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CANON EF200L PRIME LENS

ollypenrice

By ollypenrice
in Member Equipment Reviews

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Wobbly Bob

Wobbly Bob

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Almost from my very first SLR camera (50 odd years aga) a filter of some sort, usually a UV was screwed in front of the lens and so when I recieved the EF200L, a UV filter was purchased and screwed on the lens. Took a picture of the moon a couple of weeks back and noticed a huge flair on the image, then took 10 x 2min subs of M42 all out of focus (yes focussing IS critical on this lens) anyway I noticed that the stars displayed an odd barrel shape and on magnification showed angled lines on each star. Well did some tests with the filter on and off which clearly showed the filter was the culprit. My question to you DSLR imagers is, do you fit a filter to protect the expensive glass on your lens ?.

On reflection, we dont fit filter's on the front of a refractor, so :)

Bob

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Photosbykev

Photosbykev

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People tend to think a UV filter will protect the front lens element if they drop it and it is almost an automatic reaction to fit a filter. Even the expensive multi-coated UV filters can degrade image quality especially if there are strong highlights in the view.

Personally I prefer to use a good lens hood and use filters only to balance foreground/sky exposures, maybe a polariser for controlling reflections or ND filters to give more control over the exposure. The only exception to that is when I'm shooting on a beach when I do use a UV filter purely to keep the salt and sand off the glass. When I've finished with them they go back in the case.

Why spend a lot of money on high quality glassware and then throw a filter on it which isn't doing anything to improve the image? Spend the money on a good lens hood.

For astrophotography you would be hard pushed to find a UV filter big enough for even a budget scope

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brianb

brianb

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did some tests with the filter on and off which clearly showed the filter was the culprit.

What brand filter?

They tend to be not quite optically perfect but you shouldn't have issues with a 200mm lens unless you bought a cheapie ... in which case it might be awful ...

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brianb

brianb

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It was a Jessops filter

Yup, that explains all ... an expensive cheapie ... the only filters that are worth buying are genuine Hoya or B+W, a decent "protector" filter for a lens with a 62mm filter thread will set you back something of the order of £42.90.

Very worthwhile if you often shoot in dusty or wet conditions (to save having to clean the front element of the lens so often - these are usually made of very soft glass so scratch more easily than filters, which can of course be replaced). No help for astronomy.

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ollypenrice

ollypenrice

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I will use a dewheater when necessary and keep the lens inside when not needed but I don't want extraneous glass in the optical path, for sure.

This is such an exciting addition to our setups, though. I am seriously thinking about buying two lenses to make a parallel OSC/Narrowband Two Shooter because good widefield images are less common than good telescopic ones and the connections between deep sky objects are fascinating....

Olly

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ashworthacca

ashworthacca

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Billy got bored...

Not with the thread but with the weather....

Canon%2070-200%20f4L%20Bahtinov%20Mask.jpg

Billy...

That's not to scale is it? Can you post one up at the size it needs to be cut?

I contacted Keith at Morris Engraving and he says that assuming I need it to be 80mm (the dia of my lens hood) the slots would only be 0.7mm wide. He couldn't do that with his laser, especially out of 3mm thick acrylic.

Any ideas?

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ollypenrice

ollypenrice

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Thanks guys, it looks like I'll stick to using Liveview (and fingers crossed) only for now.

Regards

You'll struggle. It is beyond belief, the sensitivity to focus. The smallest movements I can make are too coarse so I just go back and forth till I get a low FWHM. But surely there will be some FWHM software out there to use with your DSLR? I don't know my way around the DSLR scene at all, I'm afraid. I seem to have heard of DSLR Focus and FocusMax...

Olly

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ashworthacca

ashworthacca

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You'll struggle. It is beyond belief, the sensitivity to focus. The smallest movements I can make are too coarse so I just go back and forth till I get a low FWHM. But surely there will be some FWHM software out there to use with your DSLR? I don't know my way around the DSLR scene at all, I'm afraid. I seem to have heard of DSLR Focus and FocusMax...

Olly

Hi Olly, yes there is...I use APT but I was hoping to do away with having to connect to my laptop whilst using my Astrotrac. If I can I have a pretty good and very portable widefield setup.

It's looking clear tonight so I may get my first run out with the 70-200 so I'll see how it goes.

Thanks Olly.

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davew

davew

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If you want quick, simple and cheap try the Y mask. You've nothing to loose.

It consists of a bit of plastic from a food container lid. Angles as per the Bahtinov. It can even be made " In the field " with a pair of scissors if you forget your very expensive one.

Mine is the super deluxe version with cast off matches to attach to the dew shield. Note the hyper deluxe in the back ground.

Dave.

The mask result is from a 105mm camera lens

post-13139-133877528938_thumb.jpg

post-13139-133877528951_thumb.jpg

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Infinity

Infinity

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I only picked my astrotrac last weekend, so haven't had the opportunity to try it yet.

On the filter front i recently got a 77mm Hoya one, pretty pricey at around £70, but probably a good investment, My camera and 24-105L recently took a tumble (in a padded case) the front corner of the lens took the force of the impact. The filter saved the lens from damage, but the filter did crack. Probably saved an expensive repair.

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davew

davew

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Hi Martin,

I made the arms 4mm wide. It seems to work on every thing from a 50mm camera lens to a 630mm refactor. However, you will need to zoom in quite a bit when used with a small lens just to see the cross. I suppose the same thing would happen with a Bahtinov mask.

Thin arms do make the Y mask fragile so use a good piece of plastic not paper. I've used mine for around a year I think.

Experiment with the width.

Dave.

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Psychobilly

Psychobilly

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I have just won myself a copy of APT at 'the other place' so I look forward to having a play. Although I don't have a modded DSLR I think it is maybe time that I should. Big chip, 200L lens... Hmmmmm...

Olly

Go on .. you know you want to.... very handy for coloured starfilelds with your Registar expertise....

And you'll have remote manual or autofocus :(

Billy...

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Photosbykev

Photosbykev

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I have just won myself a copy of APT at 'the other place' so I look forward to having a play. Although I don't have a modded DSLR I think it is maybe time that I should. Big chip, 200L lens... Hmmmmm...

Olly

prime lens and 35mm sensors were made for each other :(
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