Sigma, with such a wide focal range, is quite a compromise......
 
I have never been a lover of these one size fits all lenses ,had one once sold it after a couple of weeks, I doubt it's broken it's just not a good one .when I was on Nikon I had a 55-300 v.r that's a super lens for the money
 
How sharp should each lens be?

A cheapish zoom, with a huge focal range, shot wide open, doesn't sound like a recipe for sharpness to me?

The trade off is you get to cover a huge focal range...
 
I have an 18-250mm zoom. I also have around ten other lenses. I got them because they're better in one respect or another than the 18-250mm. Roughly speaking, because it varies with focal length, it's pretty soft wide open, gets nearly as sharp as a good prime in the centre at around f8, and is nearly evenly sharp edge to edge at f11 although not as sharp in the centre as at f8. When I say as sharp as a good prime at f8, I mean when the prime is at f8. My primes are sharper at at wider apertures than f8, f8 already softening due to diffraction. I even have narrower range zooms that are sharper at f4 all through their range than this 18-250mm is at f8.

Yet that 18-250mm oom is still my most used lens, and has taken some of my best photographs. Nothing beats it for the speed with which I can grab an unexpected transient photo opportunity. It can have a good go at catching a bird in flight, a ship on the horizon, a sunset, or a bee in a flower. Sometimes I find such a good shot with it that I go back there with my best lens and a tripod to take the best I can. Often the difference is impossible to see on an A5 print, not easily noticed on an A4 print, and obvious on an A3 print at least to another photographer. Sometimes annoyingly I was so lucky with the light that first day with the 18-250mm that despite going back with my very best lens and a tripod at a number of carefully chosen times all I end up with are sharper but obviously inferior shots.

Don't let perfectionism strangle your photography. All lenses are imperfect trade offs between different incompatible features. Get to know their limitations, how to get the best from each. Sharpness is often over-rated simply because it's easily tested.
 
Yeah, looks to be about what I'd expect from a cheap superzoom but Chris speaks sense, it is all one big compromise and you need to decide what yours are.
 
Broken, no.

Not as sharp as your kit lens, absolutely. The kit lens is quite good for the money and has a much smaller zoom range. They are usually quite sharp as a short zoom range means fewer optical compromises.Sigma superzoom, shot wide open, I'm afraid the quality is not going to be close.

I would attempt to source a new kit lens, pick up something in the 55-200mm range as a second lens, and move that sigma on. Unless of course you can take a dip in quality as a compromise for the convenience of a bigger zoom. Of course if you will only ever put one lens on your DSLR, it negates a lot of the benefits of having it over, say, a bridge camera.
 
Dirty maybe

I agree with the others that the Sigma lens won't be as sharp as the Nikon kit lens especially with the aperture fully. I have seen a similar effect on a canon zoom lens that had mould growth on an internal lens element. As the lens is an eBay purchase I would check that it is clean and bright internally. With the aperture fully open shine a bright light (a little led light works fine) from the rear and look into the lens from the top from varying angles. You can compare what you see with your friends lens, ignore the odd spec of dust but if you see a white fluffy cast or haze and this wasn't expressly stated in the listing then alert the seller and return the lens as not as described.
 
Since you are photographing captive pet rabbits perhaps you would be better off with a 50mm or somewhat longer prime lens. I can't see why you would need the nearly 400mm equivalent of your zoom lens.
 
Nawty said:
Yeah, looks to be about what I'd expect from a cheap superzoom but Chris speaks sense, it is all one big compromise and you need to decide what yours are.
Click to expand...
^ that

Cheap/budget "do it all" lenses inevitably have compromises, and this type of lens will never give the best results and will be worst in anything other than perfect light.
 
TheDrift- said:
How sharp should each lens be?

A cheapish zoom, with a huge focal range, shot wide open, doesn't sound like a recipe for sharpness to me?

The trade off is you get to cover a huge focal range...
Click to expand...

I'm such a muppet. I never thought to close it down a little. I just did some very rough tests and yes, when I close it to 9 or so, it is a lot sharper.
 
chris malcolm said:
I have an 18-250mm zoom. I also have around ten other lenses. I got them because they're better in one respect or another than the 18-250mm. Roughly speaking, because it varies with focal length, it's pretty soft wide open, gets nearly as sharp as a good prime in the centre at around f8, and is nearly evenly sharp edge to edge at f11 although not as sharp in the centre as at f8. When I say as sharp as a good prime at f8, I mean when the prime is at f8. My primes are sharper at at wider apertures than f8, f8 already softening due to diffraction. I even have narrower range zooms that are sharper at f4 all through their range than this 18-250mm is at f8.

Yet that 18-250mm oom is still my most used lens, and has taken some of my best photographs. Nothing beats it for the speed with which I can grab an unexpected transient photo opportunity. It can have a good go at catching a bird in flight, a ship on the horizon, a sunset, or a bee in a flower. Sometimes I find such a good shot with it that I go back there with my best lens and a tripod to take the best I can. Often the difference is impossible to see on an A5 print, not easily noticed on an A4 print, and obvious on an A3 print at least to another photographer. Sometimes annoyingly I was so lucky with the light that first day with the 18-250mm that despite going back with my very best lens and a tripod at a number of carefully chosen times all I end up with are sharper but obviously inferior shots.

Don't let perfectionism strangle your photography. All lenses are imperfect trade offs between different incompatible features. Get to know their limitations, how to get the best from each. Sharpness is often over-rated simply because it's easily tested.
Click to expand...

Thank you so much for your response and for such a detailed write-up. I completely agree with you re. perfectionism and really everything you say.

I actually really enjoy the convenience of a zoom lens and I just realised THE OBVIOUS after reading some posts here--that I had my aperture wide open on it! I'm such a noob. So yes, of course, it was not as sharp as it could be. It's a good lens and I guess would be particularly good for travelling. Too soft for me though because I shoot animals and I want their hairs SHARP. Also that long 250mm is not useful for me - my photos are 50-80mm (75-120mm equivalent focal length). So I think I am paying the price in sharpness for the focal length I won't use. I will consider getting a Nikon 18-70mm instead. Quite fast for a budget zoom lens and should be a bit sharper at open apertures.
 
sphexx said:
Since you are photographing captive pet rabbits perhaps you would be better off with a 50mm or somewhat longer prime lens. I can't see why you would need the nearly 400mm equivalent of your zoom lens.
Click to expand...

I completely agree now. Nikon 50mm f1.8D is the one I'll be looking to get. It looks like I'll have to learn to zoom with my legs if I want sharp hairs.
 
Ripcurler said:
Dirty maybe

I agree with the others that the Sigma lens won't be as sharp as the Nikon kit lens especially with the aperture fully. I have seen a similar effect on a canon zoom lens that had mould growth on an internal lens element. As the lens is an eBay purchase I would check that it is clean and bright internally. With the aperture fully open shine a bright light (a little led light works fine) from the rear and look into the lens from the top from varying angles. You can compare what you see with your friends lens, ignore the odd spec of dust but if you see a white fluffy cast or haze and this wasn't expressly stated in the listing then alert the seller and return the lens as not as described.
Click to expand...

It looks very clean, it came in as new condition. Thanks for the great tip though, I will know how to check them for mould now :-)
I closed the aperture a bit and the sharpness did improve, but still not what I look for. I did get money for it back from PayPal and they told me to keep the lens too! But I feel bad about that now because I don't think there is actually anything wrong with the lens :-/ I kicked up such a fuss, they just wanted me to shut up, I guess.
 
Hi Oksana, I have changed my view on lenses and shooting recently, having changed camera systems and therefore had to invest in a couple of new lenses. I used to have a walkabout 17-50 on my crop body which was definitely my go-to lens. I found the ability to zoom and capture what was in front of me (except for telephoto lengths) ideal. As with most zooms, there were some compromises in terms of quality etc., but that flexibility was "essential" as far as I saw it.

The last couple of weeks have been different with my new camera. I'm almost exclusively walking around with an 85mm prime attached, even though I have a 24-70 zoom which is not far off the equivalent focal range of my last combination (this one is full frame). Instead of shooting what's in front of me, I'm actively looking for opportunities that will fit into that frame - and moving myself around to accommodate it.

The reason for saying all that is whilst a zoom lens is great for being flexible and your long zoom is a real jack-of-all-trades, that makes it perversely limiting. You've identified the quality/sharpness issue which will probably limit your use of it wide open (and its wide open is nothing like a fast prime). It is also more likely to make you static when composing, which is probably more severely limiting than any features of a lens itself.

Rather than change your zoom for a different/better zoom, I'd be tempted to try a prime lens if you don't already have one. If you use Lightroom you should be able to look at your photos as an entire collection and see what focal lengths you've been shooting at most frequently. You could get a prime that corresponds closest to that.

I'll be honest and say this is something that's worked for me and it might well not work for you. But it is a very cost effective way of complementing your existing lens with something that will be super-sharp, very fast, cheap, light and force you into composing your shots differently. For me that was great, but as always YMMV!
 
Agree with previous comments about so called super zooms etc ...
BunnyPics said:
I completely agree now. Nikon 50mm f1.8D is the one I'll be looking to get. It looks like I'll have to learn to zoom with my legs if I want sharp hairs.
Click to expand...
This lens will not auto focus on your D5100, if you need or want auto focus get the 50mm f1.8g in it's place, it is a better lens all round and the difference in cost is small.
 
PaulButler said:
Agree with previous comments about so called super zooms etc ...

This lens will not auto focus on your D5100, if you need or want auto focus get the 50mm f1.8g in it's place, it is a better lens all round and the difference in cost is small.
Click to expand...

I'm getting D300s. It will autofocus then :-)
 
What ever anyone does, do not do this test with the Nikon 58mm 1.4...... You might cry.
 
One thing that takes away sharpness when photographing animals is their movement, even when sitting and chewing they are still moving. By keeping the shutter speed up you freeze their movement. Looking through your Flickr there are a few images where you were below 1/100sec even as low as 1/25sec, these would allow time for the animals movement to cause slight motion blur and loss of sharpness. Keeping about 1/250sec may help increase sharpness.

A month ago whilst out photographing Red Squirrels I found afterwards images below 1/800sec were not as sharp as those above 1/800, it wasn't a camera/lens movement issue as I was above the 1/200 threshold for the 1/focal length hand holding rule, it was simply their movement at shutter speeds of 1/250 to 1/500 caused motion blur that reduced sharpness.

Lenses can cause loss of sharpness when used wide open, generally it depends on the lens used like has been said above.
 
rob-nikon said:
One thing that takes away sharpness when photographing animals is their movement, even when sitting and chewing they are still moving. By keeping the shutter speed up you freeze their movement. Looking through your Flickr there are a few images where you were below 1/100sec even as low as 1/25sec, these would allow time for the animals movement to cause slight motion blur and loss of sharpness. Keeping about 1/250sec may help increase sharpness.

A month ago whilst out photographing Red Squirrels I found afterwards images below 1/800sec were not as sharp as those above 1/800, it wasn't a camera/lens movement issue as I was above the 1/200 threshold for the 1/focal length hand holding rule, it was simply their movement at shutter speeds of 1/250 to 1/500 caused motion blur that reduced sharpness.

Lenses can cause loss of sharpness when used wide open, generally it depends on the lens used like has been said above.
Click to expand...

The photos above were taken on a tripod with a remote shutter release. With my animals, I do need to have quick shutter, yes. Captive rabbits are not squirrels, but still 1/200 or shorter is required. That's my main reason for upgrading the camera now to D300s - D5100 will not sync with flash above 1/200. And because I photograph indoors, I want a flash. I also want a shutter shorter than 1/200. It drove me crazy for months why I couldn't set a shorter shutter with a flash on. Now, I know!
 
BunnyPics said:
The photos above were taken on a tripod with a remote shutter release. With my animals, I do need to have quick shutter, yes. Captive rabbits are not squirrels, but still 1/200 or shorter is required. That's my main reason for upgrading the camera now to D300s - D5100 will not sync with flash above 1/200. And because I photograph indoors, I want a flash. I also want a shutter shorter than 1/200. It drove me crazy for months why I couldn't set a shorter shutter with a flash on. Now, I know!
Click to expand...

If you're using flash then the subject will be frozen irrespective of your shutter speed (assuming the flash is acting as a key light rather than a low level of fill). The flash duration is far, far quicker than the shutter speeds (unless your camera goes to 1/8000) so that's not really a relevant factor.

If you're shooting without flash then you'll need to up your ISO, widen your aperture and get that shutter speed faster. If you're using flash then it's a different technique - use your shutter speed to balance the ambient (slower shutter = lighter background, faster shutter = darker background)
 
BunnyPics said:
I just found these photos I took with that Sigma. I don't want to get rid of it now!!! It's definitely sharp and there's nothing wrong with it.
https://www.talkphotography.co.uk/threads/smudges-last-day.622408/
Click to expand...
I have this lens also and like yourself know there are compromises given the vast difference in focal length.

I recently considered getting rid of it as the first 50mm of the range is covered by my Sigma 17-50, but for the price I paid for it I think I'll just keep it tbh. For one, it's a good walkabout lens when I want the option for a bit more length, and secondly it gives me the ability to focus far closer than any of my other lenses without having a dedicated Macro lens.

I may find that I'll want something sharper long term to compliment my 17-50 (perhaps a 55-300 or similar), but for now I'll just stick with what I have :)
 
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