Increasing DOF and sharpness in the Sigma 600mm reflex lens: I have this lens. I did a little experiment that improved the DOF and sharpness of the lens by reducing the f stop to f11...

Streets Loc: Euless, TX.

I have this lens. I did a little experiment that improved the DOF and sharpness of the lens by reducing the f stop to f11 from its intended f8. This was done by inserting a collapsible lens shade (made for a 62mm lens) that fit precisely into the standard lens shade (98.4mm I.D.) that came with the lens. Here are the test shots. You can immediately detect the DOF improvement and see the increased sharpness in the "made in Japan" area. The top photo was made without the inserted lens shade.

(Download)

Bill_de Loc: US

Have you applied for a patent yet? Good thinking and good results!

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chaman

You have just proved a well known fact. When a lens is stopped down (by whatever means) it shows increased sharpness. Of course now it needs even more light to get such an image. I dont know what your purpose with this is but if you are dreaming of making a reflex lens perform like a higher quality 600mm prime dont fool yourself.

Bill_de Loc: US

chaman wrote:

I dont know what your purpose with this is ...

Obviously he showed a relatively easy way to improve the results from the lens he has. I would have thought the pictures made it clear. I guess not to everybody.

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chaman

Bill_de wrote:

Obviously he showed a relatively easy way to improve the results from the lens he has. I would have thought the pictures made it clear. I guess not to everybody.

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Perhaps some simple minded individuals impress too easily....like you.

SnappyHappy Loc: Chapin, SC “The Capitol of Lake Murray”

I'm impressed too. Stopping down a FIXED aperture lens isn't as easy as turning a ring or dial.

MichaelH Loc: NorCal via Lansing, MI

chaman wrote:

You have just proved a well known fact. When a lens is stopped down (by whatever means) it shows increased sharpness. Of course now it needs even more light to get such an image. I dont know what your purpose with this is but if you are dreaming of making a reflex lens perform like a higher quality 600mm prime dont fool yourself.

It "shows increased sharpness" up to a point. Acceptable perceived depth of field (focus) does increase as the lens is stopped down but at some point sharpness decreases due to diffraction. I have tested some lenses that appeared to be as sharp at f/1.8 as at smaller apertures. But so far, none at f/22 that were as sharp as at f/11. I believe this is lens dependent and may not be the same for each lens even if it is the same model from the same manufacturer.

Streets Loc: Euless, TX.

chaman wrote:

Perhaps some simple minded individuals impress too easily....like you.

chaman, doing a bit of trolling? Sorry that this was not your thread? There must be a reason for your displeasure. I enjoy this sort of experimenting: It helped me put man on the moon when I worked for NASA.

MikeT9

Stopping down any lens will increase the depth of field, yes but not necessarily the image quality.

SteveR Loc: Michigan

Streets wrote:

I have this lens. I did a little experiment that ... (show quote)

How did inserting the 62mm lens shade contribute to allowing you to reducing the f stop? Was that the goal of using the smaller hood? Could the same result have been achieved by adjusting shutter speed or ISO?

Don't worry about Chaman....Mr. Negativity. The rest of us don't.

chaman

SteveR wrote:

How did inserting the 62mm lens shade contribute to allowing you to reducing the f stop? Was that the goal of using the smaller hood? Could the same result have been achieved by adjusting shutter speed or ISO?

Don't worry about Chaman....Mr. Negativity. The rest of us don't.

Like I said...simple minded impressed by simple, ALREADY KNOWN things. Lens may be sharper....IQ not.

Streets Loc: Euless, TX.

chaman wrote:

Like I said...simple minded impressed by simple, ALREADY KNOWN things. Lens may be sharper....IQ not.

Good God! Anyone ever tell you that silence is golden?

chaman

Streets wrote:

Good God! Anyone ever tell you that silence is golden?

A convenient saying for someone looking for positive reinforcement.....Anyone told you that posting in a public forum requires THICK skin? Did you believed that this experiment would automatically made people worship you or something? It was a waste of time, futile and I bet a lot think the same. I just decided to voice my opinion.

SteveR Loc: Michigan

chaman wrote:

A convenient saying for someone looking for positive reinforcement.....Anyone told you that posting in a public forum requires THICK skin? Did you believed that this experiment would automatically made people worship you or something? It was a waste of time, futile and I bet a lot think the same. I just decided to voice my opinion.

And we gave you a critique on what we think that opinion is worth!!

chaman

SteveR wrote:

And we gave you a critique on what we think that opinion is worth!!

And coming from a simple minded fool like you....you think I care? Invest you time trying to obtain a decent image worth looking.....my advice to you.