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07-03-2011, 03:51 PM   #1
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strange lens test results?

So I'm stuck home alone without the car (the family is at a church assembly out of town all day). Its a rare instance where the kids are not home for a long time and I can pull all the camera gear out without fear of destruction.
So I decided to print a lens resolution chart, take pictures and see how some lenses compared. I know its not perfectly controlled or scientific and printed charts have limitations, but its just to see how lenses compare out of curiosity. 4 primes and 3 wide zooms that cross the 50mm mark all score the exact same. To the naked eye, the chart has distinct lines up to 3 levels past where the camera scored (maybe further, to small to tell with the naked eye), so I assume its not the chart? All I can guess is that all these lenses have better resolution capabilities than my old lowly ist-ds and the camera is the limitation?

Something else weird. All are old MF film lenses except the ist-ds kit lens. I would have assumed that they would all have a different field of view due to crop factor than the kit lens, but the kit lens set at 50mm, had the same field of view as all the rest at 50mm? Did they provide a full frame kit lens with that camera or am I misunderstanding how cop factor works? Is it that any lens, new or old will have the same field of view with my camera, but my lenses will have a different field of view on a full frame camera? I guess that makes more sense but I had always thought that an old film lens would have a different field of view on my camera than a newer lens designed for the smaller sensor would?

Im not sure that it matters, but the shots were taken outdoors on the porch for brighter light (sun behind the house so no glare problems etc). The chart was taped up to a large square pillar that supports the upper level of the house above the porch and a tripod was used. All lenses were 50mm Or set to 50mm.

If it matters, lenses are
sears 50mm 1.7
chinon 50mm 1.9
ricoh 50mm 2.0
olympus f.zuiko 50mm 1.8 (modified pk mount)
vivitar 35-70 2.8-3.8 push pull
ist-ds kit lens
quantaray 35-70 3.5-4.5

07-03-2011, 04:06 PM   #2
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You are indeed probably camera limited. Perhaps also ability-to-manual-focus-accurately limited.

As for crop factor, you might want to start doing some googling to clear up your misconceptions. But the short answer is, crop factors don't apply when comparing different lenses on one camera. They apply when comparing the same lens on different cameras.
07-03-2011, 04:29 PM   #3
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I was worried that my ability to manual focus might cause problems as I am new to manual focus lenses. My camera is set to detect and indicate when the lens is focused. Basically I used 3 factors. I swung the focus back and forth to find where the field of focus was. Basically it had to seem to be in the middle of where it went in and out of focus on each side, needed to look in focus to me, and had to trigger the cameras in focus indicator light and the light had to stay on. I also took a few good shots with each lens. There were a few shots that seemed like they had suffered a little from focus but not enough to significantly alter the results. Its about the best method I could come up with.

As far as crop factor, now it makes sense and I understand it(it didn't fully make sense before, probably because I was wrong about how it worked).


QuoteOriginally posted by Marc Sabatella Quote
You are indeed probably camera limited. Perhaps also ability-to-manual-focus-accurately limited.

As for crop factor, you might want to start doing some googling to clear up your misconceptions. But the short answer is, crop factors don't apply when comparing different lenses on one camera. They apply when comparing the same lens on different cameras.
07-03-2011, 09:30 PM   #4
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Forget the word crop factor. Used on the same format, 50mm lens is as much 50mm as any other 50mm regrdless what age and format it was made for. The FOV will be the same whether you use DA set at 50mm, FA50mm, K50 or some 645 50mm....

07-03-2011, 09:42 PM   #5
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Try to focus by using Live-View mode with a tripod.
07-03-2011, 10:22 PM   #6
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Live View is not a *ist DS feature.

If your test chart was right in the center of the frame, you might have just shown that a lot of lenses are good in the center of the frame. They will vary more in the corners, and be worse wide-open than f8-f11. I would expect the primes might be similar, possibly the zooms similar to each other, but it's odd to have them all the same.
07-04-2011, 04:04 AM   #7
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I think you're probably about right in your assessment that the camera's resolution may be the limiting factor.

The 6.1MP sensor will have a pixel pitch of about 8 microns. Assuming you've stopped the lenses down a bit, I suppose we expect a lens resolution of at least, say, 55 line-pairs per millimetre, meaning that a line pair would occupy about 18 microns, or just over 2 pixels.

I would expect the Ricoh (assuming it's a Rikenon) and Zuiko to have the highest resolution, maybe approaching 100 lp/mm.
07-04-2011, 06:08 AM   #8
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I just realized something. The chart I used is a microscope resolution chart. I read through a few tutorials on testing camera resolution, and this just happened to be the first camera resolution tutorial that had a working link for a printable chart. It has 21 groups of lines marked between 1 and 10. All my lenses fell in between 5.6 and 6.3 or about 6 (coorelating with 6 mega pixels)? The chart is just a little down in this tutorial.
Testing Camera Lenses - Sharpness, Chromatic Aberration and Distortion - Bob Atkins Photography
I printed on a canon mp530 (office type printer but with the same print engine as the ip4300 photo printer with 9600x2400 dpi). It recommended 15x22 inch print size but I used 8.5x11 on illford smooth gloss at best settings (just an informal comparison of lenses so I figured it might be good enough). To the eye, its good to at least 8 on the chart (9 seems ok, can not tell about 10, maybe my eyes are 9 megapixel, lol).
I framed on the sides of the chart so the resolution is being tested about half way out from the center (that just happened to be the part of the frame where that resolution laid on the print).

I didn't stop the lenses down at all (I wasn't sure where to set it and since I normally use these lenses wide open that's where I tested). After the fact, I thought that stopping it down might help eliminate focus issues with the higher depth of field but didn't have time (had to put the lenses up as the kids were coming home). I just now took a couple shots with the ricoh (yes its a rikenon and so far seems to be better than any other lens I have including several AF lenses). I stopped it down to f8 (seemed to eliminate any possible focus issues), and I got the same results again.

I might have to try with the image offset so that the 5.6-6.3 groups fall on the edge of the frame (next time the kids are out). I really suspect that the camera is the limiting factor but it might be interesting to see if any of the lesser lenses are worse towards the edge.

On the field of view and crop factor thing, the way my mind is seeing it now, is that a 50mm lens see's a 50mm angle of view period. A full frame camera would have a larger image (and therefor might be perceived as having a different fov but in reality, the angle is the same, it is just taking a larger section out of the image compared to a smaller sensor). Is that about right?

07-04-2011, 06:59 AM   #9
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I took a shot close up with a macro lens and the 10 did in fact have intact lines (a bit fuzzy on the edges but clear separation of the lines). It would be interesting to see what a higher megapixel camera would do with similar lenses.
07-04-2011, 07:19 AM   #10
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Well, I can tell you now have a decent understanding of the dreaded "crop factor", but technically, I suppose, the angles are different (for the word "field" you could in fact insert "angle").

The crucial thing is, a 50mm lens is a 50mm lens on any camera, but as you're saying, the larger the sensor, the larger the FOV. And don't get confused by the P&S camera makers, who often quote "35mm equivalent" focal lengths for their products.

By the way, the 50/2 Rikenon is held by some to be one of the sharpest lenses around. I certainly think it's the sharpest in my bag (just) - but then I don't have any exotic lenses. And my camera's only 10MP, so it's probably outperformed by the lens (slightly).
07-04-2011, 08:56 AM   #11
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QuoteOriginally posted by m42man Quote

By the way, the 50/2 Rikenon is held by some to be one of the sharpest lenses around. I certainly think it's the sharpest in my bag (just) - but then I don't have any exotic lenses. And my camera's only 10MP, so it's probably outperformed by the lens (slightly).
I researched it before buying on ebay and found some saying it was the sharpest lens they had ever seen being on par with some expensive glass while others said it was good but not that good. I think the general consensus was that it varied from sample to sample and there were some that were super performers. I have a feeling I got a very good one. The second I put it on the camera, I knew it was the sharpest lens I had ever seen. It didn't require any side by side comparison. Image quality was better than any lens I had used by a decent margin. My glass is all budget glass (less than 300$ new) though I do have some decent enough auto focus lenses. 1 is rated 8 in the data base and has an average price of 120$ (mine was marked 200$ but that was new in a camera shop). Others are not in the data base (not the version I have anyway) but I gather from discussions for the versions I have that a couple are decent lenses. If nothing else some have good optics but may have other issues like build quality or AF. The ricoh blew them all away (along with beating all the MF lenses I have recently got). It beats the f.zuiko which is also supposed to be a pretty good lens (the one I have anyway).
The funny thing is, I paid 7$ shipped on ebay. It was in excellent condition (nearly new looking) with perfect/near perfect glass (hadn't really gone looking for issues but I don't even see any tiny scratches). The cheapest lens by far that I have ever got is the best (I guess you can find the rare gem cheap on ebay).
07-04-2011, 09:25 AM   #12
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Yes, they're probably still dirt cheap - amazing really, considering how good they are. Mind you, $7 for a good one is a little cheaper than normal...
07-04-2011, 11:07 AM   #13
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QuoteOriginally posted by m42man Quote
Yes, they're probably still dirt cheap - amazing really, considering how good they are. Mind you, $7 for a good one is a little cheaper than normal...
Let's see, my Rikenon 50/2 was US$6 (shipped) a few months ago, which is good, but my Rikenon 55/1.8 was a whole US$10.25. Was I robbed? And speaking of 55/1.8's -- OMFG! The Mamiya-Sekor was US$14 and the Petri CC was US$17.75! I need a lawyer!
07-04-2011, 09:20 PM   #14
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QuoteOriginally posted by RioRico Quote
Let's see, my Rikenon 50/2 was US$6 (shipped) a few months ago, which is good, but my Rikenon 55/1.8 was a whole US$10.25. Was I robbed? And speaking of 55/1.8's -- OMFG! The Mamiya-Sekor was US$14 and the Petri CC was US$17.75! I need a lawyer!
Its amazing what you can get good lenses for, especially if they are not the main stream top names, or the seller list it poorly (ends in the middle of the night on a weekday, doesn't tell what mount it is etc). I got a 500mm for a good price that was canon mount (of course I had a strong feeling that lens only came in t-mount and thats what it was). I also got 10 49mm and 10 52mm vivitar skylight filters, all new in box for 8$ shipped. Out of several lenses recently purchased, I got a couple of lemons (or good lenses in less than ideal condition) but also got several good ones cheap. I did take a few risks though. I'm guessing that the average person doesn't know that most if not all vivitar lenses have letters indicating the mount near the bottom or on the base. It blows my mind how many people don't list the mount and even don't provide a picture of it or a picture that is so blurry you cannot tell anything. Sometimes its just being in the right place at the right time (something good that no one bids on for who knows what reason).
07-04-2011, 10:18 PM   #15
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QuoteOriginally posted by ripit Quote
Its amazing what you can get good lenses for, especially if they are not the main stream top names, or the seller list it poorly (ends in the middle of the night on a weekday, doesn't tell what mount it is etc).
I like enlarger lenses on bellows. I have more than a few, including EL-Nikkor, Leitz, Rodenstock, Schneider, Novoflex, Steinheil, Eastman, etc. All but the Novoflex were under US$25 shipped; most were under US$10; some were four for US$10 shipped. Just a couple hours ago, I won an Ilex Anastigmat f/6.3 enlarging lens. No idea of the focal length. Decent but uninformative pictures. Meagre description. But I won it for 99 cents plus US$1.48 shipping, so I DON'T CARE!!! I love two-buck lenses.
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