Filters are BAD! 120-300 2.8 sample photos

stylgeo

stylgeo

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I know that most of us have a UV or Skylight filter in front of most of our lenses just for protection. I know I do. The two lenses that I don't have a UV to protect the front element are my nifty 50 and the lensbaby. There are 2 reasons. First of all, when I had a cheap £5 UV on the nifty I noticed a great loss in IQ, so I took it off thinking that I should buy a better one. The second reason is why I never bothered buying any filters for these two lenses, and it's because they are so cheap that I didn't feel the pressure of doing it.

I've had my Sigma 120-300 f/2.8 for a year now and i've been more than happy with the results even wide open. What was bugging me was the loss of IQ when I used TCs on that lens. I ended up selling the 2X because it was just too bad and with the 1.4x I was always stopping it down to at least f/9 to get the results I was after. The interesting thing is that i was getting uniform results of bad IQ in all my photos. When shooting wide open at f/4 with the TC, from the middle of the frame and the right of it, the photos were really sharp, but in the left side of the frame it was just bad. I posted a thread here a while ago and you guys told me that it was probably due to misaligned elements in the lens and i needed to send it for repairs. i never found the time and opted to either use it without any TCs or just stopping down, which wasn't a problem during the summer since I was in Cyprus for 2 months and I was getting really fast shutterspeeds even at f/16. Coming back to the UK, I realised that I would really need to shoot wide open to get acceptable shutterspeeds. But it was really bugging me, so before deciding to send it to Sigma for repairs (I would have to pay for it since I bought it second hand and it's not under warranty anymore) i decided to give it a thorough test.

Looking to shoot something flat with lots of detail I ended up using the box of the ColourCatcher I'm using for my laundry :p. I had the camera on a sturdy tripod, connected via USB with my PC and controlling it remotely and using MLU with a remote shutter control. I went to great lengths to ensure that my plane of focus was parallel with my target and chose a single focusing point. I refocused for every shot and took several photos for every set-up and chose the best one for my comparisons.

The UV was the problem. And the funny thing is that it's not a cheap one.
It's a £100 Heliopan 105mm UV.

These are some 100% crops of my test. The centre focusing point was at the bottom right corner of the image with the hand and the number 1 on the top.

First some examples from a bit to the right of the centre point

f/4 with filter
3089787704_508c45c82e_o.jpg


f/4 without filter
3088951187_85881d040d_o.jpg


f/8 with filter
3089788038_98cbb1e430_o.jpg


f/8 without filter
3088951509_e0be762d2e_o.jpg


As you can see, there is little to no difference in these photos, except from the f/4 ones.
Now from the centre and a bit on the left of the same photos

f/4 with filter
3088951737_f61fd9132e_o.jpg


f/4 without filter
3089789040_20ce256d56_o.jpg


f/8 with filter
3089789302_8a138609ac_o.jpg


f/8 without filter
3089789666_883ea77ed3_o.jpg


As you can see, the problem I said before is evident in these photos. But what makes the filter affect the IQ in that way? Only on one side of the frame? What I know is that i wont be using it anymore that's for sure!
 
Did you know Sigma make a UV filter specifically for this lens, when I had the 120-300mm it was never off mine and I didn't have any problems with it
 
Although I'm happy with results from my 70-200 2.8 and 2x extender I'm going to have an experiment now...
 
wack61 said:
Did you know Sigma make a UV filter specifically for this lens, when I had the 120-300mm it was never off mine and I didn't have any problems with it
Click to expand...

...elaborate please...:shrug: is it just a Sigma 105mm UV or is it a particular filter?
 
It's the 105mm EX UV or the EX DG UV for the DG version.
 
Funnily enough it was this lens too that made me completely "anti-filter"

I was never happy with this lens until the very expensive Sigma 105mm filter came off.

I can also see differences with wide angle lenses for edge and corner accuity.
 
I never use a filter to protect my lenses, that is what insurance is for!

I know! Lets spend £100's or much much more on a specifically designed piece of photographic glass which has had engineers, expert designers and computers working out the best formula and requirements to engineer a finished lens. Then lets stick a cheapo piece of glass on the front.

Do you not think that if Canon, Nikon, Zeiss, Pentax etc thought that more glass was needed on the lens, they would have fitted it themselves?
 
EdBray said:
I never use a filter to protect my lenses, that is what insurance is for!

I know! Lets spend £100's or much much more on a specifically designed piece of photographic glass which has had engineers, expert designers and computers working out the best formula and requirements to engineer a finished lens. Then lets stick a cheapo piece of glass on the front.

Do you not think that if Canon, Nikon, Zeiss, Pentax etc thought that more glass was needed on the lens, they would have fitted it themselves?
Click to expand...

:agree::thankyou::plusone:
 
EdBray said:
I never use a filter to protect my lenses, that is what insurance is for!

I know! Lets spend £100's or much much more on a specifically designed piece of photographic glass which has had engineers, expert designers and computers working out the best formula and requirements to engineer a finished lens. Then lets stick a cheapo piece of glass on the front.

Do you not think that if Canon, Nikon, Zeiss, Pentax etc thought that more glass was needed on the lens, they would have fitted it themselves?
Click to expand...

Can agree there, but i was using the most expensive UV filter I could find, not a 'cheapo' one! I wouldn't want to scratch the front element but hey, I need to be more careful from now on! I'm getting rid of all my protective filters..

...goes to check the same thing with 10-20...
 
I did exactly the same thing with my 70-300, which I was thinking of selling... Glad I tested it because it's pin sharp without the filter.
Did the same test with the 18-200 and noticed no difference filter off or on, but I now shoot the 70-300 without a filter.
 
I used to use them but took them all off a few months ago. Not regretted it... yet!

I wonder if any of the lens manufacturers have ever considered designing in a user replaceable front element. :thinking:
 
Hood on and no filter here.

If it gets damaged then it will be a "oops I've dropped it down the stairs" insurance claim!
 
Well after seen those photos I'll be checking my 70-200 2.8 L tomorrow with and without the B&W filter.
 
Most of my lenses have filters on them and I am happy with the results.
 
The difference is quite obvious in these shots, but are these cropped right down? If so, how do they look un-cropped?
 
EdBray said:
I know! Lets spend £100's or much much more on a specifically designed piece of photographic glass which has had engineers, expert designers and computers working out the best formula and requirements to engineer a finished lens. Then lets stick a cheapo piece of glass on the front.
Click to expand...

Wholeheartedly agree!

I still keep my old filters on the lenses while in my camera bags but the minute I go to use them in anger?..........off they come.

I came to this conclusion after being really disappointed in my Canon 70-200mm f4. Took the carp filter off it and now I love it. It's actually exactly what I wanted and I use it a lot.
 
The Matt said:
The difference is quite obvious in these shots, but are these cropped right down? If so, how do they look un-cropped?
Click to expand...

Well yes they are 100% crops, but i don't understand what you mean when you say how they look uncropped. I will post an example of the full frame shot, but scaled down to a max of 800pixels for TP they all look the same.

The focusing point was at the bottom right corner of the little picture with the hand numbered 1.

3090419306_d9c95176df_o.jpg


I took 800x600 crops of every photo from the same spots, one spot from the middle and right and the other from the middle and left just to show the difference.
 
Apologies for the double post, the cat walked across the keyboard!
 
Back in the days of film, I always used either a skylight or UV filter. Now with digital and an L lens I just could not bring myself to put anything in front of the glass.

If I do something bad enough to damage the filter, there's a good chance it will damage the lens in any case.

The main reason for having so called protection filters was to negate colour cast which is now easy to do in post processing.
 
i will try some with and without filter when i next go out and see which o prefer. not had any issues with the UV Filter thats on mine however
 
whitey said:
i will try some with and without filter when i next go out and see which o prefer. not had any issues with the UV Filter thats on mine however
Click to expand...

Well, i never thought I had an issue with the filter until I started using TCs, that's when the problems started.

But I still can't understand how a filter could affect the lens in this particular way, ie having half of the photo soft and half sharp (ish). I did thorough tests without the filter and the lens seems not to suffer from any problems at all...

Wouldn't the filter affect the whole photo instead of the left half?
 
I was using filters, and I removed them as they affected the images. I still carry one around in my bag for occasions like when we went to Chessil beach and I used the filter to get covered in a salt water haze rather than the lens, but the conditions were so rough and grim anyway the loss in quality from the filter wasn't really an issue.
 
Flashman said:
I used to use them but took them all off a few months ago. Not regretted it... yet!

I wonder if any of the lens manufacturers have ever considered designing in a user replaceable front element. :thinking:
Click to expand...

I never use "protective" filters on my lenses either. The front element on the lens is the most important, it is this one that decides how much available light and its quality, actually get into the lens and onto the sensor. Lens manufacturers spend fortunes on developing lens coatings and most people just stick a cheap filter on the front. You may protect the expensive front element, but its expensive and at the front for a very good reason!

Allan
 
stylgeo said:
Well, i never thought I had an issue with the filter until I started using TCs, that's when the problems started.

But I still can't understand how a filter could affect the lens in this particular way, ie having half of the photo soft and half sharp (ish). I did thorough tests without the filter and the lens seems not to suffer from any problems at all...

Wouldn't the filter affect the whole photo instead of the left half?
Click to expand...

not to sure tbh. i would have said the whole photo though

i havent used mine with TC yet i dont think but will report back once i do
 
stylgeo said:
I know that most of us have a UV or Skylight filter in front of most of our lenses just for protection.
Click to expand...
Not me. I stopped a while ago when it was explained to me how little they protect the lens. You're better off with a lens hood to protect it.
 
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