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05-28-2009, 05:20 AM   #1
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Adapter to convert to 35mm equiv. focal length ?

Is there any adapter that will convert my lenses to the original field of view ? For example my 50mm is 80mm in APS-C and I want it to give the 35mm equivalent field of view I get in the 35mm. I don't care if I will loose an f-stop , cause obviously it will use glass elements to achieve that . I just want my 55mm f/1.2 to produce the same field of view that it does on my 35mm film camera.

Thanks !

05-28-2009, 05:33 AM   #2
axl
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In theor itshould be doable. You woul need wide angle adaptor that would ofset the 1.5 crop factor. There are some but I believe that itwould degrade IQ, not to mention the loss of light and the impracticality of having to screw the adapter on each lens. I just don't think it's wort it...
BR

PS: you can always get DA40 which equals roughly 60mm on 135 format camer
a
05-28-2009, 07:29 AM   #3
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Would a x1.5 wide-angle adaptor produce the same field of view and DOF I would get on my 35mm SLR with my 55/1.2 ?
05-28-2009, 07:37 AM   #4
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wide angle adaptors

there are a large number of wide angle adaptors on the market, and they have been available for over 25 years.

they all offer magnification ratios between 0.75 and 0.25

the market today is principally aimed at P&S cameras, or video cameras, but can be attached to an SLT lens.

I have a 0.45x that I have tried on my 24mm tamron, but the results are disappointing, and include a significant barrel distortion (fish eye effest) and loss of focus off axis.

they might be OK for a 4"x6" print but not a lot more in my opinion.

for the cost, (over $100 for most of them) you would be better off purchasing a used 35mm F2 to replace your 55mm F2.

Did I say replace? shame on me, really all you need to do is purchase the ASP-C lens witrh a FOV equal to your widest film lens today and just shift every other lens yoou use one flcal length down your list.

05-28-2009, 08:02 AM   #5
mer
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I just want the exact picture I would take ( same FOV and DOF ) with my DSLR and my 55/1.2 as I would with my 35mm film camera.

I need something like a teleconverter but the other way around.

Would a x1.5 wide angle converter produce the same FOV and DOF I get on my 35mm camera ?

Buying the 35mm F2 wouldn't produce the same DOF and in fact there is no 37mm f0.7 lens to produce the same FOV and DOF.
05-28-2009, 08:13 AM   #6
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QuoteOriginally posted by mer Quote
I just want the exact picture I would take ( same FOV and DOF ) with my DSLR and my 55/1.2 as I would with my 35mm film camera.

I need something like a teleconverter but the other way around.

Would a x1.5 wide angle converter produce the same FOV and DOF I get on my 35mm camera ?

Buying the 35mm F2 wouldn't produce the same DOF and in fact there is no 37mm f0.7 lens to produce the same FOV and DOF.
your math is a little off.

while the exact conversion is 36.6mm 35mm is the closest to that.

If you consider the change in format and the change in circle of confusion from 0.03 to 0.02 you woud winde up with a 35mm F1.4 with a DOF of .34 feet, fs the 55 mm F2 at .29 feet. close enough as far as I am concerned (all calculated at 5 feet from subject i.e. portrait distance)

not sure if any are on the market for pentax mounts, I know sigma make a 30mm F1.4
05-28-2009, 08:32 AM   #7
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I think the quick answer is yes, but long answer is nothing works well enough.
05-28-2009, 08:48 AM   #8
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QuoteOriginally posted by Lowell Goudge Quote
your math is a little off.

while the exact conversion is 36.6mm
Actually, the exact conversion of FOV from 55mm on 135 to Pentax APS-C yields 36.0mm (35.9477mm). Since claimed focal lengths are often slightly different from actual focal lengths, converting FOV to less than a whole number is pointless, so the 'exact conversion' is simply "36mm".

05-28-2009, 04:52 PM   #9
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QuoteOriginally posted by mer Quote
I just want the exact picture I would take ( same FOV and DOF ) with my DSLR and my 55/1.2 as I would with my 35mm film camera.
I would think the best you could do is a much crappier version of the exact picture - whatever lens element(s) you add to collect the wider field of view and cram it into the center of the 55mm lens is bound to degrade IQ something fierce. Certainly does with the samples I've seen (I was looking into wide adapters a while ago trying to find a cheap/small/light way to add a wide angle to my kit).

Anyhow, I'm not sure if you're just thinking of this as a thought experiment, in which case, by all means, go ahead.

But without knowing any better, I'm sort of guessing you might be new to the world of DSLR's and are assuming this would be a commonplace thing to do - that many people would be going about using adapters to get their lenses to work the same on both formats. That's just not the case. Basically, that would be like a cowboy kid turning 16, getting a new car for his birthday, then trying to figure out if there is an adapter to mount the saddle from his horse to the driver's seat of his car, or to get the car to run on hay*.

No, people normally just adjust to the fact that the two systems work differently.

[ *note: it has become my goal to work a car analogy into my posts as often as possible :-) ]
05-28-2009, 06:21 PM   #10
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Converters are pretty much a waste, but at least realize the correct numbers. "1.5X" is a telephoto converter (the opposite way of what you want). Numbers less than "1X" are the wide versions and what you want.

I'd give you mine but I already gave them away as they were unusable (at least Opteka brand is).

The best solution would be a full-frame body :-)
05-29-2009, 04:47 AM   #11
mer
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Lowell Goudge : I have a 55mm F/1.2 not a 55mm F/2 . So I would need about a 36mm f/0.7. There is not lens for pentax to reproduce the same FOV and DOF, in fact there is no 36mm F/0.7 lens for APS-C .

I don't care for big prints so I can sacrife some quality to get the same picture I get with my 55/1.2 on 35mm format.

So does anyone know any good quality wide-angle x0.7 adapters ?

I know the best solution is to get a FF camera

Marc Sabatella : Thanks. I am not really new to dSLRs. I know by adding a wide angle adapter would sacrifice quality but I don't care for big prints. I want to be able to post 900pixels width images on the internet or small prints. I was just asking because a lot of digital cinematographers use a glass element to cast the full image from 35mm lenses so it can be recorded from a much smaller sensor without too much degrading on the quality. I was wondering if there is any similar "adapter" for dSLRS and if ,in fact, is a better solution compared to wide angle adapters.


Could someone provide an example with a x0.7 wide angle adapter in front of his 50mm F/1.4 lens wide open ? I would really appreciate that .
05-29-2009, 04:51 AM   #12
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QuoteOriginally posted by mer Quote
Lowell Goudge : I have a 55mm F/1.2 not a 55mm F/2 . So I would need about a 36mm f/0.7. There is not lens for pentax to reproduce the same FOV and DOF, in fact there is no 36mm F/0.7 lens for APS-C .
sorry my misread
QuoteQuote:

I don't care for big prints so I can sacrife some quality to get the same picture I get with my 55/1.2 on 35mm format.

So does anyone know any good quality wide-angle x0.7 adapters ?
note that the wide angle adaptor changes focl length and DOF is focal length dependant so you will not get the same shot in any case
QuoteQuote:

I know the best solution is to get a FF camera

Marc Sabatella : Thanks. I am not really new to dSLRs. I know by adding a wide angle adapter would sacrifice quality but I don't care for big prints. I want to be able to post 900pixels width images on the internet or small prints. I was just asking because a lot of digital cinematographers use a glass element to cast the full image from 35mm lenses so it can be recorded from a much smaller sensor without too much degrading on the quality. I was wondering if there is any similar "adapter" for dSLRS and if ,in fact, is a better solution compared to wide angle adapters.


Could someone provide an example with a x0.7 wide angle adapter in front of his 50mm F/1.4 lens wide open ? I would really appreciate that .
i wil look at trying this
05-29-2009, 05:22 AM   #13
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QuoteOriginally posted by mer Quote
Would a x1.5 wide-angle adaptor produce the same field of view and DOF I would get on my 35mm SLR with my 55/1.2 ?
Yes-but the adapter would be called an 0.67X.

I have a Raynox 0.66X adapter which should be close enough. Photo quality is fine for modest enlargements; ok in the center but not so good at the edges.

Iowa Dave
05-29-2009, 10:31 AM   #14
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QuoteOriginally posted by mer Quote
Marc Sabatella : Thanks. I am not really new to dSLRs. I know by adding a wide angle adapter would sacrifice quality but I don't care for big prints. I want to be able to post 900pixels width images on the internet or small prints.
That much may be a reasonable thing to expect, but I don't have any way to prove or disprove that.

I guess what I don't get is, what so darn special about the FOV you got with that lens on 35mm that makes it so preferable to the somewhat *different* FOV it provides on APS-C that you're willing to sacrifice IQ to get it? Why not ask for an adapter that goes the other way around - one that could make the lens perform on 35mm the same as it does on APS-C? It seems to me that your primary concern here is the shallow DOF, and you'll get that well enough without an IQ-reducing adapter.
05-29-2009, 03:26 PM   #15
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QuoteOriginally posted by mer Quote
Is there any adapter that will convert my lenses to the original field of view ? For example my 50mm is 80mm in APS-C and I want it to give the 35mm equivalent field of view I get in the 35mm. I don't care if I will loose an f-stop , cause obviously it will use glass elements to achieve that . I just want my 55mm f/1.2 to produce the same field of view that it does on my 35mm film camera.

Thanks !
50mm f8 900 pixelswide

50mm + Raynox 6600HD (0.66x) f8 900 pixels wide


PM me if you are interested in this lens:

Iowa Dave
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