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09-04-2020, 09:20 AM   #1
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Kit lens is about 7 stops darker than others

I've just rented a K-50 for the weekend to try it out. It came with the SMC Pentax-DA L 18-55mm F3.5-5.6. I'm having a weird issue where anything I shoot through this lens is extremely dark. It shoots perfectly fine with my Pentax-a 50mm 1.7(other than the auto aperture mode letting me set the aperture in the camera but only shooting at f/22). I've also tested with an Abinar 28mm 2.8 with no issues.

I shot the following in my apartment:

50mm 1.7 @ f/4, 1/50s, 400 iso: good
28mm 2.8 @ f/4, 1/50s, 400 iso: good
18-55mm @ f/4, 1/50s, 400 iso: Only the brightest parts of the image were visible, everything else was black
18-55mm @ f/4, 1/50s, 51200 iso: Extremely grainy but as bright as the 2 with manual lenses.

Am I missing something? or is there an issue with the lens?

09-04-2020, 09:23 AM - 3 Likes   #2
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Aperture block issue?
Sounds like you got a defective rental.
09-04-2020, 09:29 AM - 1 Like   #3
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The camera most probably suffers from aperture block failure.
09-04-2020, 09:31 AM   #4
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QuoteOriginally posted by mvanorder Quote
It shoots perfectly fine with my Pentax-a 50mm 1.7(other than the auto aperture mode letting me set the aperture in the camera but only shooting at f/22).
Welcome to the Pentax Forums!

Are you saying that it also shoots dark with your Pentax-A 50/1.7? If so, I would blame the camera. I would bring the problem to the attention of the place you rented it from and suggest a refund.


Steve

09-04-2020, 09:37 AM   #5
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Tell them you'll take it off their hands as opposed to demanding the rental fee back for renting a defective camera. You have an "a" series type lenses that will work with it, not everybody does. It's absolutely insane that they shipped you a defective camera as a rental.
09-04-2020, 10:05 AM   #6
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QuoteOriginally posted by robiles Quote
The camera most probably suffers from aperture block failure.
Thanks. I looked that up(didn't know what it was). Then tested again, the aperture is closing at all settings. So basically it's shooting at f/40(about 6 1/2 stops slower than f/4 that it was set to) since there's no aperture ring on the DA lens.

I'll call the store and let them know. Since it's the only Pentax they have on hand and I need it over the weekend I'll just use my manual lenses.

---------- Post added 09-04-20 at 10:19 AM ----------

QuoteOriginally posted by stevebrot Quote
Welcome to the Pentax Forums!

Are you saying that it also shoots dark with your Pentax-A 50/1.7? If so, I would blame the camera. I would bring the problem to the attention of the place you rented it from and suggest a refund.


Steve
It's only shooting dark on the Pentax-A 50/1.7 when in auto. But as I said it's closing the aperture to f/22 regardless of what it's set to(due to the above mentioned aperture block failure).

I've called the store and let them know about the issue and that I intend to use the camera since all my Pentax lenses are manual. I'll see what they will do for me on Tuesday when I return it. One thing's for sure, I won't be buying this one from them after trying it out unless they drop the price significantly.
09-04-2020, 10:29 AM   #7
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Welcome to the forum; it's nice to have you with us.

It does sound like you may have the well-known, notorious K-30/K-50 aperture block failure. For a camera rental, I recommend you try a K-5II or K-5IIs if available. If you like it, you can find ones for sale at very reasonable prices on the PF Marketplace. I have the K-5IIs and image quality is great up to about ISO1600. Or you could try the newer K-3/K-3II. Neither of these cameras have the aperture block problem. They were both 'flagship' models; top of the Pentax line in their day. I can also recommend trying the KP. I love mine. You can get good images up to ISO6400 and even beyond. It's the newest so used prices are higher than the other two, but it's a wonderful camera. Here's a side-by-side comparison: Pentax K-5 II vs. Pentax K-3 II vs. Pentax KP - Pentax Camera Comparison - PentaxForums.com

The K-70 model can take excellent images from what I've seen here on PF. There's been a small amount of talk about whether or not this model can suffer from aperture block failure, but I think the jury is still out on that issue. K-70 owners can chime in with their experiences.

I hope you find a model that suits your needs and budget. At some point you may want to consider upgrading from the SMC Pentax-DA L 18-55mm F3.5-5.6 lens. I went from the 18-55mm to a Sigma 17-70mm DC Macro that I got used at a great price. It provided a major upgrade in image quality. Others will have their own recommendations of course.

I'm just down the road in Goldsboro.
09-04-2020, 10:46 AM   #8
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QuoteOriginally posted by mvanorder Quote
But as I said it's closing the aperture to f/22 regardless of what it's set to(due to the above mentioned aperture block failure).
Are you sure?

If the aperture ring is set to f/1.8 and it is stopping down to a narrower aperture, then the problem is with the lens. You can test this with the lens off the camera. Aperture block failure on the K-50 results in the actuator lever doing full travel regardless of the camera setting. With the aperture ring on your 50mm on other than "A" and the camera in "M" or "B" modes, the lens should stop down the same as on a film camera even if there is aperture block failure.*


Steve

* Assuming aperture ring is set to "enable" in the menu custom settings.

09-04-2020, 10:54 AM   #9
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QuoteOriginally posted by Apet-Sure Quote
Welcome to the forum; it's nice to have you with us.

It does sound like you may have the well-known, notorious K-30/K-50 aperture block failure. For a camera rental, I recommend you try a K-5II or K-5IIs if available. If you like it, you can find ones for sale at very reasonable prices on the PF Marketplace. I have the K-5IIs and image quality is great up to about ISO1600. Or you could try the newer K-3/K-3II. Neither of these cameras have the aperture block problem. They were both 'flagship' models; top of the Pentax line in their day. I can also recommend trying the KP. I love mine. You can get good images up to ISO6400 and even beyond. It's the newest so used prices are higher than the other two, but it's a wonderful camera. Here's a side-by-side comparison: Pentax K-5 II vs. Pentax K-3 II vs. Pentax KP - Pentax Camera Comparison - PentaxForums.com

The K-70 model can take excellent images from what I've seen here on PF. There's been a small amount of talk about whether or not this model can suffer from aperture block failure, but I think the jury is still out on that issue. K-70 owners can chime in with their experiences.

I hope you find a model that suits your needs and budget. At some point you may want to consider upgrading from the SMC Pentax-DA L 18-55mm F3.5-5.6 lens. I went from the 18-55mm to a Sigma 17-70mm DC Macro that I got used at a great price. It provided a major upgrade in image quality. Others will have their own recommendations of course.

I'm just down the road in Goldsboro.
Thanks for the pointers. As for the lens, it's just the kit lens with the rental. If I bought one having an automatic zoom lens would be nice, but over the past few months I've picked up 6 primes(5 usable currently) and 3 zooms, of which all are manual. At the moment those are being used on a K1000 and MG I picked up on ebay "as-is untested" in working order. My only DSLR is a 6MP Nikon D40, so Looking to get a DSLR for my lenses that's an upgrade from 6MP. I've been looking for a KP(can't hardly find them for sale used), K-70, or K-S2. The K-S2 I occasionally see deals around $300 for used in good condition, so it's hard to justify spending $700 on a KP body only when it's just a hobby.
09-04-2020, 11:52 AM   #10
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For the price, a low-use K-5 IIs is hard to beat. I still sometimes use mine and like it, even though having the latest- the KP as my main body. Neither of these is subject to developing the aperture block problem.
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