Does a scratch on front element affect IQ?

SkipD wrote in post #2754692
There's a fair chance that the "scratch" is not, in fact, a scratch (meaning material has been either reshaped or removed from the lens) but instead material deposited on the lens. I have seen that numerous times, and after mentioning it to a couple of people on the forum here who were fretting about a scratch they were able to clean the "scratch" off their lens.

A very close examination of the lens in question, using a 10X magnifier, could reveal that the lens is quite a deal after all.

SkipD:

That's a very good point - two years ago while pusing my grand-daughter in a plastic swing, it bobbled and hit my coated plastic eyeglass lens. "Damn, I said, I have a scratch on the lens".

Several weeks later, after routine daily washing with soap and water and drying with a towel, I couldn't find the scratch. It had washed off. It wasn't a scratch, but a deposit of poly plastic from the swing.

Coatings on lenses (even plastic lenses) can be very tough. The OP could check this out.

On the other hand, I personally wouldn't bother - if it has been struck with something to make the "scratches" what other damage has occurred - like lens misalignment?

NWShooter wrote in post #2755601
The amount of time I've spent on it? What like 30 mins. total between calling Canon and typing a few messages here.

If 30 min. can educate me and ultimately save me $300-400 then, I think it's time well spent.

Thanks for the, um, input though

Chris

I see you've never traded the GBP/USD on Non Farm Payroll on the first Friday of the month. 1.29.29GMT to 1.30.29GMT; you can lose or save $3000-4000

I think, load of cobblers. love the expression.

all of the lens contributes to each point in the image. The crop sensor only sees the central points, but each of those recieves light from the whole lens.

while most of my gear still looks new it's only because I haven't had a chance to muck it up yet. I loved the fact that my 70-200 came looking a bit used, that way if i ever scratch it I won't care cause it's already scratched. What the point in owning stuff to just have it, use it til it falls apart!

So what is he asking $$$ for the lens? You said it was a 70-200... is it F2.8, F4? IS?

Not sure posting the pic would help you decide but I certinally don't see anything unethical about posting it. Plus a pic always spices up a story .

You might ask for some sample RAW shots sent to you. At least 4 total.

2 large Aperature - 1 @70mm and another @200mm
2 small Aperature - 1 @70mm and another @200mm

If the pics look good, just put a polarizing filter on and try to forget they're there.

I love the Service conversation BTW. They might have just answered the phone "Don't waste your breath telling me anything because I'm on Autopilot."

It's sad but sometimes I find it's better to just let the robots fill in their forms without offering further info.

illy wrote in post #2755750
I see you've never traded the GBP/USD on Non Farm Payroll on the first Friday of the month. 1.29.29GMT to 1.30.29GMT; you can lose or save $3000-4000

Illy,

that certainly sounds interesting.
However, looking at your gear list (no 1-series bodies, long L primes or fast zooms there), may I ask whether you managed to win or lose ?

If I consider the time I have spent here on the forum, I am going to be sick...

Best regards,
Andy

Purchased a beat up 300 f4 lens from a PJ with some minor scratches on the lens and some scratches on the body for $400. Have used that lens for 4 years, many pictures and have not noticed a single issue with it. Yes it looks ugly...who cares. Produces photos just as good as the brand new one on the shelf, but I saved $600 going this route. Now I don't worry too much if I damage the lens as I'll only be out $400. I'd say if you are getting a good price, go for it.

Some of this stuff makes me laugh seriously.. I have a canon 28-135mm in mint condition.. no scratches at all.. valued at around $500Cdn.. and I have a totally beat up Canon ef 70-200mm f/2.8 L lens.. it has loads of scratches in the front element.. too many to count.. well the scratches are actually just in the coating.. it also has a lot of internal dust... and the outside of the lens is beat up as well.. doesnt look pretty.. Well.. Lets just say that the beat up L lens still takes way better photos than a mint condition 28-135mm lens...And the scratches... I haven't actually seen a situation where they show up yet.. but they are just scratches in the coating. I am not sure about deep gouges, but scratches in the coating don't have enough detrimental effect in my L lens IQ to put it on par with my non L lens.

I'm using a scratched 24-105 on my 30D (bought it used at a great price & discount because of the scratch). Great pictures and I haven't had any problems with it at any aperture or in any situation I've shot. As long as it does its job, it will continue to stay on my camera.

Get sample shots as suggested above. If they turn out OK, then why worry? If the price is right and you can save some money, go for it.

It does not in any way affect the image quality.

Theoretically it does, but by about .00001 percent in sharpness and resolution.

I don't think you can really tell from what you are doing, ie the methodology of comparing two different lenses is flawed. The scratches will reduce contrast and introduce flare rather than show up in the image as a scratch.

You need to do comparative flare tests with the same lens before and after scratching or compare a good model of the lens with a scratched one. The test will need to be done in harsh backlighting possibly with a strong light source in the frame (unless the lens is completely stuffed).

A good test might be to take some wire wool to a filter and put it on the lens and do comparative with and without.

I do know from doing comparative flare tests a bit of dust or dried rain drops on an optical surface will add to flare so I am sure sufficient scratches will. But it would be difficult to attribute the reason for flare without a comparative test.

However, even quite heavy soiling and damage is unlikely to show in benign lighting.